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A parabolic function to modify Thornthwaite estimates of potential evapotranspiration for the eastern United States

G. J. McCabe
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Abstract

The Thornthwaite potential evapotranspiration model is well known and widely used , but has received some criticism as it is primarily based on air temperature to estimate potential evapotranspiration . Errors of the Thornthwaite model can be analyzed using adjusted pan evaporation as an index of potential evapotranspiration . An examination of ratios of adjusted pan evaporation to Thornthwaite potential evapotranspiration indicates that the ratios are highest in the winter and lowest during summer months. This trend suggests a parabolic pattern. In this study a parabolic function is used to adjust Thornthwaite estimates of potential evapotranspiration . Forty locations east of the Rocky Mountains are analyzed and indicate that a parabolic adjustment of Thornthwaite potential evapotranspiration estimates generally increases correlation with adjusted pan evaporation and decreases error by 20 to 70 percent.

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G. J. McCabe. 2013-05-15. A parabolic function to modify Thornthwaite estimates of potential evapotranspiration for the eastern United States. https://doi.org/10.1080/02723646.1989.10642376

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