陇中黄土高原夏季地表能量平衡观测研究

Experimental Study on Surface Energy Balance over Loess Plateau of Middle Part Gansu in Summer

利用2003年6～8月的实际观测资料,分析了陇中黄土高原夏季地表通量特征。在春小麦下垫面,无论晴天或阴天,能量主要消耗于农田蒸散。在裸地下垫面各能量通量表现出同样的变化特征,但由于降雨量的增加,导致潜热占净辐射的比例比春小麦地的还高。在晴天或阴天地气之间能量传输引起土壤温度变化的深度,主要出现50cm以上,其日变化均呈现准正弦曲线形式,50cm以下的土壤温度不存在日变化。在半干旱区云和降水对地表辐射和能量平衡造成的影响不容忽视。波文比在日出以后逐渐增大,到正午达最大值;春小麦下垫面时的波文比大于裸地时的值,两者的极值分别是1.01和0.75。

The surface energy flux characteristic of Loess Plateau in middle part of Gansu is analyzed based on the experimental energy flux data observed over Dingxi Arid Meteorology and Ecological Environment Experimental Stations in June～August 2003. The result shows that the net radiation is mainly used up field evapotranspiration either in spring wheat field or in bare field on fine or cloudy days, which lead to the rate of latent flux to net radiation is higher at bare field than that at spring wheat one because of the rainfall increasing. The diurnal temperature variations of the surface and soil show the approximately sine curve on clear and cloudy days either at the surface or 5 cm and 10 cm depths, but the anti-phase variation on the weak extent at 20 cm depths, even no diurnal variation under 50 cm. Furthermore, the cloud and precipitation can bring about great influence on surface radiation and energy balance in semi-arid region. The Bowen rate is increasing after sunrise and the maximum value occurs at midday time and under zero with large fluctuation during night. Meanwhile the Bowen rate in spring wheat field is bigger than one in bare one and the both maximum values are 1.01 and 0.75 respectively.