热带气旋外围环流中次天气尺度系统及其与天气尺度系统相互作用的诊断分析

本文应用带通滤波的方法,分离出热带气旋外围环流中的天气尺度和次天气尺度系统。发现热带气旋外围强降水与低层次天气尺度系统的辐合关系相当密切。文中还计算了两种尺度系统间的动能和涡度转换。得出:在650hPa以上基本上是天气尺度系统向次天气尺度系统提供动能,在650hPa以下基本上是次天气尺度系统向天气尺度系统提供动能,整层积分的结果是天气尺度系统向次天气尺度系统提供动能。在900hPa和400hPa之间的涡度转换为次天气尺度系统向天气尺度系统转换,即涡度转换的结果是使得次天气尺度系统气旋性减弱,天气尺度系统气旋性增强。900hPa以下和400hPa以上则相反。整层积分的结果是次天气尺度系统向天气尺度系统提供正涡度。 

SUBSYNOPTIC SYSTEMS IN THE OUTER CIRCULATION OF TROPICAL CYCLONES AND THEIR INTERACTIONS WITH SYNOPTIC SYSTEMS

A band-pass filter is used to separate synoptic systems from subsynoptic ones in the outer circulations of tropical cyclones, disclosing that the severe outer precipitation shows close relations of convergence with low-level synoptic scale systems. In the paper’s computation of exchanges of momentum and vorticity between the two systems, it is known that the transfer of momentum is langely from synoptic systems to subsynoptic ones for levels higher than 650 hPa and the opposite process takes place for levels lower than it, while the momentum moves from synoptic systems to subsynoptic ones in integrations for the full layer. In the exchange of vorticity, the direction is from subsynoptic systems to synoptic ones for levels between 900 and 400 hPa, i. e. consequently , subsynoptic systems get less cyclonic and synoptic ones more cyclonic. The direction is the opposite for levels below 900 hPa or above 400 hPa. Full layer integrations suggest transfers of positive vorticity from subsynoptic scale systems to synoptic ones.