從氣象資料估算蒸發量

ESTIMATING EVAPORATION RATE FROM METEOROLOGICAL DATA

10.29417/JCSWC.198711_18(2).0007

徐森雄(Sen-hsiung Hsu)；宋義達(Yih-dah Sung)

蒸發量估算 ； Penman公式 ； Estimating evaporation rate ； Penman formula

中華水土保持學報

18卷2期（1987 / 11 / 01）

83 - 89

繁體中文

本文將Penman所提出估算蒸發量之公式簡化如下：E =〔1.04Q_s（a + b n/N）+0.45（T-T_d）〕x（0.46 + 0.001 T）式中E：蒸發量（mm day^(-1)）Q_s：地表理論日射量（10^(-3) Cal cm^(-2) S^(-1)）a、b：係數n / N：日照率，n爲實測日照時數，N爲理論日照時數T：月平均氣溫（℃）T_d：月平均露點溫度（°C）台灣地區七個測候站資料依據上式所得蒸發量估算值與實測值比較結果，兩者之相關係數頗高，除恒春爲0.78外，其餘台北，台中，台南，高雄，花蓮及台東等地均在0.90以上。年平均誤差率爲1〜9％，月平均誤差率則爲4〜11％。充分說明此一簡化後之蒸發量估算式在本省有相當之適用性。

The Penman formula for the evaporation rate from free water surface is simplified to the following: E (1.04O_s (a +b^n/N)+0.45 (T-T_d)) x (0.46 + 0.01T) where E: Evaporation rate (mm day^(-1)) Q_s: Theoretical global solar radiation on earth surface (10^(-3) cal cm^(-2)S^(-1)) a, b: Coefficient calculated from Q/Q_s=a+b^n/N, where Q is observed global solar radiation on earth surface. n/N: Sunshine rate, where n is observed sunshine duration and N is theoretical sunshine duration. T_d: Monthly mean air temperature (°C). Monthly mean dewpoint (°C). The formula applies to a long periodical evaporation rate estimation would be limited to a range of annual mean wind speeds from 1-5 m s^(-1) and monthly mean air temperature over 5°C Compared the estimated evaporation rate by this formula with the observed evaporation rate had been treated in Taiwan. and their correlation coefficient in Taipei. Taichung, Tainan, Kaoh-siung, Hualien and Taitung were more than 0.90. The errors alter from 1-9% for annual means and 4-11% for monthly means.