从能量平衡方程和热传导方程出发,引进"相对蒸散"和"相对干燥力",建立了用常规气象资料估算实际蒸散的理论模式。该模式避免了计算实际蒸散需首先计算可能蒸散这一过程,从而解决了由于采用不同的"可能蒸散"估算方法带来的误差。利用近30年的水文、气象等资料,在全国选择了九个有代表性的流域。对流域年实际蒸散量的模拟结果显示,除黄河流域部分年份外,可以将陆面年实际蒸散量的估算误差控制在10%以内。

Evaporation (Evapotranspiration) consumes much of the water and energy that is available on the ground of the earth and therefore influences all hydrological and most meteorological processes It also plays an important role for the water redistribution on the earth’s surface and is a major determinant of the amounts in water cycle Instruments can only measure evaporation in research context for small areas, which are subject to intensive studies Therefore, there is a strong need for reliable methods that can estimate actual evaporation and require only a few meteorological parameters which are readily and routinely obtainable at standard weather stations Based on energy balance equation and mass transfer equation, a general model to estimate actual evaporation from non saturated surfaces was introduced Making use of two concepts,"relative evaporation" and "relative drying power", a relationship was established to account for the departure from saturated conditions Using this model, the actual evaporation can be calculated without the need of potential evaporation estimation Furthermore, the model requires only a few meteorological parameters that are readily and routinely obtainable at standard weather stations Based on nearly 30 years of meteorological and hydrological data, in combined with GIS, nine representative river basins were selected Using the data of the selected river basins, the model was tested The results show that the actual evaporation rate can be estimated within an error of 10% in most area of China.