shallow orographic heavy rainfall in the asian monsoon region...
TRANSCRIPT
Shallow orographic heavy rainfall in the Asian monsoon region observed by TRMM PR
Shoichi Shige1 & Christian D. Kummerow2 1Graduate School of Science, Kyoto University
2Dept. of Atmospheric Science, Colorado State University
Background
APHRODITE
PR GSMaP GPROF
GSMaP-PR GPROF−PR
India [Shige et al. 2014] June–August 2007
Precipitation Radar PR
TRMM Microwave Imager TMI
mature stage cumulus stage dissipating stage
Wallace & Hobbs (2006) [Adapted from Byers and Braham (1949)]
MWR rainfall algorithms assume that heavy rainfall results from deep clouds.
Background (Continued)
Weak Scattering ↓
Light Rainfall
Strong Scattering ↓
Heavy Rainfall
Background (Continued)
mature stage cumulus stage
Wallace & Hobbs (2006) [Adapted from Byers and Braham (1949)]
However, heavy rainfall can be caused by shallow orographic convection in moist Asian monsoon regions.
mature stage Obs. TB
Est. Rain
Underestimate
Orographic Original
LUT@85 GHz
Background
APHRODITE
PR GSMaP
GSMaP-PR
June–August 2007 India [Shige et al. 2014]
Land Ocean
yhv
xhu
DtDhw
¶¶
+¶¶
==
Orographically Forced Upward Motion
Background
APHRODITE
PR GSMaP GSMaP(revised)
GSMaP-PR GSMaP(revised)−PR
India [Shige et al. 2014] June–August 2007
What environmental thermodynamic parameters constrain the depth of orographic rain clouds?
??? ???
Mexico
Cardamom
Bilauktaung
Arakan Yoma
Annam Cordillera
Phillipines
Western Ghats
Murakami & Matsumoto (1994, JMSJ)
Mexico
Cardamom
Bilauktaung
Arakan Yoma
Annam Cordillera
Phillipines
Western Ghats
I II V VI
Logtitude-height sections of the 5-year unconditional mean Q1-QR for the June-August season
18oN
Fig. 2: Schematic of target region and upstream region.
ERA-Interim 0.75o
Low-level upstream
region
Target region
hDtDhw Ñ×== Horo V
z = 4.5 km
z = 2.5 km
TRMM PR: 0.05o ERA-Interim: 0.75o
SRTM30: the original 1-km resolution data averaged within the horizontal length scale of 50km
Mid-level upstream
region
z = 7.5 km
The 7-yr conditional mean Q1 − QR and RH profiles stratified with dp/dt at 500 hPa averaged over the ocean, associated with (a) all rain, for all rain averaged over the grids with SST of
28.0°–29.0°C. (Takayabu et al. 2010 JC)
Q1 − QR RH
DRY MOIST Ocean
Fig. 6: Precipitation profiles with heavy near-surface rain rates (10 mm h-1 < R ≤ 40 mm h-1) and upward motion (woro > 0 m s-1) as a function of RHlow. Contours indicate values of the confidence interval for the mean at the 95 % level with Student’s t test.
-0.91 -0.71 -0.80
-0.75 -0.97 -0.19
RHlow Correlation coefficients with PTH(1 mm h-1)
Fig. 6: Precipitation profiles with heavy near-surface rain rates (10 mm h-1 < R ≤ 40 mm h-1) and upward motion (woro > 0 m s-1) as a function of RHmid. Contours indicate values of the confidence interval for the mean at the 95 % level with Student’s t test.
-0.94 -0.68 -0.76
-0.77 -0.39 -0.68
RHmid Correlation coefficients with PTH(1 mm h-1)
MOIST DRY
What determines deep or shallow?
DRY MOIST Ocean
Mountain
-0.90 -0.90 -0.61
-0.83 -0.78 -0.92
Fig. 10: As in Fig. 3 but for precipitation profiles with near-surface rain rates of 10 mm h-1 < R ≤ 40 mm h-1 and upward motion (woro > 0 m s-1) as a function of dT/dzlow.
dT/dzlow Correlation coefficients with PTH(1 mm h-1)
Fig. 9: As in Fig. 3 but for precipitation profiles with heavy near-surface rain rates (10 mm h-1 < R ≤ 40 mm h-1) and upward motion (woro > 0 m s-1) as a function of dT/dzmid.
-0.95 -0.71 -0.82
-0.83 -0.97 -0.89
dT/dzmid Correlation coefficients with PTH(1 mm h-1)
I II V VI
Fig. 13: Jun-Aug climatology (2004-2008) of dT/dzmid with horizontal winds at z=5.5 km (top) and function of dT/dzlow with horizontal winds at z=2.5 km (bottom) from ERA Interim.
dT/dzmid dT/dzlow
Low-level or mid-level static stability determines precipitation depths?
Summary • Heavy rainfall can be caused by shallow convection over mountain
ranges of the Asian monsoon regions, which differs from the assumptions of MWR algorithms.
