内蒙古半干旱草原沙尘天气对近地层微气象学特征影响分析

利用锡林浩特国家气候观象台2011年4-5月近地层微气象、地表辐射和湍流通量观测数据,对比分析了内蒙古典型半干旱草原下垫面在晴天、扬沙和沙尘暴天气下各气象要素、地表辐射分量和能量平衡的变化特征。对于半干旱草原区,地面风速越大沙尘天气越强；沙尘过程开始前地面空气较暖,开始后地面空气转为相对较冷的状态；沙尘气溶胶含量越高,5 cm地温日变化趋势越弱,在沙尘过程中5 cm地温值越小。沙尘气溶胶含量越高,太阳总辐射越弱,大气长波辐射越强；地表反射辐射与总辐射有相同的日变化特征；沙尘气溶胶白天使净辐射值减小,夜间使净辐射值增大。沙尘天气直接辐射衰减非常明显,而且散射辐射在总辐射中占很大的比重。沙尘气溶胶对紫外辐射的削弱很强,并且沙尘含量越高,对紫外辐射的削弱越强。沙尘气溶胶的辐射强迫作用对地表能量平衡产生影响,使向上的感热和潜热输送减弱,使向上的土壤热通量增强或向下的土壤热通量减弱。

Impact of Sand-dust Weather on Micrometeorological Characteristics in Semi-arid Grassland of Inner Mongolia

Diurnal variations of micrometeorological factors,surface radiation and energy budget on typical semi-arid grassland in Inner Mongolia under different weather conditions(clear day,blowing-sand day and sandstorm day) were analyzed based on turbulent flux,surface radiation and meteorological data obtained in April and May of 2011 at Xilinhot National Climatological Observatory in Inner Mongolia.The surface temperature decreased a lot under dust weather although it was warm before dust process.The higher wind speed brought about stronger dust process,and the ground temperature at 5 cm below decreased more under higher dust aerosol content.At higher dust aerosol content,the total radiation decreased more significantly but atmospheric long-wave radiation increased more significantly during dust process.The diurnal variation characteristics of ground reflective radiation and total radiation were the same.Net radiation decreased at daytime but increased in nighttime under influence of dust aerosol.The direct radiation and ultraviolet radiation(UV) declined sharply under high aerosol content.On dust day,the ratio of scatter radiation to total radiation was very high.Radiation forcing of dust aerosols also affected surface energy balance by decreasing upward sensible/latent heat transport and downward soil heat flux and increasing upward soil heat flux.