A Quest to Understand and Model Regional Precipitation and its Future Changes
The Earth’s hydrological cycle is expected to undergo significant alterations under increasing global temperatures. While there is considerable understanding of these changes on a global scale, the impact at regional-to-subregional levels remains poorly understood and subject to much greater uncertainty. These local-scale changes are of great scientific and socio-economic interest and are especially relevant for community-scale decision-makers. Here, we investigate the 21st-century seasonal precipitation changes over the United States (US) and further assess the sources of projection uncertainty using models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Under global warming, a robust intensification of mean winter precipitation is evident across the US and its subregions, except for the South Great Plain, where future multi-model mean changes are very small and highly uncertain. Notably, winter projections exhibit relatively high consistency, whereas other seasons, such as summer and autumn, are characterized by a wide range of uncertainty. Similarly, we find a robust projected increase in wet winter precipitation extremes, with approximately 5–10 out of every 30 winters expected to exceed the very wet threshold in most parts of the US. Our overall results suggest that the projected enhancement in future winter precipitation is largely modulated by coupled dynamic and thermodynamic responses (i.e., nonlinear term – associated with transient eddies), while being partly offset by thermodynamic responses associated with increased moisture availability. Although this work highlights the need to better constrain the dynamic response, the overall findings point to a high likelihood of increasing impacts from winter precipitation in the US in response to climate change.