synergy effects of the indian summer monsoon and...

Research ArticleSynergy Effects of the Indian Summer Monsoon and the TibetanPlateau Heating on Summer Rainfall over North China

Siwen Zhao 1 Jie Zhang 1 and Zhihong Lv 2

1Key Laboratory of Meteorological Disaster Ministry of Education (KLME)Joint International Research Laboratory of Climate and Environment Change (ILCEC)Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD)Nanjing University of Information Science amp Technology Nanjing 210044 China2Fushun Meteorological Bureau Fushun 113000 China

Correspondence should be addressed to Jie Zhang gs-zhangjie163com

Received 11 September 2019 Accepted 4 February 2020 Published 19 March 2020

Academic Editor Ismail Gultepe

Copyright copy 2020 Siwen Zhao et al is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

An analysis based on July-August precipitation reveals that there is a tripole pattern of the precipitation distribution that issignificantly increased rainfall over North China (NC) is related to the increased rainfall over the Indian subcontinent (IS) and thedecreased rainfall over the southeastern Tibetan Plateau (TP) and vice versa that corresponds to the Indian summer monsoon(ISM) and TP heating pattern which are interactive erefore it is necessary to investigate the effect of NC rainfall-relatedatmospheric circulation and the physical linkage with the two thermal forcings together e linear baroclinic model (LBM) isapplied to determine the dynamics of the process e results show that an enhanced ISM is accompanied by reduced TP heatingfavors convection and easterly anomaly over the IS and produces a Gill-type Rossby wave that affects the vorticity over NorthAfrica Meanwhile there is another Rossby wave originating in North Africa and moving eastward to the Pacific Ocean whichinterferes with circulation at mid- to high-latitudes ie it strengthens the cyclone over the Baikal region and stretches the westernPacific subtropical high (WPSH) northward to northeastern Asia and results in abundant water vapor transported to NCFurthermore the strong convection over the IS excites the Kelvin waves over the equatorial region which moves eastward andgenerates anticyclones over Philippines consequently leading to the Pacific-Japan (PJ) patterne PJ pattern cooperates with thewave train at midlatitudes resulting in abundant water vapor being transported to NC e summer rainfall over NC is thereforemodulated by synergistic effect of both the ISM and TP heating

1 Introduction

North China (NC) is located at mid-to high-latitudes be-tween the Baikal region and the northwestern Pacific Oceanthe climate variability here in summer is very large and isaffected by atmospheric circulation anomalies such asblockings at high-latitudes over both the tropical andextratropical regions [1] westerly wave trains [2] westernPacific subtropical high (WPSH) [3] and Asian summermonsoons [4ndash6] NC is a densely populated resource-richand economically developed region in China and has a greatdemand for water [7] Summer precipitation contributesmore than 70 of the annual total precipitation in NC [8]

and exhibits substantial interannual to decadal variationsresulting in more sensitivity to water shortages erefore itis essential to predict the precipitation over NC

e precipitation variability in NC is closely related tostationary external Rossby waves [9 10] that are excited bydivergence caused by orthography and thermal forcing [11]and quickly disperse along the westerly jet stream [12]further affecting the global atmospheric circulation anom-alies However the effect factors at mid-to high-latitudes arecomplex and diverse and the wave trains in extratropicalregions are considered to be responses to the tropical heatinganomalies [13 14] Many studies thus focused on the heatingsources in the tropics such as the Indian summer monsoon

HindawiAdvances in MeteorologyVolume 2020 Article ID 8395269 16 pageshttpsdoiorg10115520208395269

(ISM) and suggested that increased precipitation over theIndian subcontinent (IS) played an important role in theboreal atmosphere during summer

Many previous publications have focused on the rela-tionship between precipitation over NC and the ISMKripalani and Singh [15] noted that the rainfall over NC ishighly related to rainfall over India and suggested to take thesubtropical ridge over the Indian region as an importantpredictor over India as well as over NC Wang et al [16] andDing and Wang [9] commented that the rainfall showssynchronous anomalies over the IS and NC during summerLiu and Ding [17] also utilized the model to simulate theprecipitation teleconnection between India and NorthChina Various studies documented that the ISM affected thesummer climate in East Asia through a midlatitude wavetrain along the East Asian upper tropospheric westerly jetstream causing differences in atmospheric circulation andwater vapor transport [18 19] e results further revealedthat an enhanced ISM could generate anomalous cycloniccirculation over the Mediterranean Sea in the upper layer[20 21] and stimulated a continuous downstream air flowie a silk road pattern [22] with a barotropic anticyclonicanomaly over East Asia leading to more water vapor beingtransported northward along the western periphery of theWPSH [23] However the position and intensity of the ISMwhich lead to precipitation over NC exhibit large vari-abilities in addition to land-sea thermal contrasts and areaffected by atmospheric internal dynamic processes [24] andEl Nintildeo-Southern Oscillations (ENSO) [25] e thermalforcing of the Tibetan Plateau (TP) also plays a decisive rolethrough air pumping [26ndash28] Moreover the TP also has aconsiderable influence on the boreal circulation and pre-cipitation as a significant surface and atmospheric heatingsource in summer [29 30] which therefore is alsoconsidered

e change in TP diabatic heating especially latentheating released by rainfall in summer has a profoundinfluence on the seasonal circulation and the interannualchanges of the Northern Hemisphere [31] and it has con-siderable influence on the precipitation over NC during thesummer time Observational studies have shown that in-creased TP heating can intensify East Asian summermonsoons which contribute to the upward trend of mon-soon rainfall over NC [32 33] Heating on the TP will triggertwo waves One wave travels downstream along the westerlyjet stream and the other wave spreads along the low-levelsouthwesterly monsoon flow to the South China Sea [34]e west one results in an anticyclone over NC leading toless precipitation there [35]

Despite the effect of TP thermal forcing on the ISM theISM can also affect summer rainfall over the TP over a widerange of time scales [36 37] which is modulated by at-mospheric processes over the midlatitudes [38] and in-coming water vapor transport [39 40] further affecting thethermal condition of the TP

Prior to the current study of precipitation over NC moststudies have typically involved only one single influencefactor because it is difficult to identify the main influencingfactors which vary but may not be considered Because of

the interactive relationship between the TP thermal forcingand the ISM it is reasonable to regard both as one phe-nomenon or to assume that they are one system Addi-tionally the investigations on the role of tropical heatinghave been limited to only revealing the correlation thus themechanism is unclear

Based on the above discussions the objectives of thisstudy were to determine the precipitation distributionpattern during summer investigate the effect of the ISM andTP heating on the precipitation over NC and utilize a modelto understand the mechanism is paper focuses on thevariability of the midlatitude wave train which will help tointerpret extratropical responses to the tropical heatinganomalies in Asia Amore practical motivation for this studyis that the precipitation over NC can be fully and accuratelypredicted

e structure of this paper is as follows Section 2 de-scribes the data and methods Section 3 shows the tripolepattern distribution and the related circulation In Section 4we describe the model experiments performed to obtain thecirculation response to different forcing Section 5 presentsthe wave activity flux to analyze the propagation of the waveBrief conclusions and discussions are provided in Section 6

2 Materials and Methods

In this study we focused on the concentration period (July-August JA) of summer rainfall when the precipitation modeis most typical and a wave-like pattern is also often observedover Eurasia

e following datasets were used in this study (1) edaily precipitation data (APHRO) were derived from theAsian Precipitation -Highly-Resolved Observational DataIntegration towards Evaluation of the Water Resources(APHRODITE) e subset of APHRO covered MonsoonArea (60degN-150degN15degS-55degN) APHRO_MA_V1101 wasused e product includes daily rainfall from 1951 to 2007with a spatial resolution of 025deg times 025deg e APHRO rainfallshows fair applicability in the TP and surrounding areasbecause of its high resolution and improvement in inter-polation [41] To verify the results the global rainfall datasetthe Global Precipitation Climatology Centre monthly(GPCC) mean rainfall data was derived from the NationalOceanic and Atmosphere Administration (NOAA) at aresolution of 10deg times10deg and the data were chosen for theperiod of 1901ndash2013 (httpwwwesrlnoaagovpsd [42])Monthly mean rainfall from the Global Rainfall ClimatologyProject (GPCP) analysis dataset version 23 from 1979 to2017 (httpgpcpumdedu [43]) was used (2) e Eu-ropean Centre for Medium-Range Weather Forecasts(ECMWF) Interim Re-Analysis monthly atmospheric re-analysis data included geopotential height and zonal andmeridional winds at 200 hPa 500 hPa and 850 hPa on a15deg times15deg grid for 1979ndash2017 which were obtained from theECMWF (httpappsecmwfintdatasets [44])

e main statistical tools used in this study includedempirical orthogonal function (EOF) analysis correlationanalysis and regression analysis Linear trends were re-moved from all the data before the regression and

