Environmental Controls on Convective Mass Flux and Anvil Properties in the Tropics

The strength and severity of convective storms depends on the strength of vertical motions and associated convective mass flux (CMF) of condensate-laden air in updrafts. CMF also impacts the detrainment of air and condensate into storm anvils, which are critical to cloud-radiative forcing and cloud-climate feedbacks. Nevertheless, the relationship between CMF, the environment, high anvil clouds, and storm severity is not well understood and involves covarying non-linear factors. Here, we contribute to the upcoming NASA INvestigation of Convective UpdraftS (INCUS) Earth Venture Mission, which will address these gaps in our knowledge through a global systematic exploration and measurement of CMF in tropical convection. The goals of this study are to (1) determine the environmental controls of CMF in modeled tropical convective storms, (2) identify connections between modeled CMF and anvil cloud properties, and (3) understand the physical mechanisms and feedbacks responsible for the observed covariability between CMF, anvils, and the environment.

One component of INCUS is the production of an extensive high-resolution database of simulated tropical convective systems using the Regional Atmospheric Modeling System (RAMS) and Weather Research and Forecasting (WRF) models at 100 m horizontal grid spacings with 30 second output. The INCUS simulation dataset is an expanding collection of diverse storm morphologies in a variety of maritime and continental tropical environments and includes scattered congestus, multi-cell convective clouds, squall lines, and tropical cyclones.

To answer our science questions regarding CMF and anvils, over 50,000 individual storm updrafts and their connected anvils in the INCUS simulation database are tracked and linked in space and time with the tobac cloud tracking algorithm. Using statistical factor analysis, the temporal evolution of anvil height, area, depth, and radiative effects can be related back to the properties of its parent updraft(s), including vertical velocity, CMF, microphysical quantities and processes, rainfall rates, and associated environmental variables. Pairing the factor analysis with variance inflation techniques, we can also establish where and when multicollinearities amongst predictive factors exist. This analysis will inform our understanding of the environmental controls on tropical CMF and anvils, and consequently on the understanding of storm evolution and intensity.