2009年丹东地区罕见伏旱天气成因分析

Analysis of formation reason of rare summer drought in 2009 in Dandong,Liaoning province

2009年丹东地区不仅没有气象意义上的主汛期,而且发生了持续时间居历史第3位的伏旱天气。阐述了2009年丹东地区伏旱天气事实,探讨了伏旱成因机理。结果表明:造成2009年中国丹东地区伏旱天气的直接原因并不是历史上常见的西太平洋副热带高压西伸北跳和"588线"控制丹东地区。与之相反,伏旱事件期间,副热带高压位置稳定偏南,极涡位置主体偏北,中国丹东地区持续受西风带纬向环流控制,导致冷空气南下引导受阻,高层南亚高压在高温期有明显的北抬东伸。台风活动路径偏西、偏南,使副热带高压维持偏南而无明显西伸北跳,也是导致全区干旱少雨的主要原因。此外,全球气候变暖大背景和日益明显的城市化效亦与伏旱天气事件的发生有关。

The main flood season is not significant in 2009 in Dandong,and summer drought occurs and its duration is the third in historical record.The characters and formation mechanism of summer drought were analyzed.The results show that the west pacific subtropical high and ＂588＂ line are not the direct reasons of this summer drought.Contrarily,the location of subtropical high is stable and leans to the south in this event and the location of polar vortex leans to the north.The zonal circulation of westerly belt controls Dandong area,which makes cold air moving to the south disturbed,so the south Asia high strengthens obviously and stretches eastwardly during the high temperature period.The path of typhoon moves to the west and further southward and it makes subtropical high southward,which is the important reason of summer drought in Dandong.Furthermore,the global climate warming and the urbanization are also the indirect factors of summer drought.