Estimation of Monthly Average Sunshine Duration over China Based on Cloud Fraction from MODIS Satellite Data

The sunshine duration (SSD) model described herein combines meteorological observation data from an extensive network of weather stations, MODIS satellite cloud cover data, and a high-resolution digital elevation model to produce high-resolution SSD maps of China. The model yielded low difference between the measured and estimated values at 672 standard weather stations. The mean absolute bias error (MABE) of the monthly mean daily SSD for 2001-2003 was 0.15-0.26 h and the relative bias error (RABE) was 2.34-4.64%. To further validate the model, the observation data from the intensive weather stations (with high spatial resolution) in Jiangsu and Qinghai not used in the calculations, were used for comparison with the estimated values. The annual mean MABE values in Jiangsu and Qinghai during 2001-2003 were less than 0.5 h, and the annual mean RABE values below 5%. Thus, one can conclude that the SSD model is reliable and stable. The spatial distribution of the SSD was also examined, which indicated that the macroscopic distribution of SSD in China determined using MODIS satellite data was more objective and more detailed than the distribution by interpolation of weather station observations of SSD.