青藏高原冬季降雪对地面净辐射的影响

过去的研究结果指出，冬季青藏高原地面净辐射场是一个由地理因子决定的基本场叠加上一个降雪后地面积雪区造成的扰动场组成，为定量研究冬季青藏高原降对地面净辐射的扰动幅度，利用作者已经建立的冬季青藏高原后地面反射率与降雪降雪面无（有）积雪时计算地面净辐射的公式，计算了不同强度降雪后地面净辐射日总量及其变化。

THE INFLUENCE OF SNOW ON THE SURFACE NET RADIATION OVER QINGHAI-XIZANG PLATEAU IN WINTER

The results of the previous studies show that the geographic distribution of surface net radiation over the Qinghai-Xizang Plateau in winter consist of a basic pattern determined by the geographic conditions and a perturbation pattern caused by snow._In order to study quantitatively the perturbations of surface net radiation caused by snow,the daily totals of surface net radiation and their variations after snow with different snowfall were calculated by use of the relationship between the albedo after snow and the snowfall,and the empirical formulae for calculating surface net radiation in cases of snowcover.The results show that the duration of negative surface net radiation after snow is determined mainly by the snowfall,6 days of the duration of negative surface net radiation may occur when snowfall is 2.0mm,but 20 days when snowfall is 10.0mm.The sunshine duration affects strongly the magnitude of surface net radiation,the absolute value of the totals of net radiation in case of the clear day ( S 1=0.9) is greater than that in cloudy day ( S 1=0.2) after snow with the same snowfall.In winter,the surface net radiation is positive in Nagqu if none of snowcover,the monthly totals of surface net radiation in December is about 2.52 2.88MJ/m 2.But the totals of the negative surface radiation budget after snow with the snowfall 10.0mm is -2.62MJ/m 2,the absolute value of which is nearly equal to the monthly totals of the positive surface radiation budget (3.19MJ/m 2) in Lhasa.