The Effective Environmental Width of Convective Updrafts in the Tropics

One of the major objectives of the National Aeronautics and Space Administration (NASA) INvestigation of Convective UpdraftS (INCUS) satellite mission is to understand the relationship between the environment of a storm and its convective mass flux (CMF). This entails determining how large the effective environment surrounding the storm is and which environment variables influence the storm CMF and other properties the most. In this study, we address these two questions at the scale of individual updrafts using output from numerical simulations. As part of the INCUS mission, we are conducting numerous high-resolution simulations of deep moist convection using the Regional Atmospheric Modeling System (RAMS) and Weather Research and Forecasting (WRF) models. These simulations encompass a wide range of storm morphologies showing multiple convective modes: scattered shallow convection, isolated deep convection, mesoscale convective systems, and tropical cyclones and occurring in an exhaustive variety of regions in the Tropics. The horizontal and vertical grid spacings used in these simulations are approximately 100 m. The model data output frequency is 30 seconds, and the model initial and lateral boundary conditions are derived from ERA5 reanalysis. The individual updrafts in these simulations are tracked using the tracking and object-based analysis of clouds (tobac) tool. First, we focus on understanding what constitutes the environment of the updraft. This is done by producing mean environmental soundings around the tracked updrafts in annuli of increasing width (which represent an expanding environment) and then analyzing how the correlation between the ambient soundings and updraft properties varies as a function of environmental width for a given storm type and tropical location. We delve into the physical reasoning driving the differences in the effective environmental width for updrafts in different storms. Second, we estimate the skill of various thermodynamical and dynamical environmental properties including CAPE, CIN, low-, mid- and upper-level relative humidity, 0-6 km shear, etc. in predicting updraft properties such as lifetime, area, time-averaged CMF, maximum vertical velocity, surface precipitation rate, updraft-averaged ice water and liquid water path. Information about the effective environmental width and the most influential environmental variables has the potential to improve forecasting of severe weather in addition to serving the objectives of INCUS mission.