Evaluation of application of several net radiation calculation methods in Huanghuaihai Plain

Penman and Penman-Monteith formulas are among the most widely used approaches to calculating reference crop evapotranspiration using the meteorological data. The net radiation used in those formulas is estimated with the temperature, sunshine hours, humidity, and some location-parameters. However, validation and evaluation of the calculation of the net radiation are seldom conducted when those formulas are applied. This paper dealt with the evaluation using the measured net radiation data measured by Yucheng Comprehensive Experimental Station located in Huanghuaihai Plain. The approaches of БерляндМ.Е., Penman, Brunt, and Deng Genyun were used to calculate the long wave radiation term of the net radiation in Penman formula. It was found that the estimated net radiation agreed best with the measured ones when the БерляндМ.Е. approach was adopted. Meanwhile, the calculated solar radiation was very close to that calculated by FAO Penman-Monteith. The relative errors of the calculated and measured solar radiations were higher in November, December and January than those in other periods. The authors also proposed an empirical formula for estimating the net solar radiation simply on the basis of the global solar radiation in this region.