Contributions of the liquid and ice phases to global surface precipitation: Observations and global climate modeling

The pathways investigated are 1) precipitating ice (ice/snow/graupel) that forms above the freezing level and melts to produce rain (S) followed by additional condensation and collection as the melted precipitating ice falls to the surface (R); 2) growth completely through condensation and collection (coalescence), warm rain (W); and 3) precipitating ice (primarily snow) that falls to the surface (SS).

To quantify the amounts, data from satellite-based radar measurements-CloudSat, GPM, and TRMM-are used, as well as climate model simulations from the Community Atmosphere Model (CAM) and the Met Office Unified Model (UM). Total precipitation amounts and the fraction of the total precipitation amount for each of the pathways is examined latitudinally, regionally, and globally. Carefully examining the contributions from the satellite-based products leads to the conclusion that about 57% of Earth's precipitation follows pathway S, 15% R, 23% W, and 5% SS, each with an uncertainty of +/- 5%.