河西戈壁地区不同天气背景下微气象状况的初步分析

A PRELIMINARY ANALYSIS OF MICROMETEOROLOGICAL CHARACTERS UNDER DIFFERENT CONDITIONS OF METEOROLOGY

对黑河计划ＩＯＰ期间在化音戈壁站观测的湍流脉动场资料及有关梯度资料进行了分析，得到了湍流脉动强度、湍流感热、潜热通量和温、湿梯度的若干特征。无量纲脉动强度的变化趋势与经典关系基本一致，但在量上稍有差异；一般的晴天情况下，感热大于潜热，湿度场以逆湿为主；不过感热和潜热的比例关系和湿度梯度均随天气状况而变；在每一个降水过程中湍流通量特征可以分为四个阶段，各个阶段的感热和潜热均有较大差异；降水发生过后。

In this paper, we have analysed the data of the turbulence and gradient of tempera ture and humidity, which were observed at Huayin Station in Gobi area during IOP -2、3、4 periods of HEIFE Project, to obtain some characteristics of turbulence intensities. The tendency of the nondimensional turbulence intensities is mainly in agreement with the results obtained over other underlying surfaces, but there is some qualitative difference between them. And using the data of turbulent fluxes observed at Huayin Station in Gobi area during IOP-2 period of HEIFE Project, we have studied the difference between the characteristics of the eddy sensible heat fluxes,the eddy latent heat fluxes and the gradients of temperature and humidity on a fine day, during the period from August 10 to 17, 1991 when there was influence of rainfall on micrometeorology. In a generally fine day, the sensible heat fluxes are much larger than the latent heat fluxes, and the main characteristics of the humidity fields belong with the inverse humidity. But both the ratio of sensible heat flux to latent heat flux, and the gradient of potential temperature and humidity change with the different conditions of weather. During the rainfall process, the characteristics of turbulent flux can be divided into four periods, and there are different values of the sensible and latent heat fluxes during four different periods. During the first period, when it is raining, the raindrops weaken the solar radiation flux arriving at surface to very samall value, so both the sensible heat flux and the latent heat flux become a little. During the second period, that is the first day after the rainfall, the latent heat flux increases sharply but the sensible heat flux increses slowly, becuause the solar radiant flux arriving at surface has reaturned to normal value of a fine day and the surface soil is still damp. During the third period, that is the second day and the third day after the rainfall, the sesible heat flux still increases but the latent heat flux decreases by degrees, because the surface soil has become drier than the early period. During the fourth period, that is the fourth day ad farther days after the rainfall, the surface soil moisture mainly returns to that of normal fine days, so the sensible heat flux on the surface energy budget becomes in majority gradually but the latent heat flux becomes a little or may be neglected. It needs four days when the characteristics of the sensible and latent heat fluxes reutrn to those before rainfall.