亚洲季风区海陆热力差异演变规律及其对季风的影响研究

Ocean-continent heating anomalies, or ocean-continent thermal contrasts are the major reason for the formation of monsoon. On the other hand, some features of ocean-continent thermal anomalies can also be identified through the onset of monsoon. Some issues arise from where are the monsoon regions on the globe scale and how to determine the onset of monsoon. For these questions, a key issue is how to find an ideal definition of monsoon. The tranditional difinition is based on the both the seasonal reversals of wind direction and the transition of dry/wet climates. Synthesizing the two difinitions and linking to the cross-equatotial flow, a new definition, the summer monsoon in the subtropics has been defined as an expansion of the atmospheric wet convective centers associated with tropical monsoon flows. Three large water vapor centers with the largest one in the region between Asia and Australia are identified through the analysis of water vapor brightness temperature (BT) monitorized by polar orbiting satellites. The strength and domain variations of the largest water-vapor center lead the seasonal, interannual and interdecadal variability of the Asian-Australian monsoon. According to the new difinition, the earlest onset of Asian summer monsoon is found in the Indo-china peninsula and then onset at the 28th pentad (mid May) in the central part of the South China Sea (SCS). After the onset of the SCS monsoon, the South Asian monsoon and the East Asian monsoon are linked through southwesterly monsoon flow and monsoon rain belt, marking the northward advance for the Asian summer monsoon as whole. The speed of northward advance and the reached latitudes are varid due to different local thermal contrasts. The nature of monsoon rainfall in the East Asian region is different from the tropical rainfall in the South Asian region. An oscillation with timescale about 20 days is found in the East Asian monsoon region during summer spell.. Findings suggest that the summer monsoons over many subtropical regions can be defined by both cross-equatorial flows and dry/wet spell transitions. In the mid- and low-latitudes, there exist six major dry/wet spell transition regions with a dry or wet period lasting more than one month. The region of most significant change is located over the subtropical North Africa-Asia-northwest Pacific. The others appear over subtropical South Africa, Indonesia-Australia, southwest Pacific, the Mexico-Caribbean Sea, and subtropical South America. . The thermal features in the tropical and subtropical Indian Ocean, and subsurface thermal features in the Indian Ocean and Pacific Ocean are also used to study the air-sea interactions in these basins..

我国降水异常与东亚季风的年际变化密切相关，季风的形成和发展主要决定于下垫面的海陆热力差异。但在降水预报实践中，海温和土壤温度却被作为独立因子加以考虑。由于亚洲季风大部分地区缺乏可供研究所用的资料，对海陆热力差异的时空变化规律尚无研究。本项目整编世界数据中心所提供的最新海洋-地温资料集，在重新分析海陆热力差异的基础上，探趾Ｂ饺攘Σ钜斓谋浠媛杉捌湓诩痉缪荼渲械淖饔茫剿髌湓谄蛟げ庵械挠τ谩