The evolution of raindrop spectra: comparisons between modeled and observed spectra along a mountain slope in Switzerland

A comparison is made between the evolution of raindrop spectra as measured at stations in the Swiss Alps separated by vertical distances of the order of 600 m, with that modeled in an axisymmetrical model including detailed microphysics. Results show that under steady rain, weak advective conditions, and rain rates greater than 2 mm h^-1, the model satisfactorily reproduces the features of the observed drop spectrum. Results deteriorate for low rain rates (of the order of 1 mm h^-1) since drop collisions are too few to modify the spectrum significantly. The general agreement between modeled and observed spectra suggests that further considerations of this kind are justified. -Authors