2 Advances in Meteorology

correlation analyses were performed e North test wasused to examine the stability of each EOF [45] Studentrsquos ttest was performed to calculate the significance in thecorrelation and regression analyses

In this paper the inverse algorithm was used to calculatethe apparent heat source (Q1) and apparent moisture sink(Q2) of the atmosphere from 1979 to 2017 which could beobtained from the following formula [46]

Q1 Cp

zT

zt+ V

rarrlowastnablaT +

p

p01113888 1113889

κ

ωzθzp

1113890 1113891

Q2 minusL

Cp

zq

zt+ V middot nablaq + ω

zq

zp1113890 1113891

(1)

where κRCp R is the dry air Gas constant Cp is thespecific heat at constant pressure θ is the potential tem-perature t is the temperature q is the mixing ratio of watervapor v is the horizontal wind and L is the latent heat ofcondensation Term Q1 represents the heating rate of air perunit mass in unit time and term Q2 represents the heatingrate caused by the heat released by condensation of watervapor per unit mass in unit time In this paper the inte-gration height from the ground (surface pressure PS) to thetop (100 hPa) of the convection layer was chosen Q1 wasused to represent the integrated atmospheric apparent heatsource andQ2 was used to represent the integrated apparentmoisture sink When water vapor decreased due to con-densation the latent heat is released and Q2 was positiveotherwise it was negative

e numerical experiments performed in this study werebased on the linear baroclinic model (LBM) that was de-scribed in detail in Watanabe and Kimoto [47 48] Manystudies show that the LBM is a useful tool to diagnose howthe atmosphere dynamically reacts to the prescribed forcingwhich is in general agreement with observations [19 49] Toclarify the role of dynamic processes we utilized the dryLBM based on time integration of the linear model withrealistic orography e resolution used here was a trian-gular truncation of 42 waves (T42) and its horizontal res-olution was approximately 28deg times 28deg with 20 equally spacedsigma levels (L20) e basic background state of the ex-periment was the JA climate average field of the ERA-In-terim data for 1979ndash2017 e boundary conditions andinitial conditions were determined by the model An im-portant feature of the model was that the time integrationwas set at up to 30 days because the response approached asteady state near day 15 to 20 Here we took the day 15 assteady results

3 Observed Linkage among Rainfalls over theIS TP and NC

31 Rainfall Tripole Pattern in Summer time To identify therainfall distribution patterns we applied EOF analysis to thecovariance metric of JA precipitation Figure 1(a) shows theleading rainfall variability pattern over Asia based onAPHRO data e leading mode (EOF1) accounts for 151of the total variance and is well separated from the other

modes evaluated by the North test e pattern (shown asldquo+minus+rdquo in Figure 1(a)) is a tripole pattern that extends fromthe IS across the southeastern TP to NCis tripole patternis available when the EOF analysis is applied to the GPCCrainfall data from 1940 to 2013 (Figure not shown) and it isdefined as an IS-NC pattern by Zhang et al [50] eprincipal component corresponding to the leading spatialpattern (PC1) is shown in Figure 1(b) which indicates thetripole pattern rainfall has discernable interannual variationssuperposed upon it To facilitate our analysis we define theIS rainfall index (ISR) as the normalized area average rainfallin the region of 75degEndash85degE 20degNndash26degN in JA with the NorthChina rainfall index (NCR) for the domain of 107degEndash120degE37degNndash44degN and the rainfall index of the southeastern TP(TPR) is defined over the region of 85degEndash95degE 28degNndash31degNe simultaneous rainfall associated with the ISR features asignificant distribution as mentioned above e tripolepattern is still significant when the GPCC data are applied tocalculate the correlation of ISR with rainfall (Figure 1(c))e negative correlation center of precipitation in TP is inthe southeastern foot of the mountain just the region wepicked In addition we notice that there are also obviouspositive correlation areas with ISR in Southeast Asia fromFigures 1(a) and 1(c) It may be related to the water vaporchannel under this pattern and will be discussed laterFigure 1(d) displays the time series for the ISR (the blacksolid line) the NCR (blue dashed line) and the TPR (the reddashed line) e out-of-phase relationship of rainfall be-tween Indian monsoon and NC is a well-known telecon-nection pattern and the correlation coefficient betweenNCR and ISR is 030 while minus016 is not significant with TPRWhat role does the TP play en we calculate the corre-lation coefficient between the ISR and the TPR which isminus06 and it supports the point that they are synergistic andaffect the climate in NC

e ISR exhibits a reverse variation with precipitationover the southeastern TP implying a reverse latent heatdistribution e latent heat of condensation associated withthe large amount of rainfall in both the IS and the TP plays avital role in driving the atmosphere circulation in northernhemisphere [27] us to determine the underlying reasonfor the tripole pattern and its effect we examine the asso-ciated atmospheric circulation anomalies in Section 32

32 AssociatedAtmospheric Circulations Figure 2 shows theregression patterns of the atmospheric circulation andrainfall onto PC1 When PC1 is positive precipitation in-creases in the IS and NC corresponding to weakened SouthAsian High (Figure 2(a)) ere are strong anticyclonicanomalies near Central Asia which indicates strong di-vergence e basic distribution of summer circulation isshown in Figure 2(b) as contours ere are obvious troughand ridge activities in the westerly belt and the WPSH isabout 30degN in latitude In the mid-troposphere (Figure 2(b))the WPSH is significantly northwestward there are obviouswesterly anomalies in NC with warm and wet air trans-ported Meanwhile the negative anomaly near Lake Baikaldeepens the trough and transports dry and cold air from

Advances in Meteorology 3

Siberia to NC ere are divergence anomalies over the TPand the wind speed is small which is coherent with Jiang[37] In northern India the westward flow is obvious ereare significant cyclonic anomalies leading to the increase ofconvection As for term of water vapor transport it is ba-sically consistent with the distribution of precipitationanomalies (Figure 2(c)) One branch of water vapor istransported from the cross-equatorial airflow to India andanother branch is transported to India around the northerntopographic line of the TP from the Bay of Bengal whilethere is less water vapor to the TP corresponding to lessprecipitation ere is also significant water vapor trans-ported to NC To further illustrate circulation anomaliesrelated to rainfall in these three regions we compare theregressed atmospheric circulation anomalies against theNCR TPR and ISR as shown in Figure 3

Figure 3(a) shows the regression map of atmospherecirculation with regard to the simultaneous NCR which isrelated to ascending precipitation over NCere is a well-organized zonal wave train spanning from Central Asia tothe Pacific Ocean with anomalous anticyclones in theMediterranean Central Asia and Northeast Asia

separated by cyclonic anomalies e anomalous cyclonestrengthens the trough and conveys cold dry air into NCBesides the anomalous anticyclone over Northeast Asia isconducive to the WPSH northward and causes moremoisture transported to NC consequently leading to thenorthward shifting of the distribution of precipitation inEast China Moreover the anomalous anticyclone di-verged over the TP in the lower troposphere (Figure 4(a))suggesting a decrease in precipitation because thesoutherly movement and convergence are significant forincreased rainfall in the tropics since the air temperature isrelatively uniform in the tropics while the subtropical areais even warmer in summer Figure 3(b) shows the in-creased precipitation in the southeastern TP ere is anappearance of robust negative anomaly over Central Asiaand East Asia and between them is a positive anomaly overthe southern Baikal region providing less water vapor forNC Moreover the anomalous anticyclonic circulationover South China indicates a strengthened WPSH tendingsouthwards with more moisture led by lower-tropospherewind gathers in South China as shown in Figure 4(b) isprecipitation distribution agrees well with the ldquosouthern

50N

40N

30N

20N

IS

TP

NC

141

80E 100E 120E

ndash03 ndash02 ndash01 0 01 02 03

(a)

30201000

ndash10ndash20

1980 1990 2000 2010

(b)

80E 100ECONTOUR FROM ndash05 TO ndash08 BY 01

120E

50N

40N

30N

20N 4

0

0

0

0

2

ndash2

(c)

30201000

ndash10ndash20ndash30

1980 1990 2000 2010

TPRNCRISR

(d)

