Steady decline of east Asian monsoon winds, 1969–2000: Evidence from direct ground measurements of wind speed

[1] It is commonly believed that greenhouse-gas-induced global warming can weaken the east Asian winter monsoon but strengthen the summer monsoon, because of stronger warming over high-latitude land as compared to low-latitude oceans. In this study, we show that the surface wind speed associated with the east Asian monsoon has significantly weakened in both winter and summer in the recent three decades. From 1969 to 2000, the annual mean wind speed over China has decreased steadily by 28%, and the prevalence of windy days (daily mean wind speed > 5 m/s) has decreased by 58%. The temperature trends during this period have not been uniform. Significant winter warming in northern China may explain the decline of the winter monsoon, while the summer cooling in central south China and warming over the South China Sea and the western North Pacific Ocean may be responsible for weakening the summer monsoon. In addition, we found that the monsoon wind speed is also highly correlated with incoming solar radiation at the surface. The present results, when interpreted together with those of recent climate model simulations, suggest two mechanisms that govern the decline of the east Asian winter and summer monsoons, both of which may be related to human activity. The winter decline is associated with global-scale warming that may be attributed to increased greenhouse gas emission, while the summer decline is associated with local cooling over south-central China that may result from air pollution.

[1]  Tim Li,et al.  Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part I: Roles of the Subtropical Ridge , 2000 .

[2]  C. Long,et al.  From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth's Surface , 2005, Science.

[3]  D. Yihui,et al.  Monsoons over China , 1993 .

[4]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[5]  Mark Henderson,et al.  A spatial analysis of pan evaporation trends in China, 1955–2000 , 2004 .

[6]  Martin Wild,et al.  On the consistency of trends in radiation and temperature records and implications for the global hydrological cycle , 2004 .

[7]  Yuqing Wang,et al.  Observed trends in extreme precipitation events in China during 1961–2001 and the associated changes in large‐scale circulation , 2005 .

[8]  S. Min,et al.  Future Projections of East Asian Climate Change from Multi-AOGCM Ensembles of IPCC SRES Scenario Simulations , 2004 .

[9]  O. Varis,et al.  Climate Change in China , 2001, Ambio.

[10]  John M. Wallace,et al.  The Pacific Center of Action of the Northern Hemisphere Annular Mode: Real or Artifact? , 2001 .

[11]  E. Feil,et al.  Climate Effects of Black Carbon Aerosols in China and India , 2002 .

[12]  Xubin Zeng,et al.  Globally Unified Monsoon Onset and Retreat Indexes , 2004 .

[13]  David R. Easterling,et al.  Global warming : evidence for asymmetric diurnal temperature change. , 1991 .

[14]  Yuqing Wang,et al.  Correction to “Observed trends in extreme precipitation events in China during 1961–2001 and the associated changes in large‐scale circulation” , 2005 .

[15]  D. Gaffen,et al.  Late-Twentieth-Century Climatology and Trends of Surface Humidity and Temperature in China , 2001 .

[16]  Qun Xu,et al.  Abrupt change of the mid-summer climate in central east China by the influence of atmospheric pollution , 2001 .

[17]  Chang‐Hoi Ho,et al.  Shift in the summer rainfall over the Yangtze River valley in the late 1970s , 2002 .

[18]  Du Zheng,et al.  Moisture conditions and climate trends in China during the period 1971–2000 , 2006 .

[19]  Xin-Zhong Liang,et al.  The Monsoon Rainband over China and Relationships with the Eurasian Circulation , 1999 .

[20]  Guo Qiyun.  Interdecadal Variability of East-Asian Summer Monsoon and Its Impact on the Climate of China , 2003 .

[21]  David A. Robinson,et al.  Land surface conditions over Eurasia and Indian summer monsoon rainfall , 2003 .

[22]  A. Haines.  Climate change 2001: the scientific basis. Contribution of Working Group 1 to the Third Assessment report of the Intergovernmental Panel on Climate Change [Book review] , 2003 .

[23]  W. Collins,et al.  The NCEP–NCAR 50-Year Reanalysis: Monthly Means CD-ROM and Documentation , 2001 .

[24]  M. Hori,et al.  Impact of global warming on the East Asian winter monsoon as revealed by nine coupled atmosphere‐ocean GCMs , 2006 .

[25]  A. Sumi,et al.  Interannual-Interdecadal Variation in Large-Scale Atmospheric Circulation and Extremely Wet and Dry Summers in China/Japan during 1951-2000 Part II: Dominant Timescales , 2004 .

[26]  Mark Henderson,et al.  Taking China's Temperature: Daily Range, Warming Trends, and Regional Variations, 1955–2000 , 2004 .

[27]  J. Chan,et al.  A Unified Monsoon Index for South China , 1999 .

[28]  J. Hansen,et al.  Climate Effects of Black Carbon Aerosols in China and India , 2002, Science.

[29]  D. Houghton,et al.  THE IMPACT OF INDIAN OCEAN SST ON THE LARGE-SCALE ASIAN SUMMER MONSOON AND THE HYDROLOGICAL CYCLE , 1996 .

[30]  Congbin Fu,et al.  Potential impacts of human-induced land cover change on East Asia monsoon , 2003 .

[31]  Interannual-Interdecadal Variation in Large-Scale Atmospheric Circulation and Extremely Wet and Dry Summers in China/Japan during 1951-2000 Part I: Spatial Patterns , 2004 .

[32]  Ming Xu,et al.  Observed trends of precipitation amount, frequency, and intensity in China, 1960–2000 , 2005 .

[33]  Recent progress in the joint agreements on Global and Regional Climate Change studies between the United States and the People's Republic of China , 2000 .

[34]  Jinho Yoon,et al.  Interannual Variation in Indochina Summer Monsoon Rainfall: Possible Mechanism , 2000 .

[35]  Bin Wang,et al.  EAST ASIAN MONSOON-ENSO INTERACTIONS , 2004 .

[36]  Zhongwei Yan,et al.  The East Asian summer monsoon circulation anomaly index and its interannual variations , 1999 .

[37]  K. Lau,et al.  Interannual Variability of the Asian Summer Monsoon: Contrasts between the Indian and the Western North Pacific–East Asian Monsoons* , 2001 .

[38]  Bin Wang,et al.  Tropospheric cooling and summer monsoon weakening trend over East Asia , 2004 .

[39]  Xue Feng,et al.  Interannual to interdecadal variation of east asian summer monsoon and its association with the global atmospheric circulation and sea surface temperature , 2001 .

[40]  M. Yanai,et al.  The onset and interannual variability of the Asian summer monsoon in relation to land-sea thermal contrast , 1996 .