蒸发皿蒸发及能量变化过程的微气象观测研究

Study on Pan Evaporation and Energy Change Process by Micro-Meteorological Method

蒸发皿作为测量大气蒸发需求的仪器,在水文和气象台站广泛使用。为了深入认识蒸发皿蒸发量的物理意义,在中国西北干旱区设置了"内蒙古蒸发皿蒸发试验(IMPEEX)"。利用近地层微气象观测方法,基于能量平衡原理,对Class A、20 cm和E601B三种不同型号的蒸发皿蒸发过程进行精细观测,观测结果显示:三种蒸发皿蒸发量日变化之间存在显著差异,而这种差异主要是由蒸发皿水体与周围环境构成的非均匀性强度所控制;蒸发皿中水体越深,水温层结越显著;E601B蒸发皿水体与土壤之间的热通量约在±10 W·m-2之间波动,但日总通量几乎为0;典型晴天Class A蒸发皿水面反照率呈"U"型日变化,日平均值为0.087。蒸发皿水体能量平衡分析显示,太阳辐射和水体储热率是决定蒸发皿蒸发强度的主要能量分量,而水面感热、侧壁和底部热传导对蒸发皿蒸发量的贡献较小。

Pan is used as an instrument of measuring the evaporation demand of atmospheric,and is widely used in hydrological and meteorological stations. In order to deeply understand the physical significance of pan evaporation,a field experiment ＂Inner M ongolia Pan Evaporation Experiment（ IM PEEX） ＂is carried out in the arid region of northwest China. Based on the energy balance principle,the evaporation processes of Class A,20 cm and E601 B pans are measured minutely with micro-meteorological method. The observations results showthat the diurnal variations of three types of pans evaporation processes have significant differences owing to the non-uniformity intensity between water body of pan and the surrounding environment. Temperature stratification of water in the pan is increasing with the depth of water. The heat flux between E601 B pan water and around soil fluctuates between ±10 W ·m-2,and the sum of this flux is almost 0 at daily time scale. The albedo of water surface of Class A pan is displays ＂U ＂type at sunny days,and the daily averaged albedo is 0. 087. Energy balance of water of pans analysis shows that the solar radiation and water thermal storage rate are the main two components of energy which control the pan evaporation,the sensible heat flux at water surface and heat conduction through pan wall and bottom are subordinate components.