黑河地区行星边界层大气的气候分析

CLIMATIC ANALYSES OF THE PLANETARY BOUNDARY LAYER ATMOSPHERE IN THE HEIHE REGION

分析指出:气温和比湿的季节变化基本上呈峰谷相当波型;各月气温和比湿的直减率分别小于和略大于自由大气的直减率。整层各月为准无辐散和弱有旋的西北气流,风速的季节变化在近地层也呈谷峰相当波型,其振幅随高度迅速增强,但位相恰与温、湿波型相反。张掖单站分时次的月平均资料分析表明,风向、风速和层结稳定度都有明显的气候日变化;当考虑湿度层结时,夏季7月19时的平均层结是真潜不稳定,其余季节和时次仍为稳定层结。扩展域边界层月平均温、湿、风场的分析指出,黑河地区近地层在1、4、10月基本上位在平浅温度槽区,而7月却处在纬向水平温度梯度矢端;该区比湿7月相对最高,而其余各月很低;全域近地层流场仅7月稍复杂点,黑河试验区位于弱辐合流场中,其余月份黑河地区边界层平均基本上为平直西北气流所控制。

In this paper, the climate characters of the temperature, humidity and wind fields on the planetary boundary layer (PBL) over the Heihe region and its neighbourhood have been analysed utilizing the multi-year monthly mean data at grided points and some sta tions of the area. The results indicate that the seasonal variations of the temperature and specific humidity on the PBL appear a waveform with basically equivalent value for the peak and valley; the lapse rates of the temperature and specific humidity on the PBL for each month are less and large than those on the free atmosphere, respectively. There is a northwest flow with quasi-nondivergence and weak rotation in the whole PBL. The seasonal variation of wind speed also appears a waveform with a equivalent value for the peak and valley in the surface layer, the wave amplitude increases rapidly with height, however, the phase is just contrary to the waveform of the temperature and specific humidity. The analyses of the monthly mean data at the Zhanye station for 07- and 19-hrs. (BLT) indicate that there is a pronounced climatically diurnal variation for the wind direction, wind speed and stratified stability. The monthly mean stratification only at 19(BLT) in July is true potential instability when the stratification of the temperature and humidity in the PBL was analysed at the same time, in the rest seasons and times are still stable stratification. The briefly analyses of monthly mean fields of the wind, temperature and specific humidity in the PBL of extension domain indicate that the surface layer of the Heihe region in the January, April, October is located at the shallow temperature trough area, however, the region in July is just located at the end of zonal temperature gradient vector; the specific humidity in July in the region is the a highest, the other months are very low; the streamlines on the surface layer in extension domain only in July are something complex, the surface layer over Heihe region is located a weak convergence flow field; the PBL over the Heihe region for rest months are basically controlled by the straight north west flow.