Figure 1 (a) Spatial pattern of the first EOF analysis applied to July-August (JA) APHRODITE rainfall from 1951 to 2007 (b) Principalcomponent corresponding to spatial pattern in (a) (c) Geographical distribution map of the correlation coefficients between JA GPCCrainfall from 1940 to 2013 and the India Subcontinent Rainfall (ISR) dark (light) shadings indicate values exceeding 99 (90) confidencelevels through studentrsquos t test (d) e time series of the ISR (red dashed line) rainfall over North China (NCR) (blue dashed line) andsoutheastern Tibetan Plateau Rainfall (TPR) (black solid line)


flood-northern droughtrdquo pattern [51 52] Moreover the ISis occupied by an anomalous anticyclone which favors thetransportation of the water vapor northward (Figure 4(b))combined with the water conveyer belt from the Bay of

Bengal it is remarkably conducive to precipitation overthe southeastern TP but useless for the IS e anomalouscirculation for increased rainfall over the IS is shown inFigure 3(c) It is very similar to the result in Figure 3(a) in

1

0 30E 60E 90E 120E 150E 1800

20N

40N

60N

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

CA

CA

1


(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

ndash2 ndash15 ndash1 ndash05 0 05 1 15 2

15

(c)

Figure 2 e linear regression pattern of the (a) 200 hPa wind (vectors units mmiddotsminus1) (b) e linear regression pattern of 500 hPageopotential height (shadings units gpm) 500 hPa wind (vectors units mmiddotsminus1) and climatic JA 500 hPa geopotential height (contoursunits gpm) (c) e linear regression pattern of water flux (vectors units kgmiddotmminus1middotsminus1) on the PC1 during 1979ndash2007 Dark (light) stipplingindicates values significantly exceeding the 99 (90) confidence level using Studentrsquos t test in (b) and (c) winds with values under the 90confidence level are omitted in (a)ndash(c)

0

30N

60N

A CA

C A

1

0 30E 60E 90E 120E 150E 180

ndash100 ndash50 0 50 100

(a)

0

30N

60N

C C

1

0 30E 60E 90E 120E 150E 180


(b)

0

30N

60N

A CA

CA

1

0 30E 60E 90E 120E 150E 180


(c)

Figure 3 e linear regression pattern of the 500 hPa geopotential height (shadings units gpm) and 500 hPa wind (vectors units mmiddotsminus1)against the (a) NCR (b) TPR and (c) ISR for JA during 1979ndash2007 Dark (light) stippling indicates values significantly exceeding the 99(90) confidence level using Studentrsquos t test


the key areas anomalous cyclone in Baikal area enhancedsouthwestern airflow in NC anomalous anticyclone inCentral Asia cyclone anomalies in the IS and anticycloneanomalies in northern Africa all of which are consistentwith those discussed above on the one hand they areconducive to precipitation in the IS on the other hand thedivergence is conducive to the generation of Rossby waveand further affects climate in NC through wave train onlythe positive anomaly is more obvious and broader insubtropical Pacific (Figure 3(c)) Meanwhile there is anortherly air flow over the TP in the lower troposphere asshown in Figure 4(c) implying an increase in precipitationover the IS but a decrease in precipitation over the TP It isworth noting that there is an anomalous anticyclone overPhilippines in Figures 3(a) and 3(c) just like Figure 2(b)

At middle latitude and over India the circulation isbasically the same when precipitation increases in NC andIS at is Central Asia Lake Baikal and Northeast Asiacorrespond to ldquo+minus+rdquo anomaly centers India corresponds tonegative anomaly contrary to the increase of precipitation insoutheastern TP e results further confirm the rationalityof the tripole pattern which is related to circulation at lowlatitudes and mid- to high-latitudes us in Section 4 wediscuss the determination of the physical mechanism andhighlight the tropical thermal forcing

4 Possible Teleconnection Linking theSynergetic Diabatic Heating Effect

In the above discussion we addressed the tripole pattern forrainfall over the IS and the southeastern TP and NC eincreased precipitation over the IS caused by strengthenedISM is often accompanied by the release of latent heatingsimilar to that in the southeastern TP [53] which means thatthe diabatic heating can represent precipitation to a large

extent erefore we use the LBM to verify the effect ofthermal forcing and investigate how it determines therainfall distribution Based on the tripole pattern distribu-tion shown in Figure 1 we consider two forcings heatingover IS and cooling over TP represent the enhancement ofthe ISM and the abatement of the TP heat Q1 and Q2 arebasic quantities for diagnosing the mechanisms of theheating process e large centers of Q1 and Q2 correspondwell with the heavy rainfall center of the same period of thetime e observed results of average Q1 and Q2 over the ISand TP are given in Figure 5 to make clear the profile of thediabatic heating in JA It is shown that the level of thestrongest heating is lower over the southeastern TP than ISe climatic TP heating is generally near the ground whilethe center is around 700 hPa over IS We also separate thestrong and weak ISM year with the 90th percentile andcalculate the difference value as shown in Figures 5(b) and5(d) the maximum value of the TP is around 500 hPa andaround 800 hPa of the ISe average surface pressure of theclimate in the southeast of the TP in summer is around600 hPa while that in India is around 1000 hPa With theconsideration of Q1 and Q2 above we consider the changesin air heating rate caused by the two forcings are in themiddle troposphere and the bottom troposphere respec-tively All these forcings have horizontal shapes that areelliptical with zonal radii of 5 degrees andmeridional radii of2 degrees e in-depth mean and the vertical structure ofthe forcing are shown in Figure 6 e two forcings re-spectively represent the variations of the diabatic in the ISand southeastern TP And they are set to 1Kday just as thevalue in Figures 5(b) and 5(d) We performed four exper-iments (1) INH the idealized diabatic heating over India at80degE 22degN with the center at 045 (Sigma coordinate system)(2) TPC the idealized diabatic cooling at 90degE 30degN with thecenter level at 095 (3) TPH same as TPC but for heating

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(a)

0

30N

60NA

3

C

C

C

0 30E 60E 90E 120E 150E 180

(b)

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(c)

Figure 4 (a) Regression maps of 850 hPa wind (vectors units mmiddotsminus1) anomalies against (a) NCR (b) TPR and (c) ISR for JA during1979ndash2007 Dark (light) shadings indicate values significantly exceeding the 99 (90) confidence level using Studentrsquos t test


instead of cooling and (4) COM the combined forcing ofINH and TPC

We performed the INH and TPC experiments to isolatethe effect of the two thermal forcings and further illustratedtheir synergetic effect e results are shown in Figure 7which are completely different for the two experiments

For the INH experiment there is an apparent wave trainat mid- to high-latitudes with four positive anomalies at200 hPa (Figure 7(a)) distributed over northern AfricaCentral Asia and northern Bohai Sea and there are three

relatively weak negative anomalies in the northern Medi-terranean Sea the Baikal region and the northwest PacificOcean It is barotropic at mid- to high-latitudes in INH andthe wave train is known to be maintained by the conversionof the kinetic energy of the westerly jet stream throughbarotropic instability e positive anomaly over East Asia isconducive to reinforcing the WPSH and moving northwardresulting in abundant water vapor but inadequate upwardmotion in NC In the tropics the height field of 200 hPa issymmetrical near the equator (Figure 7(a)) which may have

0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)

Figure 5 Profile of (a) climatological and (b) composite difference between the strong and weak ISM years of JA apparent heat source (Q1)and apparent moisture sink (Q2) (units kmiddotdayminus1) of the atmosphere from 1979 to 2017 Black circles indicate values significantly exceedingthe 90 confidence level in (b) and (d)


triggered a Gill-type Rossby wave [54] e Rossby waveforced by tropical thermal forcing could have been self-maintained via thermal damping characterized by a warmtemperature anomaly moving westward in the lower layerand a cold temperature anomaly moving eastward in theupper layer over West Asia (figure not shown) [55 56] Asshown in Figure 7(b) there is a strong vertical shear of theeasterly wind in North India which increases the monsoonconvection leading to an increase in precipitation on thedownshear and to the left and traps the Rossby wave in thelower troposphere In addition the diabatic heating asso-ciated with monsoon rainfall represented a strong forcing tothe atmosphere [18 21] leading to strengthened convectionover the IS e latent heating released by the increasedrainfall along with the land-sea thermal contrast leads tomore water vapor transport from the Southern Hemisphereand the Arabian Sea to IS as shown in Figure 7(c) And it iscoherent with the results by Greatbatch [19] in which it isinterpreted that Kelvin waves appear on the Indian coast and

spread eastward (Figure 7(c))e Kelvin waves facilitate theinland transport of water vapor from the Bay of Bengal to thenorth and also inhibit the convection over the PhilippineSea and the Pacific-Japan (PJ) teleconnection appears thusstrengthening the anticyclone over Japan Additionally itshould be noted that it is baroclinic in low-latitudes except inthe Sahara Desert as shown in Figures 7(a)ndash7(c) e SaharaDesert in Africa has a strong heating effect and generates aneasterly jet stream [57 58] with a cyclonic shear on the southside which can form a weather scale disturbance thatpropagates westward In addition it is important to note thatthere is also an external Rossby wave that propagateseastward along the westerly jet stream at mid- to high-lat-itudes corresponding to the upper divergence over theNorth Africa

