陇中黄土高原冬季地表辐射和能量平衡特征

THE CHARACTERISTIC OF SURFACE RADIATION AND ENERGY BALANCE IN LOESS PLATEAU OF MIDDLE PART GANSU IN WINTER

利用定西试验基地2003年12月至2004年2月获取的地气相互作用观测资料,分析了陇中黄土高原冬季典型天气(晴天、阴天及雪天)和平均状况下的地表辐射能量平衡和土壤温度等微气象特征的日变化规律.结果表明,在典型天气间微气象特征有较大差异,但冬季的平均特征与晴天比较接近,云和降雪的扰动影响有限.冬季地表能量平衡以感热输送为主,土壤热通量为辅,且普遍存在不平衡现象.冬季初的2/3时段净辐射及土壤热通量日总量基本为负值,之后的1/3时段为正值,冬季地面加热场为热源.冬季土壤温度在地表及20 cm土壤层存在日变化,30 cm及以下土壤温度日变化很小.冬季地表日平均反射率基本在0.20～0.25之间变化,平均值为0.22.

By using the land-atmosphere interaction measured data observed over Dingxi Arid Meteorology and Ecological Environment Experimental Station, luring December 2003 to February 2004, the characteristics of the daily variations of the surface radiation budget, energy balance, and soil temperature under different types of synoptic conditions （including a clear day, a cloud day and a snow day） and averaged conditions are analysed. The comparison of micrometeorological characteristics under the three types of synoptic conditions shows that there is much different among features of radiation and energy budget under different synoptic conditions, the characteristics of the averaged daily variation in winter is very close to ones under the condition of a clear day because the influence of cloud and snow are limited, In winter, the sensible heat flux plays a leading role, and the soil heat flux depends on it. However, there is an large imbalance in surface flux measurement, The daily value of net radiaton and soil heat flux is negative in 2/3 times after winter comes, and it becomes positive in the rest time, so the surface heating field is heat source in winter. The diurnal variation of the soil temperature is just in the upper 20cm layer soil. The soil temperature below 30cm has very litter diurnal variation. The diurnal average of surface albedo is varied between 0.20 and 0.25, and the mean of diurnal surface albedo is 0.22.