Summary
Thornthwaite's (1948) empirical method of estimating potential evapotranspiration (PE) has been preferred by several scientists in India to Penman's (1948) theoretical combination approach, because of the former's simplicity. However, in view of the doubts expressed in various quarters regarding the applicability of Thornthwaite's method for monsoon climates, a comparison is made of the performance of these two methods over different parts of India, using about 26 years of data at 15 stations spread over the country. Various aspects of the manifestations and their differences are presented. It is found that Thornthwaite's method gives considerably higher estimates ofPE and shows lower inter-annual variability than Penman's method during the southwest monsoon season. A systematic annual variation of the difference between the two methods is also noticed which is found to be mainly due to the actual vapor pressure and sunshine duration included in Penman's method.
Zusammenfassung
Thornthwaites (1948) empirische Methode zur Bestimmung der potentiellen Evapotranspiration (PE) wurde auf Grund ihrer Einfachheit von vielen indischen Wissenschaftlern der theoretisch-empirischen von Penman (1948) vorgezogen. Da die Anwendbarkeit der Methode Thornthwaites für Monsunklimate von manchen Kreisen in Zweifel gezogen wird, wird hier ein Vergleich zwischen beiden Methoden mit Daten von etwa 26 Jahren von 15 Stationen, die über ganz Indien verteilt sind, gezogen. Es zeigt sich, daß Thornthwaites Methode während des Südwestmonsuns höhere Werte mit geringerer Schwankung zwischen den Jahren liefert als die Penmans. Ebenso wurde ein systematischer Unterschied in der jährlichen Variation zwischen beiden Methoden festgestellt, der sich vor allem auf den tatsächlichen Dampfdruck und die Sonnenscheindauer, die in Penmans Methode berücksichtigt werden, zurückführen läßt.
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Kumar, K.K., Kumar, K.R. & Rakhecha, P.R. Comparison of Penman and Thornthwaite methods of estimating potential evapotranspiration for Indian conditions. Theor Appl Climatol 38, 140–146 (1987). https://doi.org/10.1007/BF00868097
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DOI: https://doi.org/10.1007/BF00868097