天山乌鲁木齐河源冰川与空冰斗辐射气候的计算结果

Calculation Results of Radiational Climate in Glacierized Cirque and Glacier-free Cirque at the Headwater of Urumqi River in Tianshan Mountains

提要 在朝向、坡度和山体遮蔽度影响下,与水平面相比朝北冰川和朝南空冰斗在太阳偏角为15°,0°和-10°时的平均太阳辐射能量损失分别是40.6％和21.0％。1号冰川东支夏季消融期内自然冰雪面辐射场内辐射平衡各分量平均日总量值受地形因素和反射性能的控制而显示出由西北侧向东南侧逐渐降低的带状分布规律。晴朗少云天气下的总辐射和有效辐射的垂直梯度分别是14.52Wm^(-2)/100m和2.77Wm^(-2)/100m。

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 W ?m-2 / 100 m and 2.77 W ?m2/ 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.