Abstract:

Based on the platform of opensource geographic information system GRASS,500 m resolution datasets of clearsky radiation (including beam,diffuse and reflected radiation) in the Yangtze River Basin were firstly calculated with processmodel r.sun and programming language Shell,which can help to understand spatiotemporal pattern of energy over the basin, and provide data for macroclimatic and ecological modeling.The results are as follows:(1) Validations show that r.sun model on the retrieval of the clearsky radiation of the Yangtze River Basin performs relatively well,with the MPE (37%),MAPE (75%) and RMSE (64%) of related clearsky index.The model can be further used in other regions of China.(2) Annual mean radiation,with an average value 2424±245 MJ/(m2·d),has a significant gradient. Beam,diffuse and reflected components are quite different,with ratios of the annual average global radiation 841%, 156% and 3% respectively.(3) Global radiation and its variability both decrease along the three terrain ladders from west to east. Atmospheric attenuation along with the elevation plays an important role in the pattern of clearsky radiation.(4) Seasonal distributions of clearsky radiation are asymmetry,with the percentage order of the annual average global radiation,summer (316%)>spring (292%)>autumn(219%)>winter(173%).Monthly changes of the clearsky radiation share with the inverted “U”shaped curve.Monthly beam and diffuse radiation have similarly changing trend,but their proportion shifts with the atmospheric turbidity during the year