青藏高原地面有效辐射变化及其对表层土温的影响

Variations of Surface Effective Radiation and Its Effect on Superficial Ground Temperatures on Tibetan Plateau

利用青藏高原格尔木、狮泉河、昌都日射站及中国科学院冰冻圈观测研究站的观测资料,分析了高原有效辐射的变化,在此基础上结合土壤温度资料讨论了高原北部有效辐射的变化对表层土壤热状况的影响.结果显示:1)青藏高原有效辐射变化因所处的区域不同而异,高原东北部、西部及高原腹地有效辐射总体呈减小的趋势,高原东南部有效辐射呈增大的趋势;2)有效辐射对冻结期间负积温的形成及持续时间影响较大,冻结期间负积温随地面有效辐射的减小而升高;3)有效辐射与地表融冻强度之间呈反相关,与融冻强度滞后两年的反相关更显著;4)青藏高原F/Q值大于地表反照率(Rk/Q),二者的作用均使地表失去能量而降温,总体上F/Q对地表的降温效应要大于Rk/Q.

Effective radiation,an important expenditure in the surface energy exchange,is quite significant to the studies of the physical processes of surface radiation balance,underlying surface thermal condition and energy exchange between land and atmosphere,etc.In this paper,using the observation data from the Cryosphere Research Station of Chinese Academy of Sciences and the solar radiation stations in Golmud,Shiquanhe and Qamdo on the Tibetan Plateau,the characteristics of effective radiation on the plateau were analyzed.Further more,combining with the data of ground temperature,the impact of effective radiation on thermal condition of superficial ground was discussed.It is found that： 1） the distribution of effective radiation is different from place to place,showing a decreasing tendency in the northeast,west and hinterland of the plateau,but an increasing tendency in the southeastern plateau;2） effective radiation plays a great role in the formation and duration of the cumulative temperature below 0 ℃ during the freezing process;3） effective radiation shows a negative correlation with the surface freezing-thawing intensity（FTI）,and more notable with the FTI of two-year lag;4） effective radiation takes more share in the global solar radiation than reflected radiation.It occupies the first of the expenditure part in the radiation balance.The effects of F/Q and R-k/Q both make land surface lose energy and lower temperature.Overall the cooling effect of F/Q is more intensively than Rk/Q.