Characteristics of Rainfall Structure over the Tropical Pacific during the Later Period of 1997/1998 El Ni o Derived from TRMM PR Observations
Characteristics of Rainfall Structure over the Tropical Pacific during the Later Period of 1997/1998 El Ni o Derived from TRMM PR Observations
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发表时间：
2005
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通讯作者：
Fu Yun
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作者：
Fu Yun
利用热带降雨测量任务（TRMM）降水雷达（PR）观测资料，分析了1997/1998年厄尔尼诺后期热带太平洋的降水结构，并与1999/2000年非厄尔尼诺年份同期的降水结构进行了比较。结果表明，1997/1998年厄尔尼诺后期，热带东太平洋和中太平洋的层状雨和对流雨的面积分量和平均降雨量均高于1999/2000年非厄尔尼诺同期。1997/1998年厄尔尼诺后期，两地区强层状降水显著增加，弱层状降水显著减少。1999/2000年非厄尔尼诺n~o期降水垂直结构表现为太平洋东部和中部对流降水较浅，层状降水亮带高度较低。然而，在1997/1998年厄尔尼诺后期，由于海温增加，这两个地区的对流降雨变深，层状亮带高度增加。结果表明，1997/1998年厄尔尼诺后期与非厄尔尼诺时期相比，对流和层状雨的增长率随海拔高度的变化都很显著。1997/1998年后期，由于海温异常和热带太平洋降水结构的变化，热带太平洋上空出现了较弱的Walker环流。
Based upon the Tropical Rainfall Measuring Mission (TRMM) Precipitaton Radar (PR) measuring data, the rainfall structures over the tropical Pacific Ocean during the later period of 1997/1998 El Ni n～o are analyzed, and compared with those in the same period of the non-El Ni n～o years in 1999/2000. Results indicate higher area fractions and averaged rainfall rates for both stratiform and convective rains over the tropical eastern and central Pacific Ocean in the later period of 1997/1998 El Ni n～o than in the same period of non-El Ni n～o in 1999/2000. Results also show the significant increase of heavy stratiform rain and decrease of weak stratiform rain over both the regions in the later period of 1997/1998 El Ni n～o. During the non-El Ni n～o period of 1999/2000, the vertical structures of precipitations show shallower convective rain, and lower brightband altitudes of stratiform rain over the eastern and central Pacific Ocean compared with those over the tropical western Pacific Ocean. However, during the later period of 1997/1998 El Ni n～o, the convective rains become deeper and the stratiform brightband altitudes increase over both the regions due to SSTA increases over there. Results expose significant variations of the growth rate of both convective and stratiform rain with altitude in the later period of 1997/1998 El Ni n～o compared with that in the non-El Ni n～o period. Atmospheric circulations display the pattern changes of convergences and divergences in the upper atmosphere layer, and a weaker Walker circulation over the tropical Pacific Ocean in the later period of 1997/1998 El Ni n～o as resulted from SSTA and precipitation structure changes over there.