Impact of Global Warming on U.S. Summertime Mesoscale Convective Systems: A Simple Lagrangian Parcel Model Perspective

Mesoscale convective systems (MCSs) are the dominant rainfall producer in the U.S. during the warm season, causing natural disasters and severe weather every year. Global climate models have large uncertainty in projecting precipitation changes in the future climate. Here we developed a simple Lagrangian parcel model (see figure below, it includes single- and multi-column models) to investigate the impact of global warming on MCS initiation and growth. The single-column parcel model projects a mean precipitation decrease over the central U.S. and an increase to its east, in agreement with the CMIP5 model projection. It also highlights the crucial role of current climate mean state model bias in influencing future mean precipitation projection. As for convective population, the model captures the decreased occurrence frequency of weak to moderate convection and increased frequency of strong convection due to the increased CAPE and CIN, in agreement with convection-permitting regional simulations. The multi-column parcel model captures readily the cold pool-induced upscale growth feature. It simulates smaller mesoscale clusters over the central U.S. under global warming due to gust front slowdown and subsidence strength enhancement. The model should be a useful tool for investigating the impact of global warming on MCS at mid-latitudes and providing useful guidelines to improve GCM simulations.

Figure Caption

Schematic diagram for the simple Lagrangian parcel model, including (a) the single-column model and (b) the multicolumn model. Panel (c) illustrates the three cold pool interaction mechanisms that are introduced in the multicolumn model to capture the upscale growth feature of MCSs.

Reference

Qiu Yang*, L. Ruby Leung, Zhe Feng, Fengfei Song, Xingchao Chen, 2021: A Simple Lagrangian Parcel Model for the Initiation of Summer-time MCSs over the Central US, Journal of the Atmospheric Sciences, 78(11), 3537-3558, https://doi.org/10.1175/JAS-D-21-0136.1

Qiu Yang*, L. Ruby Leung, Zhe Feng, Xingchao Chen, 2023: Impact of Global Warming on U.S. Summertime Mesoscale Convective Systems: A Simple Lagrangian Parcel Model Perspective. Journal of Climate, https://doi.org/10.1175/JCLI-D-22-0291.1