Calibration and Validation of the Hargreaves‐Samani Model for Reference Evapotranspiration Estimation in China

Abstract

Abstract Daily meteorological data of 12 years from 838 stations over China were collected and applied to calibrate the HS model by comparison between the values of ET 0 calculated from the original HS and those from the PM model. The calibrated HS model was evaluated by the distribution and values of statistical indices. After calibration, the mean values of the mean absolute error (MAE) and the root mean square error (RMSE) decreased by 24.6 and 23.9%, respectively. The correlation coefficients ( R ) for most areas were greater than 0.9, and the minimum R increased by 2% compared with the values of the original. The minimum and maximum slope of the zero‐intercept regression lines changed from 0.839 to 0.898 and from 1.46 to 1.04 during the validation period, respectively. The distribution of the statistical indices also showed better performance in most areas. The calibrated HS model produced the greatest ET 0 estimation in the subtropical monsoon climate zone and the south‐western part of the temperate monsoon climate zone. Although the performance of the HS model improved after calibration in the plateau and mountain climate and temperate monsoon climate zones, the original HS model had high enough accuracy. However, for the tropical climate regions, the HS model failed to give reliable results even in calibrated form. Overall, the study illustrated that the calibrated HS model has higher accuracy for most climate zones. © 2019 John Wiley & Sons, Ltd.