中天山地区草地地表辐射收支演变规律

地表辐射对研究地表能量平衡及气候形成机制具有重要意义。利用中天山乌拉斯台地区陆气相互作用观测站2018年5月至2019年4月地表辐射数据，分析了中天山草地不同时间尺度和不同天气条件下的地表辐射与反照率变化特征。结果表明：(1)地表辐射月平均日变化除大气长波辐射较弱外，其余分量均呈单峰型，极值大小及时间存在差异，太阳总辐射与净辐射最大日峰值均出现在6月，为920.9与603.3 W/m~2,大气与地表长波辐射分别出现在7月和8月，为327.5 W/m~2与471.7 W/m~2,而反射短波辐射则出现在2月，为520.6 W/m~2。(2)太阳总辐射、反射短波辐射、大气与地表长波辐射年曝辐量分别为6860.62、2101.72、7171.25、10089.69 MJ/m~2;就季节变化而言，反射短波辐射曝辐量在冬季明显高于其它季节，其它分量则均表现为夏季>春季>秋季>冬季。(3)不同月份地表反照率日变化均呈“U”型曲线，年均值为0.393,最大与最小月均值分别出现在12月与8月，为0.760与0.217。这种变化体现在季节上则为冬季>秋季>春季>夏季。(...

The rule of grassland surface radiation budget in the middle of Tianshan Mountains

Surface radiation budget is of great significance to the research for the surface energy balance and the mechanism of climate formation and change. The variation characteristics of surface radiation budget and surface albedo at different time scales and in different weather conditions for Ulastai grassland area in the middle of Tianshan Mountains were analyzed by using observation data in the middle of Tianshan Mountains Land-Atmosphere Interaction Observation Station from May 2018 to April 2019. The results demonstrated that:(1) the monthly mean diurnal variation curves of surface radiation components, except that the curve of downward long-wave radiation was weak, were all in unimodal type. The extreme values of surface radiation components appeared at different times and were unequal. The extreme value of the diurnal curves for both of the downward short-wave radiation and the surface net radiation appeared in June, which were 920.9 W/m²and 603.3 W/m². The extreme values of the diurnal curves for both of downward and upward long-wave radiation appeared in July and August, which were 327.5 W/m² and 471.7 W/m². But the extreme value of the diurnal curve for upward short-wave radiation appeared in February, which was 520.6 W/m². (2) The annual total values of downward short-wave radiation, upward short-wave radiation, downward long-wave radiation and upward long-wave radiation were 6860.62 MJ/m², 2101.72 MJ/m², 7171.25 MJ/m², and 10089.69 MJ/m². In terms of seasonal variations for surface radiation components, the monthly total value of upward short-wave radiation was significantly higher in winter than in other seasons, while the monthly total values of other surface radiation components ranked as summer > spring > autumn > winter. (3) The monthly mean diurnal variations of surface albedo were all in U-shaped curves in different months. The average annual value of surface albedo was 0.393, and the extreme and minimum monthly mean values of surface albedo appeared in December and August, which were 0.760 and 0.217, respectively. In terms of seasonal variations for the surface albedo, the seasonal mean values of surface albedo ranked as winter > autumn > spring > summer. (4) The diurnal variation curves of surface radiation components were more smooth on clear day than cloudy and rainy days. The responses of downward short-wave radiation and upward long-wave radiation to precipitation were weakened, while downward long-wave radiation was enhanced. The response of upward short-wave radiation to precipitation was consistent with surface albedo, which was weakened and enhanced in rainy days and after snowfall, respectively.