Comparison of the evolution of convective organization indexes in idealized and realistic LES simulations of Amazonian cloud fields

• Grant number: 25/11700-0
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: September 09, 2025
• End date: March 08, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Meteorology
• Principal Investigator: Micael Amore Cecchini
• Grantee: Gabriel Ghiraldello Balestra
• Supervisor: Thibaut Dauhut
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Université De Toulouse, France
• Associated to the scholarship: 24/04763-3 - Analyzing the effects of aerosols and moisture on the organization of shallow cloud fields in the Amazon, BP.MS

Abstract

Climate models have a long-lasting issue about reproducing the evolution of cumulus cloud fields from shallow to deep convection in the tropics. It has been shown that deep clouds are generally triggered too quickly, causing errors in the prediction of the rainfall diurnal cycle. Since clouds are major players in the energy and moisture redistribution over the Amazon, this issue has significant consequences about the prediction of the rainforest's future climate. Because they cover the whole globe, climate models have relatively poor spatiotemporal resolution compared to regional models. Therefore, the progressive organization of convective cloud fields, from shallow convection in the morning to deep convection in the late afternoon, has to be parameterized. Such parameterizations involve diagnostics of the thermodynamic profile of atmospheric columns to infer whether there is enough instability to trigger deep convection. Triggers of deep convection often depend on the value of Convective Available Potential Energy (CAPE) and its time derivative. However, information about the spatial organization of convective cloud fields is not taken into account. This study aims at shortening that gap using different types of high-resolution simulations. During the domestic part of this FAPESP Master scholarship, the student has been analyzing the organization of shallow cumulus cloud fields using idealized simulations with the RAMS (Regional Atmospheric Modeling System) model. This enables a theoretical understanding of the convective indexes available in the literature that aim at synthesizing the complex organization of cloud fields into a single number. However, there is a need to understand how those indexes change over the transition of shallow to deep convection in more realistic scenarios. This BEPE will tackle this issue, benefitting from the international advisor's experience with realistic simulations of Amazonian clouds with the Meso-NH (Mesoscale Non-Hydrostatic model) model. The student will apply his methods of calculating organization indexes to the realistic simulations. This will help answer our hypothesis that the convective organization indexes present specific patterns of evolution during the shallow-to-deep convective transition. If so, this could be an important added information to the triggering functions of deep convection in climate models. (AU)