水面蒸发量的一种气候学计算方法

用北京日射站和官厅蒸发站的辐射和蒸发资料对彭曼公式进行订正,得出修正公式 E_0=(ΔH_0+γE_α)/(Δ+γ) H_0=1/590.95Q_A(0.167+0.583n/N)-σT_a~4(0.32-0.26e_a~(1/2))(0.30+0.70n/N)] E_a=0.13(e_a-e_d)(1+0.77u),其中H_0是表示为蒸发量单位的辐射平衡,E_a是由风速和饱和差决定的“干燥力”。 自由水面的蒸发量E可用下式表示 E=E_0-F/L,其中F是水面向下的热通量,在升温季节为正值,在降温季节为负值。由于缺少水温梯度观测资料,F不能直接计算。本文建议,对升温或降温季节分别建立水面蒸发E倚蒸发势E_0的回归方程。得出北京地区各月蒸发量的计算公式如下 0.963 E_0-7.0 4—7月 E=0.902 E_0+26.0 9—10月 E_0 8月

A CLIMATIC CALCULATIVE METHOD OF EVAPORATION FROM OPEN WATER

Based on the data of radiation and evaporation from Beijing Solar Radiation Station and Quanting Evaporation Station, the Penman's formula is corrected as where Ho is the radiation balance expressed in evaporation units, Ea is the "drying power" determined from windspeed and the vapour-pressure deficit. Evaporation from open water may be expressed by equation E=E₀-F/L where F is heat flux downward from water surface. During the increasing temperature season its sign is plus, and in decreasing temperature season minus. Since we lack the data of water temperature gradiant, F cannot be directly calculated. In this paper it is suggested that the regressive equations of E depending on Eo may be respectively established during increasing or decreasing temperature season. Thus, the monthly values of evaporation in warm season in Beijing may be estimated by following formulas