根据20 cm 蒸发皿的几何尺寸和架设特征，对Penman蒸发公式中的辐射项Rn和储热项S进行修改，建立了20 cm蒸发皿蒸发模型。利用古浪非均匀近地层观测试验（GHUSLE）中连续14天观测的20 cm蒸发皿逐时蒸发数据对该模型进行验证。结果表明，该模型能够成功地模拟蒸发皿蒸发的日变化过程，模拟的日蒸发量均方根误差和平均相对误差分别为0.72 mm·d-1和6.7%。20 cm蒸发皿蒸发过程中太阳辐射项的贡献约占蒸发皿总体蒸发的1/3，空气动力项的贡献约占2/3。常规气象因子影响蒸发皿蒸发的敏感性试验表明，风速、空气湿度、太阳辐射和气温对蒸发皿蒸发的影响强度依次递减，其蒸发量随这4种气象因子的变化率分别为0.602，-0.590，0.528和0.370。
According to geometry dimensions and installation characteristic of the 20 cm pan, the evaporation model of 20 cm pan was built by modifying the radiation and thermal storage items in Penman formula. Following, the model was calibrated by the continuous 14-day hourly measurements which were from Gulang Heterogeneous Underlying Surface Layer Experiment (GHUSLE). The analysis results showed that the model could simulate the diurnal variation of pan evaporation. In addition, the results indicated that day performance of the model was good with a root-mean-square error of 0.72 mm·d-1 and a mean relative error ratio of 6.7%. The simulation analysis showed that the contributions of radiative and aerodynamic components in the 20 cm pan evaporation process accounts for about 1/3 and 2/3 of the total pan evaporation, respectively. Sensitivity tests of four kinds of convention meteorological factors on pan evaporation showed that the pan evaporation were most sensitive to the wind speed, followed by air relative humidity, solar radiation and air temperature, and the corresponding rates of changes were 0.602, -0.590, 0.528 and 0.370, respectively.
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