The variability of the Asian summer monsoon in warmer climate

Ding Yihui*

(National Climate Center, CMA)

*Contributers: Wang Zunya, Sun Ying,Liu Yunyun, Liu Yanju, Song Yafang, Zhang Jin

Outline

1. The variability of Asian summer monsoon under global warming in last 100-years

2. Future change in Asian summer monsoon in a warmer world in next 100 years

3. Discussions and conclusions

1. The variability of Asian summer monsoon under global warming in

last 100-years

Fig.1. The vertically integrated moisture flux transport (surface to 300hPa )averaged for summer (JJA: June, July and August) of 1948-2006(Unit ： kg.m-1.s-1）

Climatology of the Asian summer monsoon

Fig.2. The vertically integrated field of divergence of moisture transport for JJA of 1948-2006. Negative (positive) regions denotes the convergence (divergence) of moisture （ Unit ： 10-5 kg.m-2.s-1)

Fig.3. Climatological mean (1979-2006) summer precipitation pattern ( Unit:mm.d-1)

27.00

23.49

37.71

116.33

8.79

94.72

1.16

49.6391.24

97.58

32.11

267.35

202.54

(-5.82)

(+78.81)

(+70.42)162.21193.06

29.19

120.21

786.60

79.52

834.39

143.47

455.54 111.64

124.59

405.21

267.87

544.98

202.29

28.66

53.39

(+30.61)

(+341.80)

202.46

(+201.14) (+519.28)(+85.23) (+329.27)

(-892.19)SIO

AS BOB SCS

SC

YHRB

NC

NWNP

SWNP

NEC

27.00

23.49

37.71

116.33

8.79

94.72

1.16

49.6391.24

97.58

32.11

267.35

202.54

(-5.82)

(+78.81)

(+70.42)162.21193.06

29.19

120.21

786.60

79.52

834.39

143.47

455.54 111.64

124.59

405.21

267.87

544.98

202.29

28.66

53.39

(+30.61)

(+341.80)

202.46

(+201.14) (+519.28)(+85.23) (+329.27)

(-892.19)SIO

AS BOB SCS

SC

YHRB

NC

NWNP

SWNP

NEC

27.00

23.49

37.71

116.33

8.79

94.72

1.16

49.6391.24

97.58

32.11

267.35

202.54

(-5.82)

(+78.81)

(+70.42)162.21193.06

29.19

120.21

786.60

79.52

834.39

143.47

455.54 111.64

124.59

405.21

267.87

544.98

202.29

28.66

53.39

(+30.61)

(+341.80)

202.46

(+201.14) (+519.28)(+85.23) (+329.27)

(-892.19)SIO

AS BOB SCS

SC

YHRB

NC

NWNP

SWNP

NEC

Fig.4. Schematic maps of the climatological mean moisture budgets of the Asian-Pacific summer monsoon region in summer (JJA) (Units:106kg/s). The shaded area refers to the Tibetan Plateau. The positive and negative values represent net moisture influx and efflux, respectively. SIO: South Indian Ocean(30S°-0°N, 40°E-120°E); AS: Arabian Sea(0°-22.5°N, 40°E-80°E); BOB: Bay of Bengal (0°-22.5°N , 80°E-100°E); SCS: South China Sea(0°-22.5°N , 100°E-120°E) ; SC: South China (22.5°N-27°N, 100°E-120°E); YHRB: Yangtze–Huaihe River Valleys(27°N-35°N, 100°E-120°E); NC: North China(35°N-42°N,100°E-120°E); NEC: Northeast China(42°N-54°N ,120°E-135°E); NWNP: northwestern part of North Pacific (22.5°N-45°N , 120°E-160°E); SWNP: southwestern part of North Pacific(0°-22.5N°, 120°E-160°E).(Liu, et al.,2009)

- 1

- 0. 5

0

0. 5

1

1. 5

2

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

year

OBSWG OBSt OBSm21

气温

距平

( C )

年

年

气温

距平

(K)

观测近百余年北半球（上图， Latif 等， 2009 ）和中国（下图，根据龚道溢，王绍武， 2009 计算绘制）年平均气温距平变化（图中黑线是年平均距平，红线是线性趋势，兰线是 21 年滑动平均）

Time series of observed mean surface temperature change for last 100 years Top panel: NH; bottom panel: China. Red: trends , blue:21-yr running average.

