雅鲁藏布江下游典型河谷地带辐射收支及反照率特征研究

Surface radiation budget and albedo characteristics in typical valley areas of the lower reaches of the Brahmaputra River

摘要:

利用雅鲁藏布江下游典型河谷中林芝机场2014年的地表辐射数据，结合晴空指数识别的晴阴天，分析该地地表辐射分量、地表反照率逐月变化及四季典型晴天、阴天条件下的日变化特征。结果表明：（1）地表辐射分量的月均值变化显示，除了短波辐射外，其余分量均呈现明显的单峰月变化。地表长波辐射、大气长波辐射、净辐射月均最大值出现在6月至8月，分别为414.1 W/m2、371.2 W/m2和151.4W/m2。反射短波辐射的月均值最大值出现在3月，为98.4 W/m2。太阳总辐射由于夏季云量较多，且阴天天数明显高于其余14年的夏季平均天数，月均最大值出现在10月为560.3 W/m2。（2）在典型晴天中，辐射分量的日变化呈现出光滑的单峰型，而在阴天则表现为不规则的多峰型。与晴天相比，阴天表现出大气长波辐射增强，白天其他各辐射强度显著减弱。特别是地表长波辐射和净辐射在夜间明显增强。（3）地表反照率月平均日变化表现为先减小后增加的“U”型曲线，季节变化表现为冬季＞秋季＞春季＞夏季，最大和最小月均值分别出现在2月和6月，为0.25和0.14。

Abstract:

Utilizing the surface radiation data from Nyingchi Airport in the typical river valley of the lower reaches of the Brahmaputra River in 2014, and combining it with the clear-sky index to identify sunny and cloudy days, this study analyzed the monthly variations of surface radiation components, surface albedo, and diurnal variations under typical sunny and cloudy conditions in different seasons at that location. The results show that: (1) The monthly average variations in the components of surface radiation show that, except for shortwave radiation, all other components exhibit distinct unimodal monthly changes. The monthly maximum averages of surface longwave radiation, atmospheric longwave radiation, and net radiation occur from June to August, at 414.1 W/m2, 371.2 W/m2, and 151.4 W/m2 respectively. The monthly average maximum of reflected shortwave radiation occurs in March, at 98.4 W/m2. Due to the higher cloud cover during the summer months and a significantly higher number of overcast days compared to the average for the other 14 years, the monthly maximum of total solar radiation occurs in October, at 560.3 W/m2 .(2) The diurnal variations of radiation components on typical sunny days exhibit a smooth single-peak shape, while on cloudy days, they show an irregular multi-peak shape. Compared to sunny days, cloudy days show enhanced atmospheric longwave radiation, which decreases in the afternoon due to local circulations. Other radiation intensities significantly weaken during the day, with surface longwave radiation and net radiation showing a notable increase at night.(3) The monthly average diurnal variation of surface albedo presents a "U"-shaped curve, decreasing first and then increasing. The seasonal variation follows the order of winter > autumn > spring > summer, with the maximum and minimum monthly averages occurring in February and June, at 0.25 and 0.14, respectively.