An Introductory Study of Warm Rain Productivity in Convective Clouds Influenced by Regional Climate Change

Rain development in a convective cloud can be greatly affected by its overall depth, the depth of the cloud below the freezing level (0 °C), and the amount of aerosol particles that the cloud ingests from the surrounding air. Global and regional climate models offer projections of how thermodynamic properties of the atmosphere might change in the future, but the influence of these projected thermodynamic differences upon the depth over which warm rain processes can act in convective clouds has not been fully explored. Moreover, preliminary studies of such influences have not investigated changes at the regional scale, nor have they considered regional differences in atmospheric aerosol that greatly influence the warm rain process.

Thermodynamic soundings from climate model runs performed over the past 30 years, and projected 30 years into the future, are used in conjunction with a 1D warm rain model to provide insight on how warm rain productivity may change in the “warm” part of convective clouds over the U.S. Regional variations of aerosol, assuming a constant fraction of such aerosol act as cloud condensation nuclei, are also considered. These results will be useful for future studies of mixed-phase convective clouds with more complex numerical models, to determine where and how the precipitation in such clouds over the U.S. might be more susceptible to changes in regional climate.

The present study was conducted as part of a new sophomore-level, research-oriented laboratory at Purdue University in the Atmospheric Science program.