MODELING THE IMPACT OF THE WESTERN PACIFIC SEA SURFACE TEMPERATURE DIFFERENCE ON THE ASIAN SUMMER MONSOON CLIMATE AT THE LAST GLACIAL MAXIUM
Sui Weihui Zhao Ping(Chinese Academy of Meteorological Sciences,Beijing 100081)
The climate conditions during the Last Glacial Maximum (LGM) have been always a important scientific question,documenting the characteristics of the past climates. Understanding the causes of climate change has been major challenges in studying the earth system. Both the present and past climate systems reveal the role of tropical oceans,particularly the importance of the Pacific warm pool. However,studies that aim at the impact of the western Pacific sea surface temperature (SST) anomaly on Asian summer monsoon during the LGM are rare and there still exist uncertainty of tropical western Pacific SST reconstruction in simulating the LGM climate. Thus, it is important to evaluate the effects of the different reconstructed LGM SSTs on ice age Asian summer monsoon simulations and understand what extent do the SST anomaly affect the Asian summer monsoon simulations uncertainty,which conduces to recover the climate conditions during the LGM more reasonably. The impact of the western Pacific SST difference between the Wang reconstruction and the Climate,Long-Range Investigation,Mapping and Prediction (CLIMAP) project's reconstruction on Asian summer monsoon during the Last Glacial Maximum,have been investigated using the NCAR's CCM3 and the same two experiments, data as Zhao et al,the two experiments are the W-LGM experiment and C-LGM experiment respectively. General speaking the western Pacific SST in the W-LGM experiment is warmer in summer (6~8 month average) than that in the C-LGM experiment. Our modeling results indicate that there is a significant change in Asian summer monsoon between the two experiments because the western Pacific SST anomaly. In summer (6~8 month average),when the tropical western Pacific SST is warmer between 140°E and 160°E,atmosphere heat of locality and Indian region all have significantly corresponding increase. South Africa high and the South Indian ocean meridional[CS] Hadley circulation are all intensified which make Somali cross-equatorial current stronger,on the other hand the zonal monsoon circulation in the Indian monsoon region is also strengthened,with the result of these, the Indian summer monsoon strengthen,meantime low level water vapor[CS] transport and water vapor[CS] transport convergence increase, ascending strengthen and rainfall increase in the Indian monsoon region finally;inversely, [CS]Australia high weaken which induces cross-equatorial current weaken about 120°E,furthermore meridional[CS] monsoon circulation south of 20°N is strengthened,zonal monsoon circulation north of 20°N is weakened,these feature show South China Sea summer monsoon is strengthened,while East Asian subtropical continental summer monsoon is weakened.
【Fund】： 国家自然科学基金重点项目(批准号:40231011);; 国家重点基础研究发展规划项目(批准号:G2000078502)资助
【CateGory Index】： P467
【CateGory Index】： P467