A Preliminary Analysis of the Contributions of Line End Vortices, Gravity Waves, and Environmental Flow to Mesoscale Convective System Rear Inflow and Stratiform Region Structure in Numerical Simulations

Mesoscale convective systems (MCSs) produce heavy rainfall and damaging winds which can have devastating impacts on communities in their path. Within an MCS, there are many circulations that impact the overall strength and longevity of these systems. Low-frequency gravity waves, line-end vortices, and environmental flow all contribute to the rear-to-front flow in an MCS. Low frequency gravity waves help to initiate the rear-to-front flow of MCSs. These gravity waves are created by the atmosphere’s response to vertical variations in the diabatic heating in the convective and stratiform regions with longer horizontal propagation likely in the stratiform region due to the stable stratification. These circulations within MCSs, particularly in the stratiform region, are represented poorly in model forecasts due to model parameterizations in this region not accurately characterizing the latent heating responsible for initiating these circulations.

This study uses numerical simulations of MCSs that occurred during two United States Department of Energy/Atmospheric System Research sponsored field campaigns, Midlatitude Continental Convective Cloud Experiment (MC3E) and Plains Elevated Convection at Night (PECAN), to isolate the contributions of line-end vortices, gravity waves, and environmental flow to MCSs' rear-to-front flow. The preliminary analysis is conducted on two cases that occurred in the Central Plains on 20 May 2011 during MC3E and in Nebraska on 17 June 2015 during PECAN. These cases are simulated using the Advanced Research version of the Weather Research and Forecasting (WRF) model at convection-allowing and large-eddy–resolving scales. The total rear-inflow will be decomposed to assess the individual contributions from the line-end vortex, gravity waves, and environmental winds. The model-simulated three-dimensional wind are subject to a vorticity/divergence inversion, Fourier decomposition, and low-pass filter, respectively, to quantify the contributions of the MCS line-end vortex, gravity wave, and environmental wind contributions to the rear-to-front flow.