Correlation patterns of Asian-Pacific summer (JJA) monsoon

亚洲 - 太平洋季风降水的相关分布

西北太平洋关键区 6~8 月降水与亚洲 - 太平洋季风区降水的相关

季风子系统的遥相关（季节内变率的整体性） 夏季风爆发初期， ISM 通过“南支”遥相关型影响长江流域梅雨； 夏季风盛行期间， ISM 通过“北支”遥相关型影响华北地区降水； WNPSM 主要通过经 30~60 天滤波的 CISO 影响中国夏季降水。

+ + +

-

- + +

+ +

+

-

+

Teleconnection modes of various components of Asian summer system: holistic correlation for ISO

Fig.5. Long-term variation of the East summer monsoon index for 1870-2003 (based on Guo’s monsoon index). Positive(negative)values denote stronger (weaker)summer monsoon than normal. (IPCC, 2007)

Weakening of the Asian summer monsoon and superposed inter-annual and inter-decadal variability .

Inter-decadal variability for all India precipitation 12-18,30-40 and 60-80-yr oscillation

(Goswami,2005)年代际变率： 12-18 年， 30-40 年， 60 与 80 年

-30

-15

0

15

30

-30

-15

0

15

30

1900 1920 1940 1960 1980 2000

-40

0

40

80-30

-15

0

15

30

a

b

c

d

降水距平百分比 /%

Long–tem of anomalous precipitation in Asian-African monsoon regions

西非 West Africa（ Trenberth, et al. 2007）

东非 East Africa （ Trenberth, et al. 2007）

南亚 South Africa（ Trenberth, et al. 2007）

中国华北（ 71个站序列）North China

Ren and Feng (2009)1880-2008 年亚非季风区降水量异常

近 50 年来，西部地区降水约增加 15 ％— 50 ％；东部地区频繁出现“南涝北旱”，华南地区降水约增加 5 ％— 10 ％，而华北和东北大部分地区约减少 10 ％— 30 ％。 （图：

1958-2007 年我国年降水量变化幅度）

（单位：%

/10

年）

我国降水分布发生了明显变化我国降水分布发生了明显变化Significant change in summer precipitation pattern in Significant change in summer precipitation pattern in

China (1958-2007) unit:%/10yrsChina (1958-2007) unit:%/10yrs

（中国气象局气候变化中心）

8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0

2 0

3 0

4 0

5 0

1979-2008 年和 1951-1978 年年平均干旱日数之差

（单位：天）

Difference in drought days between 1979-2008 and 1951-1978

（第二次国家气候变化评估报告初稿， 2009）

近 50 年来中国大陆极端强降水日数的变化趋势（实心和虚心圆分别代表增加和下降趋势，按半径大小分别为每 10 年变化 7.5% 以上， 7.5% ～ 2.5% ，小于 2.5% ，显著变化的地区标有叉号）

Numbers of days of heavy rainfall

Vulnerability of fresh water resources in the context of global climate change (high stress region in North China)

IPCC ， 2007

气候变化下，全球现代淡水资源的脆弱性和他们的管理

华北

(a) (b)

(c) (d)

123 年（ 1880 － 2003 ）中国东部分区降水的变化

Long –term (123yr)variation of summer precipitation in North China (a), Yangtze River basin (b), South China (c) and Meiyu

season

长江

华南 梅雨季

Period (years)

Variance (σ2

)

Period (years)

Variance (σ2

)

Period (years)

Variance (σ2

)

Period (years)

Variance (σ2

)

(a) (b)

(c) (d)

小波分析功率谱： 30-40 年与 80 年周期趋势变化分析： 1978 和 1992 是两个突变点

Spectrum power of wavelet analysis:30-40-yr and 60-80-yr oscillations

华北

(c) (d)

