夏季青藏高原热力场和环流场的诊断分析——Ⅱ:环流场的主要特征及其大型垂直环流场

本文使用经过青藏高原气象科学实验测站观测资料订正过的欧洲中心FGGE-Ⅲb资料,对1979年7月月平均进行分析,计算了垂直速度、散度、垂直剖面函数和速度势函数等物理量以及上升气流轨迹,给出了夏季高原主体地区环流场的主要特征和详细的高原地区不同经纬度剖面垂直环流场的特征和分布. 配合夏季高原高层强大稳定的反气旋高压带,高原主体地区为整层上升气流区,但ω场有东西两个上升中心,它们是两个对流活动上升中心,两部的中心位于狮泉河和改则之间偏北的地区,东部的位于那曲一带. 本文给出了高原地区三个主要的经向环流圈(南北两侧下沉的小环流圈、跨赤道的季风环流圈)的经度位置和高原地区与西太平洋之间发生遥相关的主要纬度位置,发现在跨赤道的季风环流圈中,在赤道以南的下沉气流主要来自高原与15°N之间,从高原上升的气流仅在对流层上部(200hPa左右)跨过赤道.从高原西部上升的气流往往从非洲至印度尼西亚一带跨过赤道,而从高原东部及其东侧我国大陆上升的气流往往下沉在太平洋和北大西洋地区.

The Influence of the Tibetan Plateau on the Thermaland Circulation Fields over East Asia in summerII: Main Features of the Local Circulation Fieldsand the Large-scale Vertical Circulation Fields

Based on the monthly averaged fields in July 1979 of the Revised ECMWF FGGE Level III b data which has been corrected by the Tibetan Platean Meteorology Experiments data. the vertical velocity fields, the divergence fields , the stream function fields on the vertical sections and the ascending air trajectories etc . are analysed and the major features of the circulation fields on the Tibetan Plateau, the distributions of the vertical circulation fields on the different meridian and zonal sections crossing the plateau are showed .There is a strong and stable anticyclone high belt at the upper air, accompanying ascending air filled the entire troposphere on the main part of the Tibetan Plateau, M oreover, we discovered yet that there are two convective activity ascending centers on the plateau . One is situated in the area of the Shiquanhe and Gaize , the other is situafed Naqu region .The longitudinal positions of three prime meridian circulation cells , i .e . two smaller circulation cells which descend at the south and north sides of the plateau and the cross-equatorial monsoon circulation cells, and the main latitudinal positions of the teleconnection between the Tibetan Plateau and the western Pacific are presented. We found that only some- of cross-equatorial monsoon descending currents are come from the Tibetan Plateau which cross the equator only at the upper levels of troposphere (about 200 hPa X and most of the currents are ascend on the ocean south of the plateau .The 3-D trajectory figure showes that the current upward from western and eastern part of the Tibetan Plateau are very difference . The former in general crosses the equator with the positions from Africa to Indoneaia. The latter showes that the eastern Tibetan Plateau and the China continent have direct circulations circles with the eastern Pacific and the northern Atlantic , so that there are some teleconnection phenomenons between them .