影响大西洋热带风暴Debby(2006)的干空气源地分析

TRACKING DRY AIR SOURCES THAT AFFECT ATLANTIC TROPICAL STORM DEBBY(2006)

干空气影响热带气旋活动的研究受到越来越多的重视。大西洋地区热带气旋的活动不仅受撒哈拉干暖空气层(SAL)的影响,还受副高下沉干空气的影响。通过模拟2006年大西洋地区SAL的活动以及热带风暴Debby等热带气旋的活动,着重研究影响Debby三个不同发展阶段的干空气源地。研究发现,从对流层中层进入热带风暴内核地区的干空气,除了以上两个源地外还包括来自中纬度对流层低层的干空气,以及来自中高纬度下沉气流的干空气。在Debby生成之初,中层有35.7%的格点气团来自干空气,其中51.9%来自SAL的干空气,剩余的干空气分别来自副高下沉气流及中纬度对流层低层运动的干空气。随着Debby逐渐向西北方向移动,来自SAL的干空气逐渐减少,来自中高纬度下沉气流的干空气逐渐占主导。

Increasing attention has been paid to the impact of dry air on Atlantic tropical cyclone activity.Using numerical simulation data,the sources of dry air that affects Tropical Storm Debby （2006） are tracked through calculating the trajectories of the dry air that penetrates into the inner areas of the storm at its middle levels.Four sources of the dry air are identified based on the trajectory calculation.In agreement with previous studies,the dry air can come from the subsidence associated with the subtropical high over West Africa and the Saharan air layer （SAL）.In addition,we find that a considerable amount of dry air can come from mid-latitudes lower and middle troposphere.At the early stage of Debby,dry air accounts for 35.7％ of the total air at middle levels,among which 51.9％ dry air is from the SAL.As Debby moves northwestward,the influence of the SAL dry air decreases,while the dry air from middle latitudes becomes important.