长江

华南 梅雨季

中国东部不同分区夏季降水的主要周期Major periods of summer precipitation in different

subregions of East China

subdivision分区

A 时段（ 123年）

B时段（ 54年）

华南 South China 4, 14*, 30*, 80* 2*, 7, 30*

长江中下游 Yangtze 2*, 7*, 20*, 40* 2*, 7,14, 40*

华北 North China3, 9, 18*, 40*,

803*, 9, 18

长江中下游 5 站 (121 年 )

Meiyu Season2, 7, 12, 40*,

80*2, 7*, 12, 40*

*代表超过 50%信度

中国东部三个地区夏季降水的突变点检验Detection of abrupt change points for different subregions

in East China

Methods方法

South China华南

Yangte长江中下游

North China华北

Meiyu梅雨期长江中下

游 5 站

Running Test 1980, 1992 1978 1965, 1979 1978

Yamamoto et al., (1986)

1980, 1992 1979 1964, 1980 1980

Mann-Kendall (1945; 1975)

1993 1982 1975 1978

所有的突变点都超过 95%的信度

1950 1960 1970 1980 1990 2000 2010Y e ar

-10

-5

0

5

10

15

Tem

pora

l am

plit

ude

1950 1960 1970 1980 1990 2000 2010Y ea r

-15

-10

-5

0

5

10

15

Tem

pora

l am

plit

ude

(a)(b)

(c)(d)

中国夏季降水的 EOF 分析（ 1951-2004 ）

EOF modes of summer precipitation (JJA) for 1951-2004

(a)(c): EOF1 ； (b)(d): EOF2

空间分布 时间系数

1950 1965 1980 1995 2010Y ea r

-40

-20

0

20

40

60

Tem

pora

l am

plit

ude

夏季风水汽输送向量的 EOF分析

下图是时间系数

Leading EOF model of moisture tranport for Asian summer monsoon

-3

-2

-1

0

1

2

3

1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005

b

图 2 1951~2005年夏季 850hPa风场的 EOF分解的第 1 特征向量（ a ）及对应的时间系数（b）

a

1951-1978 1979-1992

1993-2004中国不同时段，夏季降水距平百分比分布的变化。（阴影区是正距平，相对于1971-2000年平均值）

In-decadal shifts of summer monsoon patterns in China shading: positive anomaly

percentage

1951-2004 中国东部 (107.5-130°E) 平均夏季异常降水纬度 - 时间剖面图。单位 : mm

Latitude-time cross-section of summer precipitation departure(107.5-130°E)

850 hPa 平均经向风纬度时间剖面图 （ unit: ms-1 ）。阴影区是异常南风。 Latitude-time cross-section of 850hpa V-component

departures, shading: South wind

1955-2004 异常夏季水汽输送 (a) 和水汽汇 (Q2) (b) 纬度 - 时间剖面图。（地面到 300hPa 输送总量）。单位 : Kgm-1g-1 (a) 和 10-5Kgm-1s-1 (b).

Cross-sections of anomalous moisture (a) transport and divergence (Q2) (b) for East China

(a) (b)

a

C

A

-3

-2

-1

0

1

2

3

1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005

b

c

1951~2005年夏季 850hPa风场的 EOF分解的第 2特征向量（ a）、时间系数（ b）及时间系数的最大熵谱曲线（ c）

Interannual Variability: TBO and 4-7-yr oscillations

850hPa wind EOF2 Time coefficient

a

-3

-2

-1

0

1

2

1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001

-3

-2

-1

0

1

2

3

4

1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001

d

b

c

d

1951~2005 年夏季海平面气压场 EOF 分解的第 1 和 2 特征向量（ a 、 c ）对应的时间系数（ b 、 d ）

EOF fields of (a)EOF1 (c) EOF2 and corresponding time coefficients (b)EOF 1,(d)EOF2

Sea level pressure

1940 1960 1980 2000

-40

-20

0

20

40

1940 1960 1980 2000

-40

-20

0

20

40

1940 1960 1980 2000

-40

-20

0

20

40

1940 1960 1980 2000

-40

-20

0

20

40

(a) (b)

