Numerical Assessment of Advective and Diffusive Dynamics of Interacting and Isolated Prototypical Convectively Initiated Circulations

TL;DR

This study evaluates a simplified model (KRoNUT) for representing convective circulations, comparing it to high-resolution simulations, and explores how advection and diffusion influence the dynamics of isolated and interacting convective systems.

Contribution

The paper introduces and validates the KRoNUT model for bulk convective flow representation and analyzes the roles of advection and diffusion in circulation dynamics.

Findings

KRoNUT accurately reproduces flow tendencies from high-resolution simulations.

Horizontal advection significantly influences circulation evolution without buoyancy.

Interactions can stabilize or cluster circulation centers.

Abstract

The bulk circulation associated with convective clouds includes not only a region of updraft and cloudy air but also a region of compensating descent and cloud-free air and horizontal motions coupling these regions. The Kinematic Representation of Non-rotating Updraft Tori (KRoNUT) model is a simple representation of this entire flow. First, the skill of the KRoNUT in representing flows from a high resolution full-physics simulation of marine tropical convection is compared to various plume representations of convection. Then the KRoNUT is used to construct bulk descriptions of the dry dynamics of isolated and interacting convective circulations under the influence of advection and diffusion (only). Cross sections of advective and diffusive tendencies show that while vertical advection of the vertical wind is the most important advective tendency in clouds, the horizontal component of the convective circulation and advection thereof plays a crucial role in the evolution of circulations in the absence of buoyancy. Strong curvature of the flow near the surface and near the updraft core results in locally strong diffusive tendencies that depend on scale. Cross sections of tendencies from the KRoNUT compare favourably to results from the simulation. Interacting circulations are shown to exhibit a wide range of dynamics with some cases of interactions leading to unique stability of geometric properties of otherwise evolving flows and some leading to geometric clustering of circulation centers.