Responses of East Asian summer monsoon to historical SST and atmospheric forcing during 1950–2000 |
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| Authors: | Hongmei Li Aiguo Dai Tianjun Zhou Jian Lu |
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| Institution: | (1) LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China;(2) National Center for Atmospheric Research, Boulder, CO, USA;(3) Graduate School of Chinese Academy of Sciences, Beijing, China |
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| Abstract: | The East Asian summer monsoon (EASM) circulation and summer rainfall over East China have experienced large decadal changes
during the latter half of the 20th century. To investigate the potential causes behind these changes, a series of simulations
using the national center for atmospheric research (NCAR) community atmospheric model version 3 (CAM3) and the geophysical
fluid dynamics laboratory (GFDL) atmospheric model version 2.1 (AM2.1) are analyzed. These simulations are forced separately
with different historical forcing, namely tropical sea surface temperature (SSTs), global SSTs, greenhouse gases plus aerosols,
and a combination of global SSTs and greenhouse gases plus aerosols. This study focuses on the relative roles of these individual
forcings in causing the observed monsoon and rainfall changes over East Asia during 1950–2000. The simulations from both models
show that the SST forcing, primarily from the Tropics, is able to induce most of the observed weakening of the EASM circulation,
while the greenhouse gas plus (direct) aerosol forcing increases the land-sea thermal contrast and thus enhances the EASM
circulation. The results suggest that the recent warming in the Tropics, especially the warming associated with the tropical
interdecadal variability centered over the central and eastern Pacific, is a primary cause for the weakening of the EASM since
the late 1970s. However, a realistic simulation of the relatively small-scale rainfall change pattern over East China remains
a challenge for the global models. |
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