6a.6 Comparing Trmm and Ground-based Radar Observations in Israel during Intense Precipitation Events in March 2003

Ground-based and TRMM precipitation radars provide a complementary view: the Ground-based Radar (GR) measures rain from a lateral direction, while the TRMM radar sees it from the top. There are enormous differences between these two instruments. Mention can be made of the different operation frequencies, sampling volumes, geometrical viewing angles, attenuation, sensitivity and times of acquisition. Consequently, a quantitative comparison between TRMM Precipitation Radar (TPR) and GR is a challenge, as can be seen for instance in Bolen and Chandrasekar (2003). Shape and size of the sampling volumes of the two radars at the same location are different. However, the fact that different ranges and viewing angles cause such significant differences represents also an opportunity: by averaging many echoes in a given region, it is possible to use the quasi-orthogonal and independent view of one sensor for checking the observations of the other one.