In summer the thermal forcing of the TP has a greaterimpact on the Northern Hemisphere circulation than thetopography [38 59] e cooling at the surface may lead toweakened convection and result in less precipitation To

60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08

1000 ndash02 ndash04 ndash06 ndash08 ndash10 ndash12

Kday

(c)

Figure 6 e (a) in-depth mean of diabatic heating anomalies in 80degE 22degN and cooling anomalies in 90degE 30degN (units Kmiddotdayminus1) andvertical profiles of forcing (units Kmiddotdayminus1) in (b) 80degE 22degN and (c) 90degE 30degN used to drive the LBM model


determine the decrease in precipitation over the south-eastern TP we performed the TPC experiment and theresults are shown in the right side of Figure 7

At the upper layer (Figure 7(d)) the negative anomaly ismore obvious on a large scale and spans almost all of Asiaexcept for the area west of Central Asia ere is a Rossbywave train at the midlatitudes moving along the westerly jetstream in the midlayer (Figure 7(e)) e anomalous cyclonein the Baikal region is stronger in the TPC e anomalouscyclone increases the intensity of the trough but has thedisadvantage of northward movement of the WPSH asshown in Figure 7(e) Moreover an anomalous barotropicanticyclone has formed downstream from the cyclone over

the Japan Sea e water vapor is mainly concentrated in theYangtze River basin but poor in NC Furthermore it gen-erates a cyclonic anomaly in the upper troposphere over theTP which weakens the South Asian High suggesting adecrease in precipitation over the TP

erefore both the two circulations against the twothermal forcings not only affect the local circulation but alsoaffect the remote region e responses to the strengtheneddiabatic heating over the IS are characterized by the for-mation of a wave train with a barotropic structure at themilatitudes a tropical Rossby wave easterly anomaliesKelvin waves at low-latitudes and PJ pattern in the PacificNC is at the center of positive anomalies e significant

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

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0

30N

60N

Day15

ndash20

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ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )

Figure 7 (a) Steady 200 hPa height anomalies (contours unit gpm) (b) 500 hPa height (contours unit gpm) and winds (vectors unitmmiddotsminus1) anomalies and (c) 850 hPa winds anomalies (vectors unit mmiddotsminus1) generated by INH experiment (d)ndash(f ) is as (a)ndash(c) but for TPCexperiment


characteristics of TP cooling include an enhanced negativeanomaly over the Baikal region a southwestwardWPSH anda weakened air-pumping effect ere are negative anom-alies in East Asia Moreover these two forcings lead to watervapor being transported along different paths resulting indifferent effects on the precipitation over NC us wedesigned the COM experiment to clearly determine thephysical mechanism based on the tripole pattern shown inFigures 1 and 2 e time evolution diagram of the responseis shown in Figure 8

Figure 8 shows the circulation anomaly responses for theCOM experiment at 500 hPa for days 1ndash15 On the 1st dayheating over the IS triggered an anomalous anticyclone insitu while cooling over the southeastern TP produced ananomalous local cyclone (Figure 8(a)) On the 5th day theoriginal positive anomalies over India weakened substan-tially and moved eastward while the negative anomaly overthe TP and expanded to the southern Central Asia rangesover the TP generating a divergence with a positive anomalyin the north (Figure 8(b)) On the 10th day when the cir-culation basically formed the divergence wind that appearedon 5th day developed an anomalous anticyclone in CentralAsia which may trigger the Rossby wave As shown inFigure 9(a) it was symmetrical in Africa generating a Gill-type Rossby wave It was coherent with the suggestion by Linet al [20 60] that the response over Europe was related to theequatorial Rossby wave response to ISM heating e Gill-type Rossby wave induced the divergence over the NorthAfrica in upper troposphere which could induce the sta-tionary Rossby wave e influence of the two thermalforcings at the midlatitudes created two branches of theRossby wave train including the ldquo+minus+rdquo anomalies patternobserved in West Asia the Baikal region and northwesternPacific Ocean over the subtropical regions similar patternsexisted from the midlatitudes to the equator When theresponse was stable on the 15th day the Kelvin waves inIndia were particularly pronounced with an anomalousanticyclone over the Philippine Sea and a strengthened watervapor transport to inland (Figure 9(b)) Meanwhile therewas abundant water vapor in South Asia It meant the watervapor in the Bay of Bengal transports to South Asia apartfrom converging in the IS On the one hand it increasedprecipitation in South Asia on the other hand it also in-creased water vapor of the water conveyer belt from theSouth China Sea to the north e anomalous cyclone overthe IS however caused water vapor to pass through theinland and then to the TP leading to a deficiency in watervapor And the positive anomalies over the TP also led theSouth Asian high westward with a decreased precipitationover the TP Furthermore the Kelvin waves also suppressedthe anticyclonic convergence over the northern Philippinesand induced the PJ pattern

Based on the simulated and the observed results dis-played above when the response was stable the Kelvinwaves led by an anomalous anticyclone over the PhilippineSea and a strengthened water vapor transport to inland(Figure 9(b)) is also has an important impact on summerprecipitation in NC and it is necessary to explore the effectof the PJ teleconnection pattern on the precipitation in NC

In this paper the PJ pattern is defined by the EOF e850 hPa relative vorticity field in the East Asia-NorthwestPacific region (0ndash60degN 100degEndash160degE) [61ndash63] is calculatedCompared with the traditional definition method the one-point correlation regional EOF is more objective and theatmospheric variables in 850 hPa are less affected by to-pography and are closely related to convective precipitationthus it is more accurate en the relative vorticity anomalyis regressed to the principal component (PC1) corre-sponding to the leading spatial pattern of EOF which is wellseparated from other modes e obtained relative vorticityregression map presents a distinct meridional wave train inthe East Asia-Pacific region that is PJ teleconnection pat-tern as shown in Figure 10(a) and it is consistent with resultsof Kosaka et al [63] e PC1 is defined as PJ teleconnectionpattern index (PJI) e correlation coefficient between PJIand ISR 035 is significantly a positive correlation It isconsistent with the conclusion above that the strengtheningof ISM causes the Kelvin waves and it further induces the PJpattern is paper mainly focuses on the pattern distri-bution as negative-positive-negative relative vorticity innorthern Philippines Japan Sea and Okhotsk Sea(Figure 10(a)) corresponding to the strong ISM case e PJpattern has a reinforcing effect on the COM results resultingin the negative vorticity anomaly in the south strengthenedand northwestward leading to the positive vorticity centeroccupying the NC Meanwhile the PJ pattern has a sig-nificant correlation with precipitation in China(Figure 10(b)) and the distribution of rain belt and vorticityanomalies is basically coherent Under the joint effect ofmidlatitude wave train and PJ pattern (+minus+ in 500 hPafigure not shown) the positive anomaly is strengthened andmoves northwestward thus leading the WPSH moving bythe same path which is conducive to water vapor transport

Compared with the two separate experiments discussedabove (INH and TPC) the response of the COM experimentin the tropical region is almost the same as that of the INHexperiment whereas it is considerably adjusted at themidlatitudes because of TP cooling e negative abnormalcirculation is entrenched in the Baikal region and thepositive anomaly in East Asia is extended farther westwardand more broadly With the cooperation with PJ pattern thejunction of positive and negative height anomalies is justlocated in NC corresponding to an anomalous cyclone at850 hPa suggesting a strengthened upward movement(Figure 9(b)) is result also provides support for theWPSH with northward shifting with abundant water vaporfrom the western tropical Pacific Ocean to NC

e circulation is in agreement with the regressed cir-culation against NCR in Figure 3(a) ie that type of cir-culation indeed leads to increased precipitation over NC Italso shows that it is indeed the synergistic effect of the twoforcings to affect the summer precipitation in NC In thissubsection the sequence of emergence of each system isexplained and the rationale for the tripole pattern is de-scribed e next step is to investigate the relationshipamong the anomalous circulations how tropical forcingaffects the circulation at mid- to high-latitudes and how itfinally influences the precipitation over NC


5 Investigation of the Physical MechanismsBased on Wave Energy Propagation

Although Figure 9 provides the development of the cir-culation we still do not determine the propagation of thewave train erefore we calculate the Takaya and Naka-mura wave activity flux (TNF) [64] and investigate theenergy dispersion e TNF regressions against precipi-tation indexes are shown in Figure 11 Figure 11(a) showsthat for the NCR a wave train propagates eastward orig-inating from the Mediterranean at the midlatitudes passesthrough Central Asia and converges at the Baikal regionwhich is conducive to an intense cyclone there Althoughthe western part of the wave train is not significant at the90 confidence level it suggests moderate linking

