Abstract
Incoming solar radiation is one of the main climatic variables, and frequently considered as an input to hydrological model and crop growth model. The present study aimed to develop a preliminary model for estimating daily incoming solar radiation in Gia Lam district, Hanoi, Vietnam. Five empirical models were calibrated based on the relationship between daily incoming solar radiation and each of daily sunshine duration and daily temperature range. All the climatic variables were measured at Hanoi University of Agriculture located in Gia Lam district, Hanoi, Vietnam. The performance of the models was compared with regards to estimation accuracy and characteristics of the models. The best performance for the present data set was found at modified Angström model, and followed by original Angström model, Hargreaves model with linear regression, Hargreaves model with power regression, and original Hargreaves model. The present result suggested the use of Hargreaves model with linear regression in the case where only daily temperature range was available for modelling incoming solar radiation. For the better estimation of incoming solar radiation, it is necessary to calibrate these empirical models based on the climatic observation data at longer period of time.
