白洋淀水陆不均匀地区能量平衡特征分析

Energy Budget over the Water-Land Heterogeneous Surface in Baiyangdian Region

应用2005年9月在河北白洋淀地区进行的大气边界层综合观测实验资料,对水陆不均匀地表条件下的白洋淀地区陆地的能量平衡特征进行了分析。结果表明：（1）该地区存在能量不闭合现象。涡动相关法得到的感热、潜热之和仅为有效能的75%,其中涡动相关法得到的潜热通量为Bowen比法得到的潜热通量的70%,而涡动相关法得到的感热通量为Bowen比法得到的感热通量的77%。（2）地表潜热通量和感热通量随着净辐射的变化而变化。但潜热通量明显比感热通量大,净辐射主要消耗于地表的水汽蒸发。（3）该地区白天的Bowen比平均在-0.4～0.4之间,总体平均为0.131。受天气条件影响较大,有明显的日变化,午后15：00以后近地面层会出现逆温,Bowen比变为负值。（4）能量闭合程度有一定的日变化,随着太阳高度角的增大而增大。

The phenomenon of energy imbalance over heterogeneous surface is very significant. In this paper, a comprehensive field experiment of atmospheric boundary layer （ABL） over the water- land heterogeneous surface was briefly introduced-- ＂Baiyangdian Field Experiment for Heterogeneous Boundary Layer＂. The experiment was performed in Baiyangdian area of North China during 8 - 27 September 2005. Some characteristics of energy budget over this water- land heterogeneous surface are analyzed. The results show that （1） there exists energy imbalance in Baiyangdian region. The sum of sensible heat flux and latent heat flux measured by the Eddy Correlation （EC） method is about 75% of the available energy, while the latent heat flux measured by the EC method is about 70% of that measured by the Bowen Ratio （BR） method, and the sensible heat flux measured by the EC method is about 77% of that by the BR method. （2） The surface latent heat flux and sensible heat flux vary with the net radiation energy. But the latent heat flux is larger than sensible heat flux, which means that the net radiation is consumed for evaporating water from surface. （3） The value of daytime Bowen ratio β is between --0. 4 and 0. 4, with mean value 0. 131, which is influenced greatly by weather condition. The diurnal variation of β is obvious, and the value of β becomes minus when the temperature inversion appears over surface after 1500 LST. （4） The energy balance closure changes diurnally, and increases with the solar altitude. Also, a few remarks and some discussion about the mechanism of energy imbalance over heterogeneous surfaces are given at the end of this paper.