Bai Zhongyuan, Tetsuo Ohata, Keiji Higuchi
In order to advancing studies on the relationship between the radiation energy transfer and topographical factors, the differences in solar radiation due to the influence of direction and angle of slope and mountain screening on solar radiation were calculated for east-branch of Glacier No. 1 and a Glacier-free Cirque at the headwater of Urumqi River, Tainshan Mountains. According to computed data of the different directions and inclination of glacier and cirque, slope factor of solar radiation and the sunrise and sunset at various solar declinations under influence of shadowing effect of surrounding mountains at 29 points, the difference of energy reductions in solar radiation owing to northerly or southerly exposure and screening effect are small in whole ablation period about 31.5% and 29.5%. But in the period of shorter solar path the difference becomes more important. In the glacier area, the loss in energy is 40.3% at the equinox, and even reaches 50.1% in early winter (solar declination is-10?). Meanwhile in the glacier-free cirque area during the same period, the loss in energy is only 19.5% and 13.9% respectively. The mean loss in energy are 40.6% and 21.0% in glacier area and glacier-free cirque area during three periods and provides various solar radiation energy condition for glacial nourishment.On the basis of spatial variations studies of mean value of the insolation duration and albedo during summer ablation period (from June to August, for a solar declination of 20), the fields of radiation energy for components of the radiation balance of physical surface of east-branch of Glacier No. 1 under clear and slightly clouded weather are presented, using observed data and regression equations in this region and mountain glacier of West China. The spatial distribution charts of above factors obviously reflect thecontrol effects of topographic condition and albedo on the mean daily sum in fields of radiation energy during the summer ablation period, and has an obvious zonal distribution regularity with gradually decreases from northwestern flank to the southastern flank. The vertical gradients of global radiation and effective radiation in the glacierized region under investigations (from 3775 mm to 4200 m) equal to 14.52 Wm-2/100 m and 2.77 Wm2/100 m respectively. Calculations presented this paper show that exposure and screening effect are very important to the maintenance of glaciers in particular valleys, and explain why there are no glaciers in certain cirque or valleys at same altitudes.