Figure 11(b) is for the TPR ere is a noticeable TNFspreading southeast to Central Asia and to the TP from thehigh- latitude and strengthens the South Asian High InFigure 11(c) there is an apparent eastward propagation of aRossby wave over the midlatitudes of Eurasia e per-spective of the quasi-geostrophic stream function and TNFanomaly reveals when the ISR increases there is astrengthened negative anomaly over the Baikal regionleading to a rising trend of rainfall over NC

To further explore the relation between the wave activityflux and diabatic heating over the TP and the IS the TNFresults of the LBM for different forcings are calculated andare shown in Figure 12 In addition to the three forcingsdiscussed above we add a heat forcing over the TP as theTPH experiment but using a positive value set as the TPC

Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)

Figure 8 Steady 500 hPa height (contours units gpm) and 500 hPa wind (vectors units mmiddotsminus1) anomalies generated by COM on (a) day 1(b) day 5 (c) day 10 and (d) day 15

0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)

Figure 9 (a) 200 hPa height (contours units gpm) and (b) 850 hPa wind (vectors units mmiddotsminus1) anomalies generated by COM experimenton day 15


experiment For diabatic heating over India (Figure 12(a))the wave activity flux originates fromNorth Africaen thewave train moves to Central Asia via Europe into thesubtropical jet stream which verifies that ISM heating can

trigger a midlatitude response In the TP heating case(Figure 12(b)) there are two wave sources located in NorthAfrica and Central Asia e wave noticeably spreadsnorthwestward to the west of Central Asia and then is

60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)

Figure 10 (a) Pacific-Japan (PJ) teleconnection patterns in JA from 1979 to 2017 (shadings) (b) JA precipitation (shadings units mmiddotdayminus1)regressed on the corresponding PJ index Red and blue contour lines indicate positive and negative anomalies of (a) 850 hPa relative vorticity(units 10minus6 sminus1) and (b) 500 hPa height (units gpm) generated by COM experiment on day 15 Dark (light) stippling indicates valuessignificantly exceeding the 99 (90) confidence level using Studentrsquos t test the variance fraction explained by EOF1 is denoted at the top-right corner in (a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)

Figure 11e linear regression pattern of the quasi-geostrophic stream function anomaly (QG) (contours units 106m2middotsminus1) and T-N waveactivity flux (TNF) (vectors units m2middotsminus2) at 200 hPa against (a) NCR (b) INR and (c) ISR Dark (light) shadings indicate values sig-nificantly exceeding the 99 (90) confidence level using Studentrsquos t test


divided into two branches One branch spreads southeast-ward and enhances the South Asian High and the otherbranch spreads eastward and dissipates in the Pacific Oceanwhich agrees with observations well [65] Figure 12(c) showsthe results of the TPC experiment Compared with the TPHexperiment the intensity of the TNF decreases considerablye TPCrsquos TNF result is similar to the result shown inFigure 11(b) but has opposite effect which strengthens thecyclone in Baikal region For the combined forcing(Figure 12(d)) it indicates the best agreement with obser-vations Heating over the IS triggers a wave train in favor ofTP cooling and spreads in two directions one is orientedsoutheastward to the TP and the other path is oriented alongthe westerly jet stream to the east which is beneficial to theweakening of the South Asian High and the strengthening ofthe cyclone over the Baikal region us the propagation ofthe Rossby wave is the evidence for the tripole pattern

6 Discussion and Conclusions

We obtain a clear understanding of the relationship betweenthe ISM (ie precipitation over IS) TP diabatic heating (ie

precipitation over southeastern TP) and rainfall over NCe tripole pattern also shows some instability in some yearsand needs to be further explored Moreover the causes of thelow-frequency variability of the atmosphere are diverse[66ndash68] In this study we investigate the effect of tropicalheating anomalies on existing extratropical teleconnectionpatterns However the reliability of the TNF in low latitudesrequires further consideration e fact that the WPSH hasbeen moving northward in recent years [69] also has animpact on the propagation of midlatitude wave trainsAdditionally the Rossby wave train that stretches fromwestern Europe to West Central Asia is also caused by thestrong barotropic instability at the jet stream exit region inthe North Atlantic Ocean [30] erefore further studies arerequired to determine the relationships among the differentresources

Based on 56 years of JA precipitation this study explainsthe IS-TP-NC tripole pattern e ISM and the TP are bothimportant heating sources in Asia and are interactive usthey are considered as one system and the synergy effect ofthe ISM and TP heating is the focus of this study In thisstudy we analyze the mechanism of the formation of thistripole pattern from the perspectives of circulation LBMnumerical experiments and wave propagation According tothe results the formation of the tripole pattern is caused by asynergy effect of diabatic heating over the IS and the TP

e sketch map shown in Figure 13 illustrates themechanism of the tripolar pattern In summer increasedprecipitation over the IS is corresponding to decreasedprecipitation over the southeastern TP ie an enhancedISM and a decrease in southeastern TP thermal forcing andvice versa In the first case there is enhanced convection andeasterlies over the IS e baroclinic structure at low-lati-tudes produces strong upward movement as a result of thestrengthened vertical wind shear Moreover a Gill-typeRossby wave is generated and propagates westward along the

60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)

Figure 12 e QG (contours units 106m2middotsminus1) and TNF (vectors units m2middotsminus2) at 200 hPa for (a) INH (b) TPH (c) TPC and (d) COMexperiments

Figure 13 Schematic diagram showing the mechanism of tripolepattern e letters denote anticyclonic and cyclonic circulationcenters in 200 hPa Black arrow denotes the easterly jet Grey arrowdenotes Kelvin waves Purple arrow denotes PJ pattern e greendashed arrow denotes water vapor transport


abnormal easterlies to North Africa is leads to a diver-gence in the higher troposphere which triggers an externalRossby wave and moves eastward and is maintained byextracting the kinetic energy of the basic zonal flow Inaddition the strengthened ISM is benefit to the divergenceover Central Asia and this would further reinforce the wavetrain e wave train affects the distribution of the circu-lation at the midlatitudes with the PJ pattern induced bystrengthened ISMus there is a cyclonic anomaly over theBaikal region and an anticyclonic anomaly over the NorthPacific Ocean leading to abundant water vapor transportand sufficient upward movement over NC Additionally oneof the wave trains is oriented southeastward to the TPweakening the South Asian High

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

Acknowledgments

is research was jointly supported by the National KeyRampD Program of China (Grant no 2016YFA0600702) theNational Natural Science Foundation of China for KeyProgram (Grant nos 41630426 and 41975083) and the QingLan Project and the Priority Academic Program Develop-ment of the Jiangsu Higher Education Institutions (PAPD)

References

[1] Y Wang ldquoEffects of blocking anticyclones in Eurasia in therainy season (MeiyuBaiu season)rdquo Journal of the Meteoro-logical Society of Japan Ser II vol 70 no 5 pp 929ndash9511992

[2] N Sato andM Takahashi ldquoDynamical processes related to theappearance of quasi-stationary waves on the subtropical jet inthe midsummer northern hemisphererdquo Journal of Climatevol 19 no 8 pp 1531ndash1544 2006

[3] L Pei Z W Yan and H Yang ldquoMultidecadal variability ofdrywet patterns in eastern China and their relationship withthe Pacific decadal oscillation in the last 413 years (in Chi-nese)rdquo Chinese Science Bulletin vol 60 pp 97ndash108 2015 inChinese

[4] Y Ding ldquoSummer monsoon rainfalls in Chinardquo Journal of theMeteorological Society of Japan Ser II vol 70 no 1Bpp 373ndash396 1992

[5] R H Kripalani and A Kulkarni ldquoMonsoon rainfall variationsand teleconnections over south and east Asiardquo InternationalJournal of Climatology vol 21 no 5 pp 603ndash616 2001

[6] R H Zhang ldquoRelations of water vapor transport from Indianmonsoon with that over east Asia and summer rainfall inChinardquo Advances in Atmospheric Sciences vol 18 no 5pp 1005ndash1007 2001

[7] W Zhou W Chen and D X Wang ldquoe implications of ElNintildeo-southern oscillation signal for south China monsoonclimaterdquo Aquatic Ecosystem Health amp Management vol 15no 1 pp 14ndash19 2012

[8] J Zhang C Liu and H Chen ldquoe modulation of Tibetanplateau heating on the multi-scale northernmost marginactivity of East Asia summer monsoon in northern ChinardquoGlobal and Planetary Change vol 161 pp 149ndash161 2018

