南海夏季风爆发过程合成分析
COMPOSITE ANALYSIS OF SUMMER MONSOON ONSET PROCESS OVER SOUTH CHINA SEA
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摘要: 采用合成分析方法研究了南海夏季风的爆发过程及其前期征兆。研究结果表明,在南海夏季风爆发之前,对流首先在中南半岛出现,随后在临近南海夏季风爆发时,菲律宾附近也出现对流活动,这表明菲律宾附近对流活动的出现也是引起南海夏季风爆发的原因之一。在南海夏季风爆发之前,赤道印度洋上(75～95°E)的赤道西风有一次明显的增强过程,它对南海夏季风的爆发也起了十分重要的作用,因为一方面它通过赤道西风的东扩促使南海南部的赤道西风建立和增强;另一方面,它又通过西风的北抬以及激发孟加拉湾的对流扰动发展和北移东传,诱使我国华南沿海西风的增强和南压,从而对南海夏季风爆发产生影响。进一步的研究还表明,印度洋赤道西风和南海南部赤道西风的增强又分别与南半球马斯克林高压、澳大利亚高压的增强以及索马里、85°E附近和105 °E附近向北越赤道气流的增强有关。Abstract: Based on the method of composite analysis,the onset process of summer monsoon over South China Sea (SCS) is investigated. Result indicates that convection activities firstly appear over Indo-China peninsula prior to the onset of the monsoon,then occur around Philippines as the monsoon begins immediately,implying that the convection activities around Philippines serve as one of the reasons leading to the SCS monsoon onset. Before the SCS monsoon onset,the equatorial westerly over the Indian Ocean (75～95°E) experiences noticeable enhancement and plays an important role on the SCS monsoon onset. On the one hand,it propagates eastward rapidly and causes the establishment and strengthening of equatorial westerly in the southern SCS,on the other hand,it results in the migration southward of the westerly on south side of the south-China stationary front by means of shift northeastward of the westerly and convection over the Bay of Bengal. Further study also shows that the intensification of equatorial westerly in the Indian Ocean (75～95°E) and the southern SCS is closely related to the reinforcement of the southern-hemisphere Mascarene high and Australian high,and cross-equatorial flow northward around Somali,85 and 105 ℃E,respectively.
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Key words:
- summer monsoon overSouth China Sea /
- onset process /
- composite analysis
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