Satellite observation system of rain events is quickly expanding with the new microwave sensors. And several global rainfall products are broadcasted on the Web. This paper focuses on two products: the GSMAP- MVK+ and the GPCP-1DD. It performs a bias regional analysis and relates the estimation errors to the algorithm design. The main results is, whereas the most advanced microwave estimator performs better for local scale rainfall retrieval, the orographic phenomena are deeply underestimated. This conclusion raises the issue of adapting the downscaling method in front of significant orographic effects.