[9] Q Ding and B Wang ldquoCircumglobal teleconnection in thenorthern hemisphere summerrdquo Journal of Climate vol 18no 17 pp 3483ndash3505 2005

[10] G Chen and R Huang ldquoExcitation mechanisms of theteleconnection patterns affecting the july precipitation innorthwest Chinardquo Journal of Climate vol 25 no 22pp 7834ndash7851 2012

[11] I M Held ldquoStationary and quasi-stationary eddies in theextratropical troposphere theoryrdquo in Large-Scale DynamicalProcesses in the Atmosphere B J Hoskins and R P PearceEds pp 127ndash168 Academic Press London UK 1983

[12] B J Hoskins and T Ambrizzi ldquoRossby wave propagation on arealistic longitudinally varying flowrdquo Journal of the Atmo-spheric Sciences vol 50 no 12 pp 1661ndash1671 1993

[13] T Enomoto ldquoInterannual variability of the Bonin high as-sociated with the propagation of Rossby waves along theAsian jetrdquo Journal of the Meteorological Society of Japanvol 82 no 4 pp 1019ndash1034 2004

[14] Q Ding BWang J MWallace and G Branstator ldquoTropical-extratropical teleconnections in boreal summer observedinterannual variabilityrdquo Journal of Climate vol 24 no 7pp 1878ndash1896 2011

[15] R H Kripalani and S V Singh ldquoLarge scale aspects of India-China summer monsoon rainfallrdquo Advances in AtmosphericSciences vol 10 no 1 pp 71ndash84 1993

[16] B Wang R Wu and K-M Lau ldquoInterannual variability ofthe Asian summer monsoon contrasts between the Indianand the western North Pacific-East Asian monsoonsrdquo Journalof Climate vol 14 no 20 pp 4073ndash4090 2001

[17] Y Y Liu and Y H Ding ldquoAnalysis and numerical simulationof the teleconnection between Indian summer monsoon andprecipitation in North Chinardquo Acta Meteorological Sinicavol 66 no 5 pp 789ndash799 2008 in Chinese

[18] R H Kripalani A Kulkarni and S V Singh ldquoAssociation ofthe Indian summer monsoon with the northern hemispheremid-latitude circulationrdquo International Journal of Climatol-ogy vol 17 no 10 pp 1055ndash1067 1997

[19] R J Greatbatch X Sun and X-Q Yang ldquoImpact of vari-ability in the Indian summer monsoon on the East Asiansummer monsoonrdquo Atmospheric Science Letters vol 14 no 1pp 14ndash19 2013

[20] H Lin and ZWu ldquoIndian summer monsoon influence on theclimate in the North Atlantic-European regionrdquo ClimateDynamics vol 39 no 1-2 pp 303ndash311 2012

[21] T T Han S He H Wang and X Hao ldquoEnhanced influenceof early-spring tropical Indian ocean SST on the followingearly-summer precipitation over Northeast Chinardquo ClimateDynamics vol 51 no 11 pp 4065ndash4076 2018

[22] K-S Yun S-Y Kim K-J Ha and M Watanabe ldquoEffects ofsubseasonal basic state changes on Rossby wave propagationduring northern summerrdquo Journal of Geophysical ResearchAtmospheres vol 116 no D24 2011

[23] J Yang Q Liu Z Liu L Wu and F Huang ldquoBasin mode ofIndian ocean sea surface temperature and northern hemi-sphere circumglobal teleconnectionrdquo Geophysical ResearchLetters vol 36 no 19 2009

[24] G Chen R Huang and L Zhou ldquoBaroclinic instability of thesilk road pattern induced by thermal dampingrdquo Journal of theAtmospheric Sciences vol 70 no 9 pp 2875ndash2893 2013


[25] R Wu ldquoA mid-latitude Asian circulation anomaly pattern inboreal summer and its connection with the Indian and EastAsian summer monsoonsrdquo International Journal of Clima-tology vol 22 no 15 pp 1879ndash1895 2002

[26] M Yanai and C Li ldquoMechanism of heating and the boundarylayer over the Tibetan plateaurdquo Monthly Weather Reviewvol 122 no 2 pp 305ndash323 1994

[27] GWu Y Liu B He Q Bao A Duan and F-F Jin ldquoermalcontrols on the Asian summer monsoonrdquo Scientific Reportsvol 2 no 1 2012

[28] M Lu S Yang Z Li B He S He and Z Wang ldquoPossibleeffect of the Tibetan plateau on the ldquoupstreamrdquo climate overWest Asia North Africa south Europe and the north At-lanticrdquo Climate Dynamics vol 51 no 4 pp 1485ndash1498 2017

[29] J Zhang Q Tang H Chen and S Liu ldquoNorthward shift incirculation system over the Asian mid-latitudes linked to anincreasing heating anomaly over the northern Tibetan plateauduring the past two decadesrdquo International Journal of Cli-matology vol 37 no 2 pp 834ndash848 2016

[30] J Zhang Y Jiang H Chen and Z Wu ldquoDouble-mode ad-justment of Tibetan plateau heating to the summer circum-global teleconnection in the northern hemisphererdquoInternational Journal of Climatology vol 38 no 2 pp 663ndash676 2018

[31] P Chen ldquoermally forced stationary waves in a quasigeo-strophic systemrdquo Journal of the Atmospheric Sciences vol 58no 12 pp 1585ndash1594 2001

[32] G Wu Y Liu Q Zhang et al ldquoe influence of mechanicaland thermal forcing by the Tibetan plateau on Asian climaterdquoJournal of Hydrometeorology vol 8 no 4 pp 770ndash789 2007

[33] X Zhu O Bothe and K Fraedrich ldquoSummer atmosphericbridging between Europe and east Asia influences on droughtand wetness on the Tibetan plateaurdquo Quaternary Interna-tional vol 236 no 1-2 pp 151ndash157 2011

[34] Z S An J E Kutzbach W L Prell and S C PorterldquoEvolution of Asian monsoons and phased uplift of theHimalayandashTibetan plateau since late Miocene timesrdquo Naturevol 411 no 6833 pp 62ndash66 2001

[35] B Wang Q Bao B Hoskins G Wu and Y Liu ldquoTibetanplateau warming and precipitation changes in East AsiardquoGeophysical Research Letters vol 35 no 14 2008

[36] T Yao V Masson-Delmotte J Gao et al ldquoA review of cli-matic controls on δ18O in precipitation over the Tibetanplateau observations and simulationsrdquo Reviews of Geophysicsvol 51 no 4 pp 525ndash548 2013

[37] X Jiang and M Ting ldquoA dipole pattern of summertimerainfall across the Indian subcontinent and the Tibetan pla-teaurdquo Journal of Climate vol 30 no 23 pp 9607ndash9620 2017

[38] L Zhou H Zou S Ma et al ldquoe observed impacts of SouthAsian summer monsoon on the local atmosphere and thenear-surface turbulent heat exchange over the SoutheastTibetrdquo Journal of Geophysical Research vol 120 no 22pp 11509ndash11518 2015

[39] L Feng and T Zhou ldquoWater vapor transport for summerprecipitation over the Tibetan plateau multidata set analysisrdquoJournal of Geophysical Research Atmospheres vol 117no D20 2012

[40] W Dong Y Lin J S Wright et al ldquoSummer rainfall over thesouthwestern Tibetan plateau controlled by deep convectionover the Indian subcontinentrdquo Nature Communicationsvol 7 no 1 p 10925 2016

[41] A Yatagai K Kamiguchi O Arakawa A HamadaN Yasutomi and A Kitoh ldquoAPHRODITE constructing along-term daily gridded precipitation dataset for Asia based

on a dense network of rain gaugesrdquo Bulletin of the AmericanMeteorological Society vol 93 no 9 pp 1401ndash1415 2012

[42] A Becker P Finger AMeyerchristoffer et al ldquoA description ofthe global landndashsurface precipitation data products of the globalprecipitation climatology center with sample applications in-cluding centennial (trend) analysis from 1901ndashpresentrdquo EarthSystem Sciences Data Discussions vol 5 no 2 pp 921ndash9982013

[43] R Adler M Sapiano G Huffman et al ldquoe global pre-cipitation climatology project (GPCP) monthly analysis (newversion 23) and a review of 2017 global precipitationrdquo At-mosphere vol 9 no 4 p 138 2018

[44] D P Dee Uppala S Simmons et al ldquoe ERAndashinterim re-analysis configuration and performance of the data assimi-lation systemrdquo Quarterly Journal of the Royal MeteorologicalSociety vol 137 pp 553ndash559 2011

[45] G R North T L Bell R F Cahalan and F J MoengldquoSampling errors in the estimation of empirical orthogonalfunctionsrdquo Monthly Weather Review vol 110 no 7pp 699ndash706 1982

