摘要
利用再分析的陆地降水、环流和辐射数据,以及表征大气波动的指数,对比了1951—2020年期间El Nino春季快速衰减年和缓慢衰减年的东亚环流和华北夏季降水异常情况,并从大气波动强度的角度探讨了为何El Nino在一些年份的春季会发生快速衰减。结果表明,相较于其他不发生El Nino衰减的年份,El Nino春季快速衰减年华北7、8月的降水量显著偏多,尤其是8月;而El Nino缓慢衰减年夏季,华北降水相较其他年份偏多不明显。El Nino春季快速衰减年6—8月850 hPa上菲律宾到南海存在异常反气旋,其强度强于El Nino缓慢衰减年;El Nino春季快速衰减年8月500 hPa西太平洋副热带高压(西太副高)显著偏北,而缓慢衰减年西太副高偏北的特征不明显,而是以偏西为主;200 hPa副热带西风急流在El Nino春季快速衰减年8月显著偏北,而在El Nino缓慢衰减年中反而略偏南;El Nino春季快速衰减年6—8月沃克环流显著偏强,相比之下El Nino缓慢衰减年沃克环流偏强的特征要弱很多。上述环流异常特征为El Nino春季快速衰减年华北7—8月降水异常偏多提供了有利条件。通过近地面风场合成分析发现,春季El Nino快速衰减月前后,赤道中西太平洋异常东风爆发非常明显,而El Nino缓慢衰减年的异常东风信号较弱。春季El Nino快速衰减前印度洋对流活动非常强盛,并向海洋性大陆传播,这种对流可能通过不断激发大气波动,继而引发近地面东风爆发,最终导致El Nino出现快速衰减。
Based on reanalysis datasets of land precipitation,circulation,radiation,and indices representing atmospheric waves,anomalies of the East-Asian circulation and the summer precipitation in North China of the years in which El Nino decayed fast in spring are compared with those of El Nino slow decaying years between 1951—2020;And the reason why El Nino decayed fast in spring in some years was discussed from the perspective of atmospheric wave intensity.Results show that,compared with the other years without El Nino decaying,the precipitation in North China in July and August of the fast decaying years are significantly greater,especially in August.In contrast,the summer precipitation in North China are not significantly greater in the slow decaying years.There was an anomalous anticyclone at 850 hPa over the Philippines to the South China Sea from June to August in the fast decaying years,which was much stronger than that in the slow decaying years.The western Pacific subtropical high(WPSH)at 500 hPa was significantly northward-displaced in August in the fast decaying years,while the WPSH in the slow decaying years was more westward rather than northward.The 200 hPa subtropical westerly jet in August of the fast decaying years was significantly northward,while the corresponding westerly jet in the slow decaying years was slightly southward.And the Walker Circulation from June to August in the fast decaying years was much stronger than that in the slow decaying years.These circulation anomalies in the fast decaying years provided favorable conditions for more precipitation in North China from July to August.According to the composite analysis of near-surface wind,the outbreak of anomalous equatorial easterly wind occurred around the month in which El Nino decayed fast over the Western and Central Pacific.However,in the slow decaying years,the anomalous equatorial easterly wind was much weaker and unsignificant.The convection over the Indian Ocean remained active and spread to the Maritime continent during the fast
作者
孔铃涵
朱锦涛
赵树云
王五科
马馨宇
KONG Linghan;ZHU Jintao;ZHAO Shuyun;WANG Wuke;MA Xinyu(Department of Atmospheric Science,School of Environmental Studies,China University of Geosciences,Wuhan 430078,China;Department of Atmospheric Science,CMA-CUG Joint Centre for Severe Weather and Climate and Hydrogeological Hazards,China University of Geosciences,Wuhan 430074,China)
出处
《大气科学学报》
CSCD
北大核心
2023年第4期517-531,共15页
Transactions of Atmospheric Sciences
基金
国家重点研发计划项目(2019YFE0125000)
国家自然科学基金资助项目(42005128)。
