Abstract
This study employs a pseudo global warming approach to investigate precipitation changes from a mesoscale convective system (MCS) on 14 May 2018 over the eastern United States. An Appalachian-Mountain-crossing MCS is simulated for historical, mid-twenty-first century (2045–2054), and late twenty-first century (2090–2099) climate scenarios. For experiments using ensemble-mean perturbations in atmospheric, soil, and oceanic variables derived from 34 general circulation models, MCS precipitation diminishes by 25% in mid-century and 65% in late century. Experiments testing the sensitivity to these variables separately reveal that atmospheric variables primarily drive precipitation changes. Additional sensitivity experiments quantify MCS responses to temperature, moisture, and wind perturbations separately, with the magnitude of perturbations stratified as low, moderate, or high. Experiments highlight the dominant, though contrasting roles, of the thermodynamic variables. In mid-century, temperature increases lead to reductions in rainfall rate by up to 74.3%, while increased moisture raises rainfall rates by 75.1%. In late century, the MCS fails to initiate for temperature perturbations of all magnitudes. Rainfall rate and precipitation area substantially increase with larger moisture perturbations; while the frequency of heavy (95th percentile) and extreme (99th percentile) precipitation increases more than 100%, with minimal changes in precipitation rate. Finally, ensemble-mean perturbations are added to all variables, except for temperature or moisture, to which either a low or high perturbation is added. MCSs are robust when low temperature or high moisture perturbations are included, though they fail to initiate for low moisture and high temperature perturbations, highlighting the challenges in projecting future MCS behavior.
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