• Depth of heavy orographic rainfall decreases with RH in opposition to what has been observed for oceanic convection.
• Depth of heavy orographic rainfall also decreases with the low-level and mid-level static stability.
• Mid-level static stability, which inhibit cloud growth and promotes cloud detrainment, is inferred to be a key parameter determining precipitation depths.
• Low-level static stability, however, might be more effective to improve microwave radiometer rainfall algorithms, because of a result of shallow convection and their strong links.
Fig. 11 Comparison of correlation coefficients between candidate thermodynamic quantities and precipitation top heights
Fig. 8: Two dimensional histogram of grid with heavy rain rates (10 mm h-1 < R ≤ 40 mm h-1) as function of woro and RHmid for Western Ghats, Arakan Yoma, and Bilauktaung.
Fig. 8: Two dimensional histogram of grid with heavy rain rates (10 mm h-1 < R ≤ 40 mm h-1) as function of woro and RHmid for Western Ghats, Arakan Yoma, and Bilauktaung.
Mexico
Cardamom
Bilauktaung
Arakan Yoma
Annam Cordillera
Phillipines
Western Ghats
I II V VI III IV I V
I II
III IV I V
V VI
I: Western Ghats II: Arakan Yoma III: Bilauktaung IV: Cardamom V: Annam Cordillera VI: Phillipines
MOIST STABLE
DRY UNSTABLE
What determines deep or shallow?
DRY MOIST Ocean
Mountain
Kato et al. (2007, JMSJ)
The relatively stable atmospheric condition around the Japan Islands, found when the LNB appears at the MP, is mainly caused by the advection of a middle-level air that is warmed through convective activities over upstream regions, especially the China Continent.
Murakami & Matsumoto (1994, JMSJ)
Kummar et al. (2014, CD)
Jun-Jul
Aug-Sep
Deeper clouds appear more frequently over the Myanmar coast, while shallower clouds over the Western Ghats.
Mexico
Cardamom
Bilauktaung
Arakan Yoma
Annam Cordillera
Phillipines
Western Ghats
Look-up table: Relationship between Tbs and rain rates
Obs. TB
Est. Rain
Underestimate
Ice
Water
Ice
Water
Original
Orographic Typhoon
Namtheun
Orographic Original
LUT@85 GHz
Shige et al. (2013, JAMC)
Retrieval
Original LUTs
Orographic LUTs
Yes No
GANAL
w > 0.1 Q > 0.5×10-6
SRTM30
Retrieval
Orographic/Non-Orographic Rainfall Classification Scheme
Land Ocean
yhv
xhu
DtDhw
¶¶
+¶¶
==
( ) ( )÷÷ø
öççè
æ¶
¶+
¶¶
-=yvq
xuqQ
Convergence of Surface Moisture Flux
Orographically Forced Upward Motion
Shige et al. (2013, JAMC) Taniguchi et al. (2013, JH)
Typhoon Namtheun (2004) over Japan (Kubota et al. 2009, JMSJ)
PR
GSMaP
GPROF PR PTH (km)
TMI PCT85 Radar-AMeDaS
Mexico
Cardamom
Bilauktaung
Arakan Yoma
Annam Cordillera
Phillipines
Western Ghats
Wang & LinHo (2002, JC)
Fig. 1: Location of mesoscale mountain ranges (Western Ghats, Arakan Yoma, Bilauktaung, Cardamom, Annam Cordillera and the Phillipines) of the South Asian monsoon region (Fig 1a) and Mexico for comparison (Fig. 1b).
Baja California
Cardamom
Bilauktaung
Arakan Yoma
Annam Cordillera
the Phillipines
Western Ghats
Fig. 11
-0.72
-0.84 -0.85
-0.69
-0.89
-0.78
Typhoon Morakot (2009) over Taiwan: Taniguchi et al. (2013, JHM)
hDtDhw Ñ×== Horo V
Background:
(a) (b)
(c) (d)
PR SRTM30
TRMM satellite overpass of Typhoon Morakot over Taiwan (Taniguchi et al. 2013, JHM)
Precipitation Radar PR
TRMM Microwave Imager TMI
TRMM (Nov 1997~)
http://www.boston.com/bigpicture/2009/08/typhoon_morakot.html
Background:
(a) (b)
(c) (d)
PR
GSMaP (TMI) GPROF (TMI)
SRTM30
TRMM satellite overpass of Typhoon Morakot over Taiwan (Taniguchi et al. 2013, JHM)
Precipitation Radar PR
TRMM Microwave Imager TMI
TRMM (Nov 1997~)
Typhoon Morakot (2009) over Taiwan Taniguchi et al. (2013, JHM)
Applied orographic profile
PR _ Near Surface Rain
SRTM30_Topography
GSMaP_TMI_Surface Rain (orig.) GSMaP_TMI _Surface Rain
Orographic Forced Lifting Convergence of Surface Moisture Flux
w > 0.1 (ms-1) Q > 0.5 ×10-6 (s-1)