Modulation of Low-Latitude West Wind on Abnormal Track and Intensity of Tropical Cyclone Nargis (2008) in the Bay of Bengal  

作　　者：LI Wei-Wei WANG Chunzai WANG Dongxiao YANG Lei DENG Yi 李维维;王春在;王东晓;杨磊;邓奕(State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Science,Guangzhou 510301;NOAA/Atlantic Oceanographic and Meteorological Laboratory,Miami,Florida,USA)

机构地区：[1]State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Science,Guangzhou 510301 [2]NOAA/Atlantic Oceanographic and Meteorological Laboratory,Miami,Florida,USA

出　　处：《Advances in Atmospheric Sciences》2012年第2期407-421,共15页大气科学进展（英文版）

基　　金：supportedby a grant from the Major State Basic Research Development Program of China(973Program)(No2011CB403500);the National Natural Science Foundation of China(NSFC)(NoU0733002);the Natural Science Foundation of Guangdong Province,China(No8351030101000002)

摘　　要：Tropical cyclone （TC） Nargis （2008） made landfall in Myanmar on 02 May 2008, bringing a storm surge, major flooding, and resulting in a significant death toll. TC Nargis （2008） displayed abnormal features, including rare eastward motion in its late stage, rapid intensification before landing. Using reanalysis data and a numerical model, we investigated how a low-latitude westerly wind modulated TC Nargis’ （2008） track and provided favorable atmospheric conditions for its rapid intensification. More importantly, we found a possible counterbalance effect of flows from the two hemispheres on the TC track in the Bay of Bengal. Our analysis indicates that a strong westerly wind burst across the Bay of Bengal, resulting in TC Nargis’ （2008） eastward movement after its recurvature. This sudden enhancement of westerly wind was mainly due to the rapidly intensified mid-level cross-equatorial flow. Our results show that a high-pressure system in the Southern Hemisphere induced this strong, mid-level, cross-equatorial flow. During the rapid intensification period of TC Nargis （2008）, this strong and broad westerly wind also transported a large amount of water vapor to TC Nargis （2008）. Sufficient water vapor gave rise to continuously high and increased mid-level relative humidity, which was favorable to TC Nargis’ （2008） intensification. Condensation of water vapor increased the energy supply, which eventuated the intensification of TC Nargis （2008） to a category 4 on the Saffir-Simpson scale.Tropical cyclone （TC） Nargis （2008） made landfall in Myanmar on 02 May 2008, bringing a storm surge, major flooding, and resulting in a significant death toll. TC Nargis （2008） displayed abnormal features, including rare eastward motion in its late stage, rapid intensification before landing. Using reanalysis data and a numerical model, we investigated how a low-latitude westerly wind modulated TC Nargis’ （2008） track and provided favorable atmospheric conditions for its rapid intensification. More importantly, we found a possible counterbalance effect of flows from the two hemispheres on the TC track in the Bay of Bengal. Our analysis indicates that a strong westerly wind burst across the Bay of Bengal, resulting in TC Nargis’ （2008） eastward movement after its recurvature. This sudden enhancement of westerly wind was mainly due to the rapidly intensified mid-level cross-equatorial flow. Our results show that a high-pressure system in the Southern Hemisphere induced this strong, mid-level, cross-equatorial flow. During the rapid intensification period of TC Nargis （2008）, this strong and broad westerly wind also transported a large amount of water vapor to TC Nargis （2008）. Sufficient water vapor gave rise to continuously high and increased mid-level relative humidity, which was favorable to TC Nargis’ （2008） intensification. Condensation of water vapor increased the energy supply, which eventuated the intensification of TC Nargis （2008） to a category 4 on the Saffir-Simpson scale.

关 键 词：TC Nargis （2008） tropical cyclone westerly wind cross-equatorial flow Bay of Bengal 

分 类 号：P444[天文地球—大气科学及气象学]