[46] M Yanai S Esbensen and J-H Chu ldquoDetermination of bulkproperties of tropical cloud clusters from large-scale heat andmoisture budgetsrdquo Journal of the Atmospheric Sciencesvol 30 no 4 pp 611ndash627 1973

[47] M Watanabe and M Kimoto ldquoAtmosphere-ocean thermalcoupling in the North Atlantic a positive feedbackrdquoQuarterlyJournal of the Royal Meteorological Society vol 126 no 570pp 3343ndash3369 2000

[48] M Watanabe and M Kimoto ldquoCorrigendumrdquo QuarterlyJournal of the Royal Meteorological Society vol 127pp 733-734 2001

[49] M Watanabe and F-F Jin ldquoA moist linear baroclinic modelcoupled dynamical-convective response to El Nintildeordquo Journalof Climate vol 16 no 8 pp 1121ndash1139 2003

[50] J Zhang H Chen and S Zhao ldquoA tripole pattern of sum-mertime rainfall and the teleconnections linking northernChina to the Indian subcontinentrdquo Journal of Climate vol 32no 12 pp 3637ndash3653 2019

[51] H J Wang ldquoe instability of the East Asian summermonsoonndashENSO relationsrdquo Advances in Atmospheric Sci-ences vol 19 no 1 pp 1ndash11 2002

[52] Y Ding Y Sun Z Wang Y Zhu and Y Song ldquoInter-decadalvariation of the summer precipitation in China and its as-sociation with decreasing Asian summer monsoon part IIpossible causesrdquo International Journal of Climatology vol 29no 13 pp 1926ndash1944 2009

[53] Y Liu G Wu J Hong et al ldquoRevisiting Asian monsoon for-mation and change associated with Tibetan plateau forcing IIChangerdquo Climate Dynamics vol 39 no 5 pp 1183ndash1195 2012

[54] A E Gill ldquoSome simple solutions for heat-induced tropicalcirculationrdquo Quarterly Journal of the Royal MeteorologicalSociety vol 106 no 449 pp 447ndash462 1980

[55] I M Held R T Pierrehumbert and R L Panetta ldquoDissi-pative destabilization of external Rossby wavesrdquo Journal of theAtmospheric Sciences vol 43 no 4 pp 388ndash396 1986

[56] W A Robinson ldquoTwo applications of potential vorticitythinkingrdquo Journal of the Atmospheric Sciences vol 44 no 11pp 1554ndash1557 1987

[57] K H Cook ldquoGeneration of the African easterly jet and its rolein determining west African precipitationrdquo Journal of Cli-mate vol 12 no 5 pp 1165ndash1184 1999

[58] C orncroft and M Blackburn ldquoMaintenansce of the Af-rican easterly jetrdquo Quarterly Journal of the Royal Meteoro-logical Society vol 125 no 555 pp 763ndash786 1999


[59] G X Wu W Li H Guo H Liu J Xue and Z WangldquoSensible heat driven airndashpump over the Tibetan plateau andits impacts on the Asian summer monsoon (in Chinese)rdquo inCollection in Memory of Zhao Jiuzhang Y Duzheng Edpp 116ndash126 Chinese Science Press Beijing China 1997

[60] H Lin ldquoGlobal extratropical response to diabatic heatingvariability of the Asian summer monsoonrdquo Journal of theAtmospheric Sciences vol 66 no 9 pp 2697ndash2713 2009

[61] Y Kosaka and H Nakamura ldquoStructure and dynamics of thesummertime Pacific-Japan teleconnection patternrdquo QuarterlyJournal of the Royal Meteorological Society vol 132 no 619pp 2009ndash2030 2006

[62] Y Kosaka and H Nakamura ldquoMechanisms of meridionalteleconnection observed between a summer monsoon systemand a subtropical anticyclone Part I the pacific-Japan pat-ternrdquo Journal of Climate vol 23 no 19 pp 5085ndash5108 2010

[63] Y Kosaka S-P Xie N-C Lau and G A Vecchi ldquoOrigin ofseasonal predictability for summer climate over the north-western Pacificrdquo Proceedings of the National Academy ofSciences vol 110 no 19 pp 7574ndash7579 2013

[64] K Takaya and H Nakamura ldquoA formulation of a phase-independent wave-activity flux for stationary and migratoryquasigeostrophic eddies on a zonally varying basic flowrdquoJournal of the Atmospheric Sciences vol 58 no 6 pp 608ndash627 2001

[65] Q Ding and B Wang ldquoIntraseasonal teleconnection betweenthe summer Eurasian wave train and the Indian monsoonrdquoJournal of Climate vol 20 no 15 pp 3751ndash3767 2007

[66] I M Held S W Lyons and S Nigam ldquoTransients and theextratropical response to El Nintildeordquo Journal of the AtmosphericSciences vol 46 no 1 pp 163ndash174 1989

[67] K L Swanson ldquoStationary wave accumulation and thegeneration of low-frequency variability on zonally varyingflowsrdquo Journal of the Atmospheric Sciences vol 57 no 14pp 2262ndash2280 2000

[68] K L Swanson ldquoOscillatory instabilities to zonally varyingbarotropic flowsrdquo Journal of the Atmospheric Sciences vol 58no 21 pp 3135ndash3147 2001

[69] B Zhou Y Xu and Y Shi ldquoPresent and future connection ofAsian-Pacific oscillation to large-scale atmospheric circula-tions and East Asian rainfall results of CMIP5rdquo ClimateDynamics vol 50 no 1-2 pp 17ndash29 2017


(ISM) and suggested that increased precipitation over theIndian subcontinent (IS) played an important role in theboreal atmosphere during summer

Many previous publications have focused on the rela-tionship between precipitation over NC and the ISMKripalani and Singh [15] noted that the rainfall over NC ishighly related to rainfall over India and suggested to take thesubtropical ridge over the Indian region as an importantpredictor over India as well as over NC Wang et al [16] andDing and Wang [9] commented that the rainfall showssynchronous anomalies over the IS and NC during summerLiu and Ding [17] also utilized the model to simulate theprecipitation teleconnection between India and NorthChina Various studies documented that the ISM affected thesummer climate in East Asia through a midlatitude wavetrain along the East Asian upper tropospheric westerly jetstream causing differences in atmospheric circulation andwater vapor transport [18 19] e results further revealedthat an enhanced ISM could generate anomalous cycloniccirculation over the Mediterranean Sea in the upper layer[20 21] and stimulated a continuous downstream air flowie a silk road pattern [22] with a barotropic anticyclonicanomaly over East Asia leading to more water vapor beingtransported northward along the western periphery of theWPSH [23] However the position and intensity of the ISMwhich lead to precipitation over NC exhibit large vari-abilities in addition to land-sea thermal contrasts and areaffected by atmospheric internal dynamic processes [24] andEl Nintildeo-Southern Oscillations (ENSO) [25] e thermalforcing of the Tibetan Plateau (TP) also plays a decisive rolethrough air pumping [26ndash28] Moreover the TP also has aconsiderable influence on the boreal circulation and pre-cipitation as a significant surface and atmospheric heatingsource in summer [29 30] which therefore is alsoconsidered

e change in TP diabatic heating especially latentheating released by rainfall in summer has a profoundinfluence on the seasonal circulation and the interannualchanges of the Northern Hemisphere [31] and it has con-siderable influence on the precipitation over NC during thesummer time Observational studies have shown that in-creased TP heating can intensify East Asian summermonsoons which contribute to the upward trend of mon-soon rainfall over NC [32 33] Heating on the TP will triggertwo waves One wave travels downstream along the westerlyjet stream and the other wave spreads along the low-levelsouthwesterly monsoon flow to the South China Sea [34]e west one results in an anticyclone over NC leading toless precipitation there [35]

Despite the effect of TP thermal forcing on the ISM theISM can also affect summer rainfall over the TP over a widerange of time scales [36 37] which is modulated by at-mospheric processes over the midlatitudes [38] and in-coming water vapor transport [39 40] further affecting thethermal condition of the TP

Prior to the current study of precipitation over NC moststudies have typically involved only one single influencefactor because it is difficult to identify the main influencingfactors which vary but may not be considered Because of

the interactive relationship between the TP thermal forcingand the ISM it is reasonable to regard both as one phe-nomenon or to assume that they are one system Addi-tionally the investigations on the role of tropical heatinghave been limited to only revealing the correlation thus themechanism is unclear

