一次江淮流域切变綫过程的研究

A CASE STUDY OF LOW LEVEL SHEAR LINE OVER YANGTZE-HWIA VALLEY IN CHINA

中文摘要:

      本文研究一次江淮流域切变线的生成及其各个发展阶段的結构。关于切变线的生成原因,作者强調高原的动力及热力影响。在結构方面,作者指出,切变綫附近鉛直环流的形式、切变线附近气象要素的分布以及低空鋒区的加强,相互之間有着密切联系.鉛直环流的加强,造成了低空鋒区的加强。当这个环流圈相对于鋒面的位置有变化时,鋒面的性貭,也就有不同。在切变线的上升运动区上空,高层对流层中,可能存在一下沉运动带,因而与切变线有关的流場,至少涉及到整个对流层。最后,作者討論了:鉛直环流对鋒面的作用、极鋒型鋒区向赤道鋒的轉变以及我国副热带夏季某些系統的性貭及其特点等問題。

英文摘要:

      During summer very often there is a heavy-rain bearing west-east shear line in the lower troposphere over Yangtze-Hwai valley. To the north of the shear line, the wind is predominantly from east or northeast, and to the south from the west or southwest. Its appearance is most evident on 850 and 700 mb surface. In this paper a case study of this type of shear line is made. It is shown that the dynamical and thermal effects of Tibet plateau is the one of the important factors for its formation.The analysis of the three dimensional wind field in the region of the shear line, shows that the pattern of the vertical circulation has an important influence on the horizontal distribution of temperature and humidity near the shear line, thus it is closely related to the genesis and development of the. low level frontal zone. Moreover, several problems concerning the synoptic meteorology in subtropics over Far East during summer are discussed. They include:the influence of vertical circulation on the frontal zone;the process of the transformation of a polar front into an equatorial front and the nature of the some weather systems in subtropical region of China in summer. The author has offered several explanations about these characteristics.