Importance of snow to global precipitation

Precipitation controls the availability of drinking water and viability of the land to support agriculture. Failure to accurately predict the location, magnitude and frequency of precipitation not only impacts numerical weather forecasting but also climate modelling. It has been proposed that most rainfall events originate from ice that has melted to form rain. Here we use remote sensing from space-borne cloud radar to quantify that idea. A new metric is constructed to quantify the fraction of rain eventsat the surface that are linked to snow melting at a higher altitude. CloudSat is used to show the global variation of the importance of snow in the precipitation process. In the tropics, subtropics, midlatitude, polar regions and globally 0.3, 0.4, 0.8,>0.9 and 0.5 respectively, of all precipitation events (>1 mm/d) are linked to the production of snow in clouds.