Steady decline of East Asian Monsoon Winds, 1969-2000: Evidence from direct ground measurements of wind speed

Download
Author
Xu M.
Chang, C.-P.
Fu, C.
Ye,Qi
Robock. A.
Robinson, D.
Zhang, H.
Date
2006Metadata
Show full item recordAbstract
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. 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.
Description
J. Geophy. Res., 111, D24111
The article of record as published may be located at http://dx.doi.org/10.1029/2006JD007337
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
Related items
Showing items related by title, author, creator and subject.
-
A Theory for the Tropical Tropospheric Biennial Oscillation
Chang, C.-P.; Li, Tim (2000-07-15);The key questions of how the tropospheric biennial oscillation (TBO) maintains the same phase from northern summer in South Asia to southern summer in Australia, and how the reversed phase can last through three locally ... -
Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part I: Roles of the Subtropical Ridge
Chang, C.-P.; Zhang, Yongsheng; Li, Tim (2000-12);The interannual relationship between the East Asian summer monsoon and the tropical Pacific SSTs is studied using rainfall data in the Yangtze River Valley and the NCEP reanalysis for 1951–96. The datasets are also partitioned ... -
Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part I: Roles of the Subtropical Ridge
Chang, C.-P.; Zhang, Y.; Li, T. (American Meteorological Society, 2000);The interannual relationship between the East Asian summer monsoon and the tropical Pacific SSTs is studied using rainfall data in the Yangtze River Valley and the NCEP reanalysis for 1951-96. The datasets are also partitioned ...