塔克拉玛干沙漠南缘戈壁下垫面辐射平衡与地表反照率特征

Radiation balance and surface albedo characteristics of the gobi underlying surface in the southern margin of the Taklimakan Desert

戈壁是荒漠地区主要的地表形式之一,这种下垫面特征与沙漠下垫面有较大差异,因此对于沙漠地区戈壁下垫面辐射平衡特征的研究十分有必要。利用中日沙尘暴合作项目(ADEC)塔克拉玛干沙漠南缘策勒戈壁观测站连续观测数据,分析了策勒戈壁站地表辐射平衡各分量全年、各季节与特殊天气下的日变化特征,以期为塔克拉玛干沙漠地-气系统能量交换提供更加具体的参数。结果表明:(1)策勒戈壁站各辐射分量最大值除向上短波辐射出现在1月外,其余各分量均出现在7月。(2)季节尺度上,各分量季节日变化最大峰值出现季节不一致,向下短波辐射和向上短波辐射最大峰值出现在春季,向下长波辐射、向上长波辐射和净辐射最大峰值出现在夏季。(3)不同天气下,各季节晴天各辐射分量均呈现平滑的变化趋势,多云、阴天、降雨期间各分量变化不规则,降雨和降雪天气向下长波辐射和向上长波辐射明显高于其余各分量。(4)地表反照率年均值为0.32,其中冬季降雪导致地表反照率远高于其他季节,各季节的次序表现为:冬季、春季、秋季、夏季。而反照率的日变化受太阳高度角影响,晴天呈现出平滑的“U”型,其他天气变化不规则。

The gobi,a prominent terrain feature in desert regions,exhibits surface characteristics markedly distinct from those of typical desert terrains.Therefore,it is imperative to investigate the radiation balance properties of the gobi’s surface in desert environments to enhance the accuracy of parameters used in land-atmosphere energy exchange models,particularly in the Taklimakan Desert.Utilizing continuous observational data from the Qira gobi station,situated on the southern periphery of the Taklimakan Desert as part of the China-Japan Sand and Dust Storm Cooperation Project(ADEC),this study examines the diurnal variations in the components of surface radiation balance at the Qira gobi station throughout the year,across different seasons,and under various weather conditions.The findings indicate that:(1)The peak values for radiation components at the Qira gobi station are typically observed in July,with the exception of upward shortwave radiation,which peaks in January.(2)The diurnal variation maxima for downward and upward shortwave radiation are recorded in spring,whereas the peak values for downward longwave radiation,upward longwave radiation,and net radiation are noted in summer.(3)During sunny days,the radiation components exhibit a consistent trend across seasons,whereas under cloudy,overcast,and rainy conditions,their variations are erratic.Specifically,during precipitation events,both downward and upward longwave radiations significantly surpass the levels of other components.(4)The annual average surface albedo is calculated at 0.32.Notably,the albedo increases substantially during winter owing to snow cover,with the seasonal sequence from highest to lowest being winter,spring,autumn,and summer.The diurnal albedo variation,influenced by the solar zenith angle,forms a smooth“U”shape on clear days,whereas it fluctuates irregularly under different weather conditions.