An Observational Measurement of Entrainment in Midlatitude Deep Moist Convection

open_access
Open Access
Author:
Ejiogu, Amanze
Graduate Program:
Meteorology and Atmospheric Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 12, 2025
Committee Members:
John Peters, Thesis Advisor/Co-Advisor
Colin M. Zarzycki, Committee Member
Jerry Harrington, Professor in Charge/Director of Graduate Studies
Paul Markowski, Committee Member
Keywords:
deep moist convection
entrainment
updraft
thunderstorms
mesoscale meteorology
atmosphere
ERA5
numerical weather prediction
doppler radar
global climate models
Abstract:
Deep moist convection (DMC) has significant short- and long-term impacts on both weather and climate. Entrainment, the phenomenon where updrafts ingest environmental air from their surroundings, can significantly weaken DMC. This makes the task of forecasting thunderstorms difficult, since the nature of entrainment and the mechanisms that drive it are complex. Global climate and numerical weather prediction models utilize cloud parameterization due to the computational difficulty in simulating updrafts and entrainment directly. For both applications, proper quantization of entrainment is necessary to achieve predictive accuracy. Current methods estimate entrainment from theory and computer simulations, which has not been fully confirmed by observation. Furthermore, the observational studies which have been conducted provide conflicting values for the magnitude of entrainment in DMC. In this study, we utilize a thunderstorm tracking dataset, gridded S-band radar data, atmospheric reanalysis, and an entraining bulk plume model to estimate the fractional entrainment rate of tracked thunderstorms. We found that on average, the fractional entrainment rate for DMC in the Central and Eastern Continental United States is the fractional entrainment rate 0.167 per kilometer and that they able to actualize about 16.6% of the convective available potential energy (CAPE) available to them. We also analyzed the level of correspondence between several atmospheric variables and the fractional entrainment rate. Finally, we perform a comparison of the retrieved the fractional entrainment rate with the output from one global climate and two numerical weather prediction models and found that the models tend to poorly estimate the fractional entrainment rate in midlatitude DMC.