蒸发在地理环境研究中具有关键性作用。蒸发力的概念起初是随研究蒸发而提出来的,凡提到蒸发时,往往要提到蒸发力。但研究蒸发力的意义,远不只这一点。现在从事蒸发力研究的,不但有气象学家,水文学家,土壤和植被方面的专家,还有从事农业及生态系统研究的专家。我们则主要从自然地理的角度来探讨。

This paper consists of following 3 parts:1. discusion on the method and conception of Potential Evapotranspiration.2. calculation and distribution of the Potential Evapotranspiration in China.3. some problems on the Potential Evapotranspiration studies.The first part discusses different methods of measuring the evapotranspiration and suggests to distinguish different conceptions of Potential Evapotranspiration according to the condition under which they are measured or calculated. Four conceptions are identified: Normal Potential Evapotranspiration (NPE) under the condition of unlimited water supply, complete vegetation cover and surrounded with uniform large area; Climatic Potential Evapotranspiration (CPE) under the condition of unlimited water supply but without uniform vegetation; Pseudo-Potential Evapotranspiration (PPE) under the condition of limited water supply; and Local Potential Evapotranspiration (LPE) in a small area with unlimited water supply and surrounded with large area of arid or semiarid condition.In the second part, the H. L. Penman’s formula for calculating the Potential Evapotranspiration is applied and the Map of mean year’s Potential Evapotranspiration in China has been drawn.The third part deals with the orientation of the Potential Evapotranspiration studies. Two suggestions are emphasized: to improve the measuring instruments and to increase comprehensive studies.