Ding Yihui , Si Dong,Sun Ying, Wang Zunya,Liu Yunyun

China meteorological Administration, National Climate Center

April 8,2013

Long-term variation of heat sources over the Tibetan Plateau

and its impact on the Asian summer monsoon

Outline

1.Long -term variations of heat sources over

the Tibetan Plateau (TP)

2. Impact of Long-tem variation of heat source

over TP on the Asian summer monsoon

3. Future change in the Asian summer

monsoon and its association with TP heating variation

 

Main driving force of the Asian summer monsoon

It is widely accepted that the development of the Asian summer monsoon (ASM) is induced by large-scale thermal gradients between the Asiatic landmass and neighboring oceans. Many researchers have indicated that the Tibetan Plateau is an important player in the heating processes as an elevated heat source in the middle troposphere.

The Asian summer monsoon system

The Asian summer monsoon is composed by South or Southeast Asian monsoon, Western North Pacific monsoon, and East Asian monsoon . All these systems experience clear alternation of wind directions and wet/dry seasons.

Based on studies over many years, it has been found that many differences exist between the monsoon circulation over India and that over East Asia. This suggests that the structure and main components of the monsoon system over East Asia is likely to be independent of the Indian monsoon system, even though there are some significant interactions.

Long -term variations of heat sources over the Tibetan Plateau (TP)

Computational formula ：

Integrating from surface to 100hPa

H=ρ·cp·CH·U·(Ts-Ta)

Estimates of surface sensible heat

CH =0.0012+0.01/U (Chen and Wong 1984)

2

Long-tem variations of heat source over TP

from surface to 100 hPa

垂直积分的（地面至 100 hPa ）高原地区（ 27.5° ～ 42.5°N ， 75° ～ 105°E ）异常热源（ Q1 ）的时间序列：（ a ）夏季；（ b ）春季。实线为 9 年滑动平均，单位：

W m-2 。、 （引自 Ding et al., 2009 ）

亚洲季风区及其相邻海岸区陆地（ 547 个格点，见右上角小图中的计算区）与海洋（ 668 个格点）（ 20°S ～ 45°N ， 30° ～ 140°E ）热力差异指数（ QLS ）的时间序列。实线为 9 年滑动平均。 （引自 Ding et al., 2009 ）

Land –sea thermal contrast (Thermal difference index QLS)

Time series of the difference between the normalized vertically integrated (from surface to 250 hPa) apparent heat source Q1 (W m-2) averaged over the Tibetan Plateau (70°–100°E, 30°–43°N) and the tropical central and eastern Pacific (180°–120°W, 10°S–10°N) for the (a) spring and (b) summer. The solid lines denote 9-year running mean curves.

Temperature variation of

QLS (1979-2011)

（ a ）南亚夏季风区（ 0° ～ 20°N ， 40° ～ 105°E ） 500 ～ 100 hPa 层平均经向温度梯度∂ ΔH / ∂ y 变化，由异常平均经向厚度梯度代表。（ b ）东亚季风区（沿 30°N ， 110° ～ 140°E ）平均纬向温度梯度，由异常纬向厚度梯度−∂ ΔH / ∂y 代表。单位： 10-2 gpm km−1 。 （引自 Ding et al., 2009 ）

Inter-decadal weakening of meridional temperature gradient for the layer of 500-100hPa In South Asian (top) and Zonal temperature gradient in East Asia (bottom) for JJA

（ a ） 1979 ～ 2011 年高原地区（ 30° ～ 43°N ， 70° ～ 100°E ）春季垂直积分（地表至 250 hPa ）的异常 Q1 时间序列（单位： W m-2 ），实线为 9 年滑动平均；（ b ）同（ a ），但为夏季；（ c ）春季高原地区（同上）和热带中东太平洋（ 10°S ～ 10°N ， 180° ～ 120°W ）垂直积分热源（ Q1 ，单位： Wm–2 ）差值的时间序列；（ d ）同（ c ），但为夏季。实线为 9 年滑动平均。 （引自 Si and Ding., 2012 ）

Temporal variation of heat

source TP and QLS for 1979-

2011

Seasonal mean sensible heat fluxes (W m-2) over the Tibetan Plateau averaged for the 72 station for the (a) winter, (b) spring, and (c) summer. The dashed curve indicates the third-order polynomial fit. The horizontal solid lines indicate averaged values for the period of 1979-2011.

Temporal variation of sensible heat flux over TP

for 1979-2011

0

10

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1948 1954 1960 1966 1972 1978 1984 1990 1996 2002 2008Year

W/m

2

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1948 1954 1960 1966 1972 1978 1984 1990 1996 2002 2008Year

W/m

2

spring

summer

Longer temporal variation of heat sources over TP for 1948-2011

（司东博士提供， 2013 ）

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16

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24

28

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

45

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1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Longer variation of the surface sensible heat flux over TP for 1960-2011

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1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

winter

spring

summer

（司东博士提供， 2013 ）

Changes (2000-2007 mean minus 1984-1999 mean) in surface longwave radiation ratio (%) (surface longwave upward flux / surface longwave downward flux ) in (a) winter, (b) spring, and (c) summer.

