Analysis of the high-resolution merged precipitation products over China based on the temporal and spatial structure score indices

Based on the three indices of spatial and temporal skill score and structure function, the investigation into the applicability of the daily merged precipitation, and the two datasets of precipitation respectively retrieved from the satellites of CMORPH and TRMM in China are performed. The spatial-temporal distributions of errors of these precipitation data are also analyzed with the focus on the quality of the merged precipitation data. The results indicate that, for the whole area of China, the spatial and temporal precision of the merged precipitation is observably promoted compared with that of both the CMORPH and TRMM precipitation. For the merged and satellite data, their performances on simulating the spatial and temporal distribution in summer are all superior to in winter. The simulation qualities in the southeastern region of China are generally better than in the northwestern region. The Yangtze-Huaihe River Valley and South China are the two regions showing the best quality of the merged precipitation. However, the Tibet Plateau and northwest China have the poorest effect of the improvement. Another significant feature after precipitation merging is that both spatial skill scores (SS) and temporal skill scores (ST) are improved obviously. Compared to summer, the values of SS and ST are raised more remarkably in winter. By comparing the structure function values of the three sets of evaluation data and observation data in the different regions, we can clearly see that, in the Yangtze-Huaihe River Valley, South China, North China and northeast China, with the increase of the distance between any two points within the regions, the structure function curves of the observed and merged precipitation are always very close. In northwest China and the Tibet Plateau, the structure function of the merged precipitation has large deviation between the merged and observed precipitation. In southwest China, due to the complex terrain, the satellite data are unable to give the accurate simulation of actual precipitation. So the observed data plays a more important role in this region. In the Yangtze-Huaihe River Valley, South China, and North China, the growth rates of structure function curves of the merged precipitation are larger than that in the northeast China. It reflects that the heterogeneities of precipitation distribution in the three regions of the Yangtze-Huaihe River Valley, South China, and North China, in which the precipitation is more influenced by the mesoscale weather system than that in northeast China.