Time series of the anomalous vertically integrated (from surface to 100hPa) apparent heat source (Q1) averaged for all Tibetan Plateau (75 ～ 105°E ， 27.5~42.5°N ) for summer (a), and spring (b). Solid lines denote 9-yr running mean curves. Unit: Wm-2

a

c

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001

b

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001

d

整层积分的大气热源分布（阴影为负值区）

EOF fields of vertically integrated atmospheric heat source (Q1) (a) EOF1; (b) EOF2 and corresponding

time coefficients; (b) EOF1 ； (d)EOF2

e

d

能是亚洲 -太平洋夏季风系统的一种固有振荡，它与暖洋面上的海气相互作用振荡密切关联。

季风强年海温的季节演变合成图（ a 、前一年冬季； b 、当年春季；c 、当年夏季； d 、当年秋季； e 、当年冬季；虚线方框代表印度洋偶极子关键区和 Nino3.4 区）

a

b

c

d

e

Composite SSTA (Nino 3.4) patterns for strong summer monsoon phase of the TBO cycle

e

a: preceding winter (year 0)b ； spring (year 1)c: summer (year1)d: autumn (year1)e: following winter (year2)Box: IOD and Nino 3.4.

SSTA<0SSTA<0 SSTA>0

850hPa风场

SSTA<0SSTA<0 SSTA>0

850hPa风场

亚洲 - 太平洋夏季风准两年振荡的异常场示意图绿色阴影区代表亚洲 - 太平洋季风区夏季大气热源的正值区；黑色箭头代表

850hPa 环流异常场；灰色阴影区代表异常水汽辐合场；红（蓝）色曲线代表海温异常场

Schematic of the anomalous fields for TBO of the Asian –Pacific forced by ENSO events .

2. Future change in Asian summer monsoon in a warmer

world in next 100 years

模式名称 模式和 CMAP 1979-99 夏季平均

降水的相关

模式和 GPCP 1979-99 夏季平

均降水的相关

模式和中国站点降水资料 1979-99 减去

1958-78 降水变化的相关

分类情况

1 CGCM3.1(T47) 0.51 0.39 -0.52 3类2 CGCM3.1(T63) 0.59 0.49 0.31 3类3 CNRM-CM3 0.84 0.85 -0.45 2类4 CSIRO 0.75 0.76 -0.10 2类5 GFDL-CM2.0 0.83 0.83 0.46 1类6 GFDL-CM2.1 0.82 0.80 -0.22 2类7 GISS-EH 0.33 0.36 -0.50 3类8 GISS-ER 0.40 0.44 -0.60 3类9 FGOALS-g1.0 0.24 0.28 -0.50 3类10 INM-CM3.0 0.76 0.70 0.15 2类11 IPSL-CM4 0.68 0.68 -0.42 3类12 MIROC3.2(hires) 0.80 0.82 0.38 1类13 MIROC3.2(medre

s)0.81 0.76 0.23 1类

14 ECHAM5 0.71 0.60 -0.43 3类15 MRI-CGCM2.3.2 0.60 0.61 0.43 3类16 CCSM3 0.57 0.48 -0.09 3类17 PCM 0.28 0.11 0.46 3类18 UKMO-HadCM3 0.89 0.84 -0.76 2类19 UKMO_hadgem1 0.80 0.73 -0.16 2类

Validations of IPCC model performance

2010-2099 中国东部降水变化百分率 EOF 分析结果EOF analysis of summer precipitation in East China for 2010-2099

Fig.10. Future percentage changes(%) in summer precipitation for East Asia and its three sub-regions (South China, Yangtze River Valley(YRV) and North China), relative to climatological mean of 1980-1999. Projections are based on 19 IPCC AR4 climate models.(Sun and Ding,2009)

2010-2099 中国东部降水时间 - 纬度剖面Latitude-time cross-section of East Asian

summer precipitation for 2010-2099

Fig.12. Future change of the East Asian summer index for next 100 years( based on the definition of monsoon index by Lu and Chan, with estimate of the V-component of wind). (Sun and Ding,2009)

