西藏高原斜压对流边界层风、温、湿廓线特征

利用1998年夏季第2次青藏高原大气科学试验当雄观测站的边界层观测资料以及拉萨、改则和武汉等地探空资料,分析讨论西藏高原斜压对流边界层风、温、湿廓线的特征. 研究结果表明,高原地区白天对流边界层发展可高达2200m,显著超过中纬度平原地区和海面上对流边界层高度. 高原对流边界层中温度廓线具有较好的混合特征,湿度廓线有时在某一高度上出现湿度极大值. 高原对流边界层内热量和水汽收支分析表明,水平平流作用对边界层结构具有重要作用. 在对流边界层中平均风速垂直分布存在风切变现象. 水平温度梯度形成较强的斜压性是形成边界层风切变的主要原因.

THE CHARACTERISTICS OF THE PROFILES FOR WIND, TEMPERATURE AND HUMIDITY IN THE BAROCLINIC CONVECTIVE BOUNDARY LAYER ON XIZANG PLATEAU

The characteristics of the profiles for wind,temperature and humidity in the baroclinic convective boundary layer on Xizang plateau were analyzed and discussed based on the observed data of Damxung boundary layer station and the radiosounding data at Lhasa,Gerze and Wuhan during the second field experiment of atmospheric sciences on Xizang plateau. The results illustrate that the convective boundary layer at daytime on the plateau could be developed strongly with a height of 2200m,which is distinctly higher than that over plain and ocean in middle latitude. The temperature profile in the plateau convective boundary layer has the well mixed characteristics,while the maximum value of humidity appears sometimes at certain level in the humidity profile. The budget analyses of heat and water vapour in the plateau convective boundary layer shows that the horizontal advection has important effect on the structures of boundary layer. There exists the wind shear in the vertical distribution of the average wind speed in the convective boundary layer. The baroclinity formed by the horizontal temperature gradient is the main reason for the formation of the wind shear.