I would start by looking at what others have done toward creating integrated MW precipitation products, as differences in performance/calibration from different sensors must be dealt with in this context. For instance, see what was done at Remote Sensing Systems (http://www.ssmi.com):

Hilburn, KA, FJ Wentz, 2008, Intercalibrated passive microwave rain products from the unified microwave ocean retrieval algorithm (UMORA), Journal of Applied Meteorology and Climatology, 47, 778-794.

Thank you for Robert. Yes, it is very important to search other's work. And I have done it. But I can't find some paper on the validation of hourly PMW rain rate. Do you have any experience?

Dear Xu,

I have not worked on this problem per say. It seems however that you are stuck with a time-space problem. Gauge data are point observations integrated over a certain interval, while satellite retrievals are instantaneous but represent an estimate over a large area. Some assumptions must be used then to establish a correspondence. You might draw some inspiration from these recent publications, that seem to address a similar problem:

Labo, Eszter, 2012: Validation studies of precipitation estimates from different satellite sensors over hungary - Analysis of new satellite-derived rain rate products for hydrological purposes. JOURNAL OF HYDROLOGY Volume: 468 Pages: 173-187 DOI: 10.1016/j.jhydrol.2012.08.031

Roebeling, R. A.; Wolters, E. L. A.; Meirink, J. F.; et al., 2012: Triple Collocation of Summer Precipitation Retrievals from SEVIRI over Europe with Gridded Rain Gauge and Weather Radar Data. JOURNAL OF HYDROMETEOROLOGY Volume: 13 Issue: 5 Pages: 1552-1566 DOI: 10.1175/JHM-D-11-089.1

Yamamoto, Munehisa K.; Ueno, Ken'ichi; Nakamura, Kenji, 2011: Comparison of Satellite Precipitation Products with Rain Gauge Data for the Khumb Region, Nepal Himalayas. JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN Volume: 89 Issue: 6 Pages: 597-610 DOI: 10.2151/jmsj.2011-601