黄土高原蒸发力的计算和应用——兼谈改善生态环境的途径

蒸发力是气候学上的一个重要特征量。在水利工程设计、灌溉定额的制定、农林牧的合理布局需要以蒸发力资料为依据。彭曼公式具有较可靠的物理基础和计算精度较高的优点,在国际上得到了广泛的应用。我国某些学者在运用该公式时,未考虑海拔高度对蒸发力的影响,因此在高海拔地区应用彭曼公式会产生较大的误差。 本文应用高度订正后的彭曼公式:计算了黄土高原地区的蒸发力。 森林减弱了近地层风速,降低了该地区的蒸发力,农田水分状况得到了改善。

THE CALCULATION AND USE OF THE POTENTIAL EVAPOTRANSPIRATION FROM LOESS PLATEAU,——ABOUT THE WAYS OF ECOLOGICAL ENVIRONMENT REMEDY

The potential evapotranspiration is an important characteristic value in climatology. The water conservancy project, the planning of irrigation requirement and the rational distribution of agriculture, forest and animal husbandry, all are based on the potential evapotranspiration. The formula of Penman has the advantages of more reliable physical basis and higher computed precision. It has been widely applied by the countries in the world. But when it was applied by the scholars in China, they did not considered the impact of sea level elevation on the potential evapotranspiration. When they use the Penman's formula in high elevation, errors should be appeared.Considered the elevation, this paper corrected the formula of Panman as follows:and the potential evapotranspiration from Loess Plateau was calculated.The formula of Penman may be divided into two parts: the radiation component and the dynamic component of the potential evapotranspiration. The energy of the radiation component is provided by the solar radiation and the dynamic component is related to the wind speed (u2) and the saturation deficit (ea-ed), i.e. the smaller the wind speed and saturation deficit, the larger of the dynamic component of the potential evapotranspiration.Wind speed near the ground was decelerated by the forest and consquently decreased the potential evapotranspiration. Then the water state of the fields was remedy.