M channels to radar measurements ground precipitationOn the sensitività of Modis visibile /1.6 .

The statistical approach shows an high correlation between the VIS/1.6μm combination and the radarmeasured ground precipitation. This is a new and interesting result that deserve to be analysed and explained. By an elementary physical procedure the 1.6μm and 3.9μm effective radii were inferred. By analysing some convective and stratiform precipitation cases what emerged is that the statistical PoP function describes the precipitation better than the physical retrieved parameters. However the two cases analysed show an interesting characteristic: the combined use of the two retrieved effective radius can have different behaviour for different kind of clouds. In fact in all the convective cases analysed the 3.9μm effective radius is clearly greater than the 1.6μm effective radius. This does not happen in several stratiform case where the two effective radii are comparable. This results, supported also by previous works (Chang and Li, 2002, Rosenfeld et al., 2004), indicate this area of research as a very promising area about the estimation of precipitation from satellite measurements.