The interdecadal factors affecting the summer monsoon winds over Somalia and the South China Sea were studied. Global geopotential heights and wind velocity fields of the 850-hPa and 200-hPa pressure levels, as well as sea surface temperature anomaly data and correlation coefficients were analyzed. The monsoons over Somalia and the South China Sea were found to be two different monsoon systems, operating on different mechanisms and being affected by different oceanatmosphere interactions. The intensity of the Asian subtropical summer monsoon is influenced by the intensity of the summer monsoon over Somalia in the month of June and by the intensity of the summer monsoon over the South China Sea in the months of June and July. The summer monsoon wind strength over Somalia is affected by regional factors, such as the heating of the Tibetan plateau, and by global mechanisms, such as the subtropical heat exchange with Antarctica. The summer monsoon over the South China Sea is affected by different ocean-atmosphere interactions. The Somalia and subtropical summer monsoons have wind blowing down the pressure gradient from area over ocean to that over land, like typical summer monsoons. The South China Sea summer monsoon has winds that blow down the pressure gradient from area over land to that over ocean. The South China Sea summer monsoon is affected by the Kuroshio Current off the east coast of Japan.
In this article, a sensitivity test of air-sea surface flux model was carried out with the field observation data of Project “South China Sea Air-Sea Flux Measurement in 2000”. The results show that sensible heat fluxes are sensitive to observation errors, increasing the error of model calculation; In contrast, the latent heat flux and momentum flux are not as sensitive to observation errors as the sensible heat, and their calculated results are reliable. The test result also verifies the rationality of the surface flux values calculated and the conclusions can be used to detect errors in observed data.
Using monthly mean atmospheric re- analysis data and oceanic assimilation data product,the winter ocean-atmosphere interaction in middle and high latitude in Northwest Pacific was studied. Key regions were chosen to study the variations of Aleutian Low,the 500hPa westerly,the meriodional sea surface temperature (SST) gradient with three indices defined as Aleutian Low index,zonal index and meridional SST gradient between Kuroshio- influenced region and Oyashio-influenced region. The results show that when there is a deeper Aleu- tian Low accompanied by a stronger northerly wind in the western part of the Aleutian Low,the subpolar gyre of North Pacific is strengthened,the SST in the Oyashio-influenced region is decreased and the me- ridional SST gradient between Kuroshio-influ- enced region and Oyashio-influenced region is increased,which,in turn,will enhance the westerly jet in the upper troposphere due to thermal-wind relation. The strengthened westerly jet makes a favorable condi- tion for the deeper Aleutian Low over North Pacific beneath the left part of the jet exit region. Conse- quently,a positive feedback forms there.
应用热带太平洋上层XBT温度资料,分析探讨了西太平洋暖池区次表层海温冷暖异常信号的变化规律,揭示了影响西太平洋暖池区次表层海温冷暖异常信号的机制。分析表明,西太平洋暖池区的次表层海温异常冷暖与太平洋北赤道流的海温冷暖异常信号西传有重要关系。北赤道流的海温异常冷(暖)信号是沿温跃层由赤道中东太平洋潜沉向西太平洋暖池区传播,对暖池区域次表层海温场产生重要影响。这一传播过程与西太平洋次表层海温异常暖(冷)信号向赤道中东太平洋传播,构成了热带海洋信号的气旋式“信号通道”。在这一“信号通道”中,北赤道流的海温异常信号西传是导致西太平洋暖池区及西太平洋次表层海温异常的重要机制,是影响El Nino和 La Nina事件发生的关键。
