AMS 2024#
Our group at NIU recently presented results at AMS 2024 on changes in mesoscale convective system (MCS) behavior and spatial distribution in a set of continental-scale convection permitting regional climate model output.
A link to the talk can be here (starts at 00:30:00).
What distinguishes our results from past studies utilizing convection-permitting models to study changes in MCS is that we consider how changes in the large-scale circulation may influence the overall MCS response. Due to computational restraints, many studies looking at future changes in extreme precipitation in high resolution numerical models are primarily constrained to quantifying how changes in thermodynamics affect the overall response. We find a shift in the frequency of upper-tropospheric troughs that is overall supportive of an enhanced MCS signature in the eastern United States. However this signal is small relative to the changes in large-scale circulation due to interannual variability. Instead, we classify MCS based on the magnitude of their large-scale forcing at initiation time and find that an increase in MCS in weakly-forced synoptic environments can help to explain a non-negligible increase in the overall MCS frequency.
Overall, these results suggest a shift in the springtime regime that more closely matches what occurs in the warm-season. Namely, MCS that are more easily triggered by sub-synoptic scale features including shortwaves and mid-tropospheric perturbations. Past work has found that sub-synoptic scale features can still lead to MCS formation and development in unfavorable environments and that small synoptic features such as mid-tropospheric perturbations are both observed and projected to increase.