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2024-11-23 2:13

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Conference: Bucharest University Faculty of Physics 2023 Meeting

Section: Atmosphere and Earth Science; Environment Protection

Title:

Shallow convection memory might explain the transition from shallow to deep convection

Authors:

Cristian-Valer VRACIU (1,2)

^*
Affiliation:

1) Department of Theoretical Physics, Horia Hulubei National Institute of Physics and Nuclear Engineering, Magurele, Romania

2) Doctoral School of Physics, Faculty of Physics, University of Bucharest, Bucharest-Magurele, Romania

E-mail

cristian.vraciu@theory.nipne.ro

Keywords:

Convection, Transition, Cumulonimbus, Dynamical model

Abstract:

The initiation of storm convection in a diurnal cycle is still poorly represented in the weather prediction and general circulation models. This leads to a poor forecast of severe events and large climate uncertainty. The reason for this is represented by our poor understanding of the physical mechanisms controlling the transition from shallow to deep convection. On one hand, the shallow preconditioning is too slow to explain the rapid transition, and on the other hand, the transition is too slow too be explained by a single starting plume developing in the cloud layer. In this work, we discuss the role of shallow cumuli in the initiation of deep convection. By using a simple entraining plume model, we show that the interaction between a convective plume and a passive shallow cumulus helps the former to reach higher altitudes and, in the right conditions, may initiate deep convection. A large-eddy simulation is also performed to simulate a transition from shallow to deep, and we show that indeed the interaction between the passive and active shallow clouds helps the updrafts to better preserve the buoyancy, and thus, to reach higher altitudes. In addition, although the passive cumuli only occupies a very small fraction, the new clouds prefer to develop exactly in the place of the old passive ones. This suggest that the passive clouds, due to their moisturizing effect, change the structure of the transition layer. Therefore, our results suggest that the shallow convective memory is very important in the convective cycle, and it might explain the rapid transition from shallow, non-precipitating, cumulus to deep, precipitating, storm convection. We then propose a predatory-prey dynamical model for shallow and deep convection with shallow memory and cold pools effects.