Moisture Sources of Precipitation Using Convection-Permitting Simulations: A Study Over South America

Climatological analyses of moisture sources of precipitation have traditionally relied on reanalyses or models that parameterize convection. Convection-permitting models (CPMs) are increasingly used in climate studies, as they better represent many precipitation processes than non-CPMs. We found significant differences in precipitation moisture sources over the Amazon Basin using 1-year CPM and non-CPM WRF simulations with moisture tracers. Notably, the CPM estimates that about half of precipitation in the central Andes comes from the Amazon basin; a 20%–30% higher estimate than the non-CPM. This suggests long-term CPMs with tracers could improve climatological estimates. However, their high computational cost is prohibitive. To overcome this, we developed a revised 2L-DRM model that replicates CPM-with-tracers estimates at a fraction of the cost, using only standard outputs. We applied this model to South America, analyzing precipitation moisture sources across 15 regions. 2L-DRM can be used for other regions as continental-scale CPM climatological simulations become available.