2010-2099 东亚 850hPa 水汽输送变化时间 - 纬度剖面Latitude –time cross-section of 850hpa moisture

transport in East Asia for 2010-2099

Projection of South Asian summer monsoon

The land-sea thermal contrast for June-July-August-September (JJAS) between the TP region(20o-40°N, 60o-100°E) and the tropical Indian Ocean (TIO, 10°S-10°N, 60o-100°E) (see the black boxes in Fig. 1a) was computed for both the upper and lower troposphere using TCupper= Thickness(200-500hPa, TP) – Thickness(200-500hPa, TIO) and TClower = Temperature (near-surface [2m], TP) – Temperature (500-850hPa, TIO). The 500-850hPa temperature over the TIO is used as a proxy of near-surface temperature after height adjustment for comparison with 2m air temperature over the TP, which is 2-5km above the mean sea level. (Sun, Ding and Dai,2010)

Long-term (1979-2000) mean of June-July-August (JJAS) 850hPa winds (arrows, in m s-1) and 200-500hPa thickness anomaly (colors, in geopotential meter [gpm]) relative to the mean of the domain (10°S-45°N, 30°-140°E).

Temporal evolution of (a) JJAS MI (black, in m s-1), TCupper (red, gpm), and TClower(blue, gpm), and (b) JJAS -U200 (black, m s-1) and U850 (green, m s-1) anomalies (relative to1980-1999 mean) averaged over 0°-20°N and 40°-110°E, and TCupper (red, gpm), and TClower (blue, gpm) from 1951 to 2099 based on IPCC AR4 7-model arithmetic mean under observation-based forcing during 1951-2000 and the A1B scenario for 2001-2099. U200 anomalies in (b) were multiplied by -1 to show the weakening of 200hPa easterly winds.

IPCC 7-model averaged (a) time-height cross-section of JJAS temperature departures (K, from 1980-1999 mean) averaged over the TIO during 1951-2099. (b) Latitude-height cross-section of JJAS temperature change (K) from 1980-1999 to 2080-2099averaged between 60°E and 100°E. The topography along 90°E is shown by the black areas.

(c) Longitude-height cross-section of change (K, from 1980-1999 mean) in JJAS meridional temperature gradient (temperature changes averaged from 20o-40°N minus that from10°S-10°N) for 2080-2099. The topography along 35°N is shown by the black areas. (d)Time series of JJAS 200-500hPa thickness anomalies (gpm, from 1980-1999 mean) over theTP (solid line) and TIO (dashed line) during 1951-2099.

3. Discussions and conclusions

(1) In recent three decades, North and Northeast China have suffered from severe and persistent droughts while the Yangtze River basin and South China have undergone much more significant heavy rainfall/floods events. This long-term change in the summer precipitation and associated large-scale monsoon circulation features have been examined by using about 123-yr (1880–2002) records of precipitation in East Asia. One dominating mode of the inter-decadal variability of the summer precipitation in China is the near-80-yr oscillation. Then, on this basis, a possible explanation of this long-term change in relation to significant weakening of the Asian summer monsoon, possibly due to the abrupt increase in the preceding winter and spring snow over the Tibetan Plateau and warming of the sea surface temperature in tropical central and eastern Pacific since about 1978,has been set forward.

But we cannot answer whether the anthropogenic forcing has caused the changes of patterns of rainfall, floods/droughts in China, and East Asian monsoon. Natural fluctuation of climate change can also play an important role. It needs the further studies.

(2) It seems that the major rainfall belts would move northward by about 2040, but unstable. Afterwards, the summer precipitation in North China would increase considerably and stably. Furthermore, this anthropogenically-driven precipitation shift would appear to be consistent with the occurrence of rainfall peak period caused by the natural near-80-yr cycle. But this coincidence will be reliable?

(3)The above analyses show that the differential increases of the upper-tropospheric temperature over the TIO and TP lead to the changed relationship between the SASM intensity and tropospheric thermal contrasts over the SASM regions in a GHG-induced warmer climate. The weakening of the SASM circulation is directly related to the decrease of upper-tropospheric TP-TIO thermal contrast, which in turn is caused by the larger upper-tropospheric warming over the TIO than over the TP. The fact that the SASM weakens as the lower-tropospheric thermal contrast increases in the 21st century implies a smaller role of this thermal contrast in determining the SASM intensity than suggested by previousstudies for the 20th century.

(4) Uncertainty of modeling the enhancement of water vapour in upper troposphere in tropics and subtropics