Decadal increase in

upward longwave radiation

over TP for 2000-2007

(a) Distribution of the 15 radiosonde stations over the Tibetan Plateau. (b) Spring and (c) summer temperature (°C) over the Tibetan Plateau averaged for the

15 radiosonde stations from 500 hPa to 100 hPa. The horizontal solid lines indicate averaged values for the period of 1999-2011. The Dashed curves indicate the third-order polynomial

fits.

Temperature variations

derived from radiosondes at various levels in TP region

1960 ～ 2004 年青藏高原 50 个站（见左上小图）平均积雪深度指数（ SDI ）时间序列：（ a ）冬季（ 12 ～ 2 月），（ b ）春季（ 3 ～ 4 月），（ c ）春季 EOF 第一模态时间系数，虚线为 9 年滑动平均，单位： cm （引自 Ding et al. 2009 ）；（ d ） 1979 ～2011 年高原 72 站冬季积雪深度，单位： cm d–1 （引自Si and Ding. 2012 ）

Long-term variations

of preceding winter and

spring snow-

depth over TP

1960-2004

1979-2011

2. Impact of Long-tem variation of heat source over TP on the Asian

summer monsoon

Long-term variations

of the monsoon index for 1951-2011

summer

winter

(BCC,2011)

东亚夏季风（上）与南亚夏季风（下）持续年代际偏弱（周兵等， 2013 ）

Long-term variations of the monsoon

index for 1951-2012

Top: EA indexBottom: SA index

Pattern of annual precipitation for 1950-2002

（中国气象局国家气候中心）

西部、华南降水呈增加趋势；华北、东北大部降水呈减少趋势

年降水标准化距平序列与自然数列 1 ， 2 ， 3 ，…， 的相关系数。相关系数正负表示增或减

Monsoon precipitation

Arid-and semi-arid precipitation

Patterns of anomalous precipitation for 1951-1978(top),1979-1992(middle) and 1993-2004 (bottom) for JJA

Latitude-time cross-sections of anomalous precipitation (top) and 850hPa V-component (bottom) for JJA

Decadal change in correlation relationship between TP winter snow and summer precipitation from 1960-2004 to 2000-2011

亚洲夏季风减弱可能原因的概略图。异常强、弱的夏季风条件由（ a ）、（ b ）驱动。阴影区为多雪、高 SSTA 、强大气加热和多雨。粗箭头为夏季风气流。 （引自 Ding et al., 2009 ）

Schematic diagram of inter-decadal

weakening of the Asian summer

monsoon

3. Future change in the Asian summer monsoon and its association with TP heating variation

Latitude-time cross-section of East Asian summer precipitation for 2010-2099

2010-2099 东亚夏季风的纬度时间剖面图

Percentage changes (%) of JJA precipitation (relative to 1980–1999 average) for 2010–2019 (a), 2030–2039 (b) and 2080–2099 (c).

2010-2019 2030-2039

2080-2099

JJA precipitation

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).

未来百年东亚夏季风指数的长期变化

Projection of future variations of Asian summer monsoon based on IPCC AR4 14 coupled models

Changes in monsoon indices for South Asia in the period of 2010-1099 (Webster and Yang ：实线， Wang and Fang ：虚线 )

2010-2099 南亚夏季风指数演变

South Asia

Simulated Sea level pressure for 1980–1999

IPCC 9-model mean June-July-August (JJA) sea level pressure (Pa, shaded area) and 850 hPa winds (m/s, arrows) for 1980–1999 (blank areas in wind

fields represents geographical heights greater than 1500 m).

Trends (K/decade) for 2000–2099 temperatures averaged over TP (black), TIO (red), and NWP (blue) from 850 hPa to 100 hPa. The orange line indicates the trend (K/decade) in near-surface temperature over the TP

Projected trends of mean temperature profiles of TP, TIO, and NWP for 2000-2009

(a)IPCC 9-model mean latitude-height cross-section of JJA temperature changes (K, relative to 1980–1999 average) along the longitude belt (i.e.60°–100°E average) over the TP and TIO for 2080–2099. (b) Same as (a), but for the longitude-height cross-

section along the latitude belt (i.e., 20°–40°N average) over the TP and NWP.

Latitude –height cross -section of temperature change along TP-TIO and TP-NWP for 2080-2099

IPCC AR4 9 个耦合模式平均的 2080 ～ 2099 年对 TP 与 TIO 所在纬度带的经向热力差异变化高度—经度剖面图。 （即 20°N ～ 40°N 减 10°S ～ 10°N 平均的变化，相对于 1980 ～ 1999 年平均）。实（虚）线为正（负）距平。实（虚）线代表（ TP–TIO ）经向梯度加强（减弱）。可见对流层中上部 TP 以及其以南地区的经向温度梯度减弱（单位： K ）

Continued weakening of meridional temperature gradient between TP and TIO in the future (2080-2099)

The left panels show the 2001-2100 trend in mm/day (21-model average), and the right panels show the number of models (of 21) that have an increasing trend. The figure is adapted from Christensen et al. (Regional Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental

Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA).

Projected change in precipitation amount over the Asian-Australian monsoon region in June-August due to human-induced climate change using the Coupled

Model Intercomparison Project-3 models.

谢谢！