Based on the above discussions the objectives of thisstudy were to determine the precipitation distributionpattern during summer investigate the effect of the ISM andTP heating on the precipitation over NC and utilize a modelto understand the mechanism is paper focuses on thevariability of the midlatitude wave train which will help tointerpret extratropical responses to the tropical heatinganomalies in Asia Amore practical motivation for this studyis that the precipitation over NC can be fully and accuratelypredicted

e structure of this paper is as follows Section 2 de-scribes the data and methods Section 3 shows the tripolepattern distribution and the related circulation In Section 4we describe the model experiments performed to obtain thecirculation response to different forcing Section 5 presentsthe wave activity flux to analyze the propagation of the waveBrief conclusions and discussions are provided in Section 6

2 Materials and Methods

In this study we focused on the concentration period (July-August JA) of summer rainfall when the precipitation modeis most typical and a wave-like pattern is also often observedover Eurasia

e following datasets were used in this study (1) edaily precipitation data (APHRO) were derived from theAsian Precipitation -Highly-Resolved Observational DataIntegration towards Evaluation of the Water Resources(APHRODITE) e subset of APHRO covered MonsoonArea (60degN-150degN15degS-55degN) APHRO_MA_V1101 wasused e product includes daily rainfall from 1951 to 2007with a spatial resolution of 025deg times 025deg e APHRO rainfallshows fair applicability in the TP and surrounding areasbecause of its high resolution and improvement in inter-polation [41] To verify the results the global rainfall datasetthe Global Precipitation Climatology Centre monthly(GPCC) mean rainfall data was derived from the NationalOceanic and Atmosphere Administration (NOAA) at aresolution of 10deg times10deg and the data were chosen for theperiod of 1901ndash2013 (httpwwwesrlnoaagovpsd [42])Monthly mean rainfall from the Global Rainfall ClimatologyProject (GPCP) analysis dataset version 23 from 1979 to2017 (httpgpcpumdedu [43]) was used (2) e Eu-ropean Centre for Medium-Range Weather Forecasts(ECMWF) Interim Re-Analysis monthly atmospheric re-analysis data included geopotential height and zonal andmeridional winds at 200 hPa 500 hPa and 850 hPa on a15deg times15deg grid for 1979ndash2017 which were obtained from theECMWF (httpappsecmwfintdatasets [44])

e main statistical tools used in this study includedempirical orthogonal function (EOF) analysis correlationanalysis and regression analysis Linear trends were re-moved from all the data before the regression and




Q1 Cp

zT

zt+ V

rarrlowastnablaT +

p

p01113888 1113889

κ

ωzθzp

1113890 1113891

Q2 minusL

Cp

zq


zq

zp1113890 1113891

(1)












50N

40N

30N

20N

IS

TP

NC

141

80E 100E 120E


(a)

30201000

ndash10ndash20

1980 1990 2000 2010

(b)


120E

50N

40N

30N

20N 4

0

0

0

0

2

ndash2

(c)

30201000


1980 1990 2000 2010

TPRNCRISR

(d)





1

0 30E 60E 90E 120E 150E 1800

20N

40N

60N

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

CA

CA

1


(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180


15

(c)


0

30N

60N

A CA

C A

1

0 30E 60E 90E 120E 150E 180


(a)

0

30N

60N

C C

1

0 30E 60E 90E 120E 150E 180


(b)

0

30N

60N

A CA

CA

1

0 30E 60E 90E 120E 150E 180


(c)








0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(a)

0

30N

60NA

3

C

C

C

0 30E 60E 90E 120E 150E 180

(b)

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(c)







0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)






60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References












































































Q1 Cp

zT

zt+ V

rarrlowastnablaT +

p

p01113888 1113889

κ

ωzθzp

1113890 1113891

Q2 minusL

Cp

zq


zq

zp1113890 1113891

(1)












50N

40N

30N

20N

IS

TP

NC

141

80E 100E 120E


(a)

30201000

ndash10ndash20

1980 1990 2000 2010

(b)


120E

50N

40N

30N

20N 4

0

0

0

0

2

ndash2

(c)

30201000


1980 1990 2000 2010

TPRNCRISR

(d)





1

0 30E 60E 90E 120E 150E 1800

20N

40N

60N

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

CA

CA

1


(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180


15

(c)


0

30N

60N

A CA

C A

1

0 30E 60E 90E 120E 150E 180


(a)

0

30N

60N

C C

1

0 30E 60E 90E 120E 150E 180


(b)

0

30N

60N

A CA

CA

1

0 30E 60E 90E 120E 150E 180


(c)








0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(a)

0

30N

60NA

3

C

C

C

0 30E 60E 90E 120E 150E 180

(b)

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(c)







0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)






60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References













































































50N

40N

30N

20N

IS

TP

NC

141

80E 100E 120E


(a)

30201000

ndash10ndash20

1980 1990 2000 2010

(b)


120E

50N

40N

30N

20N 4

0

0

0

0

2

ndash2

(c)

30201000


1980 1990 2000 2010

TPRNCRISR

(d)





1

0 30E 60E 90E 120E 150E 1800

20N

40N

60N

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

CA

CA

1


(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180


15

(c)


0

30N

60N

A CA

C A

1

0 30E 60E 90E 120E 150E 180


(a)

0

30N

60N

C C

1

0 30E 60E 90E 120E 150E 180


(b)

0

30N

60N

A CA

CA

1

0 30E 60E 90E 120E 150E 180


(c)








0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(a)

0

30N

60NA

3

C

C

C

0 30E 60E 90E 120E 150E 180

(b)

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(c)







0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)






60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References












































































1

0 30E 60E 90E 120E 150E 1800

20N

40N

60N

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

CA

CA

1


(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180


15

(c)


0

30N

60N

A CA

C A

1

0 30E 60E 90E 120E 150E 180


(a)

0

30N

60N

C C

1

0 30E 60E 90E 120E 150E 180


(b)

0

30N

60N

A CA

CA

1

0 30E 60E 90E 120E 150E 180


(c)








0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(a)

0

30N

60NA

3

C

C

C

0 30E 60E 90E 120E 150E 180

(b)

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(c)







0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)






60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References















































































0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(a)

0

30N

60NA

3

C

C

C

0 30E 60E 90E 120E 150E 180

(b)

0

30N

60NA

3

C

C

0 30E 60E 90E 120E 150E 180

(c)







0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)






60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References














































































0 2 4 6 8 10 12 14

Kday

600

500

400

300

200

100Le

vel (

hPa)

Q1Q2

(a)

ndash10 ndash05 00 05 10 15 20

Kday

600

500

400

300

200

100

Leve

l (hP

a)

Q1Q2

(b)

ndash20 ndash10 00 10 20 30 40 50

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(c)

ndash10 ndash05 00 05 10 15 20

Kday

1000

800

600

400

200

0

Leve

l (hP

a)

Q1Q2

(d)






60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References













































































60N

40N

20N

60E 90E 120E

Kday

(a)

00

02

04

06

08

1000 02 04 06 08 10 12

Kday

(b)

00

02

04

06

08


Kday

(c)







0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References














































































0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

816

16

24

8

8(a)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

8

5

(b)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(c)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash20

ndash20

ndash40

(d)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

ndash8ndash8

8

5

(e)

0 30E 60E 90E 120E 150E 180

0

30N

60N

Day15

2

(f )














Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References





















































































Day 1

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(a)

Day 5

0

30N

60N5

0 30E 60E 90E 120E 150E 180

(b)

Day 10

0

30N

60N5

10

ndash4

ndash4

ndash4

0 30E 60E 90E 120E 150E 180

(c)

Day 15

0

30N

60N10

ndash4

ndash4

ndash4

5

0 30E 60E 90E 120E 150E 180

(d)


0

30N

30S

60S

60N

0

8

8 ndash8

8

ndash24

ndash24ndash32

30E 60E 90E 120E 150E 180

Day15

(a)

0

30N

60N

0 30E 60E 90E 120E 150E 180

Day15

2

(b)





60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References












































































60N

30N

0100E 120E 140E 160E


143

00

0

0

0

1

ndash1ndash1

0

2

0

0

ndash1ndash4

ndash2ndash2

ndash2

0

0

0 1

0

0

0

0

(a)

60N

30N

0120E 140E 160E100E

ndash008 ndash004 0 004 0082

2

20

0 ndash2

4

6

640

2

ndash2

ndash4

2

000

000ndash004

000

000

000

(b)


60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(a)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(b)

60N

40N

20N

00 30E 60E 90E 120E 150E 180

3

(c)









60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References
















































































60N

40N

20N

30E 60E 90E 120E 150E

1

180

(a)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(b)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(c)

60N

40N

20N

1

30E 60E 90E 120E 150E 180

(d)





Data Availability




Acknowledgments


References











































































Data Availability




Acknowledgments


References










































































synergy effects of the indian summer monsoon and...

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