黄土高原中部典型台塬区冬季微气象特征研究

Study of Micrometeorological Characteristic in Typical Terrace Region of Middle Loess Plateau in Winter

利用黄土高原中部庆阳观测站冬季的观测资料,分析了黄土高原台塬区微气象特征。研究表明,黄土高原中部冬季晴天辐射各分量的值几乎比夏季的小一半。09:00～17:00,地面给大气加热,在17:00至次日09:00,大气给地表加热。平均辐射与晴天时更接近。无论是晴天还是平均气候状况,冬季感热在地表能量中都占有很大比重,几乎占到净辐射值的一半;潜热峰值只有感热峰值的1/4左右,土壤热通量介于感热和潜热之间。冬季夜间近地层的湍流交换十分微弱,在一天中的2/3时间里,大气给地表传递热量。在无降水时段,地表反照率平均为0.22,降雪的影响使地表反照率的平均值为0.28,增大了约30%。地表反照率恢复到一个新的准平衡态长达7天。降雪过程对地表反照率的影响是一个非常复杂的过程,这也是地表反照率难以准确参数化的原因之一。

The micrometeorological characteristics in terrace region of Loess Plateau in winter are analyzed using the observation data from LOPEX（Experimental Study of Land Surface Processes in Chinese Loess Plateau）.The results show that each component of radiation fluxes on clear day in winter has only half as much as that in summer.The surface is heated by atmosphere at most of time（from 17：00 to 09：00 of the next day）.The average radiation is close to that on clear day.The sensible heat flux in winter occupy large proportion in surface energy which is an half of net radiation whether on typical clear day or average condition.The ratio of the latent heat flux is only 25% of the sensible heat flux and the soil heat flux is between the sensible heat flux and the latent flux.The turbulent exchange at nighttime in winter is very weak.The heat is transferred from atmosphere to surface in two third times of a day.Average value of albedo is 0.22 during the non-precipitation period time and that is 0.28,which is almost increasing 30%during the snowfall process.It needs 7 days when albedo restores to new quasi-equilibrium.The effect of the snowfall on albedo is very complicated,which is one of reasons that are difficult to predict albedo.