用铁塔资料研究地面冷锋的结构  

A STUDY OF THE STRUCTURE OF COLD FRONT NEAR SURFACE USING TOWER DATA

作　　者：苗曼倩[1] 赵鸣[1] 潘裕强[1] 

机构地区：[1]南京大学大气科学系

出　　处：《南京大学学报（自然科学版）》1994年第3期541-550,共10页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金

摘　　要：利用铁塔的梯度观测资料研究夜间干冷锋过境时的边界层结构和部分地面锋面特征．资料表明近地面处，锋面与地表面近于垂直．锋面附近垂直运动很强，只比水平风速小一个量级．表征湍流交换强度的总体拖曳系数ＣＤ和热量输送系数ＣＨ在锋面过境前后有明显的响应．并存在着明显的日变化．陆面上白天的ＣＤ和ＣＨ值较海面上大一个量级．The characteristics of the atmospheric front have been investigated for a long time and their synoptic scale features have been studied widely by many meteorologists. However knowledge about the wind and temperature field near the ground of the front is not sufficient because the data about the structure of the PBL of a front are usually lacking. Recently, the data observed at meteorological towers and TV towers provide the possibility to research the structure of the front near the ground and the characteriStiCs of the front during its passage. Some papers have been published to date. In this paper,we shall use the gradient observation data collected at Beijing meteotological tower tO study some characteristies of the front near the ground and the PBL Structure during thepassage of night dry cold fronts.Here we analyze two cases of the forming process o(severe wind after the fronts. The results show that in North China, it is not certain that wind speed increases instantly during the passage of the main front, the increase of the wind speed may be postponed for several or even 20 hours after the front has passed. The analysis in the time-height cross-section shows that there is a temperature increase due to. sinking after the passage of the front and this results in the formation of an inversion. The inversion layer falls down inhomogeneously, as a result, the density current appears along a horizontal direction in thePBL, at the sametime the momentum accumulated on the top of the inversion transfers downward, this enables the wind speed near the ground to increase gradually with the characteristics of a gust. In the time-height cross-section the potential temperature field sampled every 20 seconds is analyzed. It is found that the front surface is approximatety perpendicular to the ground, in agreement with Shapiro et al (1984). The vertical velocity near the front surface is very strong. It may attain an order of magnitude about several meters per second, muchlarger than that in the region far from the front r

关 键 词：地面冷锋 边界层结构 湍流 风 锋面 

分 类 号：P425[天文地球—大气科学及气象学]