Improvement of models for the estimation of downward atmospheric long-wave radiation for retrieving net radiation fluxes based on remote sensing
定量遥感地表净辐射通量所需大气下行长波辐射估算模型改进

With the measurement data of the down ward atmospheric radiation and the air temperature and humidity of the surface layer in 2004 in the Xiaotangshan region of Beijing, the verification was done by making use of the widely-used downward atmospheric radiation model,includingt enmodels for cloud-free days: ngstr(1918), Brunt(1932), Swinbank1( 1963), Idso &; Jackson(1969), Swinbank2(1963), Brutsaert1(1975), Brutsaert2(1982) , Idso(1981), Prata(1996), Iziomon et al.(2003),and two models for cloudy days:Jacobs(1978) and Iziomon(2003). The results show: (1)for cloud-free days, I ziomon(2003)'s model has a good performance and can be used directly for the are a; and (2) for cloudy days, the two models, Jacobs(1978) and Iziomon(2003), have relative large errors. With measured data, this paper puts forward a modified downward atmospheric radiation assessment model based on Iziomon(2003)'s model and the measurement information.A better match between the estimation value and the actual measured value is achieved.The application of the data about the air temperature and humidity from the regular weather stations only represents the contribution of the surface layer which could not reflect the effect given by the whole atmosphere to the downward atmospheric radiation, so there will be errors if the water vapor situation is different from the surface layer and the upper layer. The basic idea of the modi fied model is to calculate the downward atmospheric radiation with an expression of the atmospheric emissivity in Iziomon's model by making use of the observati on value from the thermal infrared thermometer with an angle of 37°.