Revisiting the Hail Radar Reflectivity-Kinetic Energy Flux Relation by Combining T-Matrix and Discrete Dipole Approximation Calculations to Size Distribution Observations

Autor(es)

Cecchini, Micael A. ; Heymsfield, Andrew J. ; Honeyager, Ryan ; Field, Paul ; Machado, Luiz A. T. ; Da Silva Dias, Maria A. F.

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF THE ATMOSPHERIC SCIENCES; v. 79, n. 7, p. 14-pg., 2022-07-01.

Resumo

The retrieval of hail kinetic energy with weather radars or its simulation in numerical models is challenging because of the shape complexity and variable density of hailstones. We combine 3D scans of individual hailstones with measurements of the particle size distributions (PSD) and T-matrix calculations to understand how hail reflectivity Z changes when approximating hailstones as spheroids, as compared to the realistic shapes obtained by 3D scanning technology. Additionally, recent terminal velocity relations are used to compare Z to the hail kinetic energy flux E-.. We parameterize the hail backscattering cross sections at L, S, C, and X bands as a function of size between 0.5 and 5.0 cm, matching the range of the observed PSDs. The scattering calculations use the T-matrix method for size parameters below 1.0 and the discrete dipole approximation (DDA) method otherwise. The DDA calculations are done for 48 digital models of realistic hailstones of sizes between 1 and 5 cm. The DDA cross sections are calculated for multiple orientations and averaged assuming a fully random orientation distribution to provide a single value per hailstone. The T-matrix reflectivity assuming solid ice spheres presents negligible differences to DDA results for size parameters below 1.0. Therefore, T matrix was used to fill in the gaps left by the DDA calculations. The results are mapped to the same size bins of the observed PSDs, allowing the calculation of the radar reflectivity. This is then correlated to E-., allowing a potential improvement of past retrieval methods of E. from Z in multiple wavelengths. (AU)

• Processo FAPESP: 20/13273-9 - Anatomia de nuvens convectivas sobre a Amazônia (ACCA)
• Beneficiário: Micael Amore Cecchini
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 17/17047-0 - O ciclo de vida de aerossóis e nuvens na Amazônia: emissões biogênicas, emissões de queimadas e impactos no ecossistema
• Beneficiário: Paulo Eduardo Artaxo Netto
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 15/14497-0 - Previsão imediata de tempestades intensas e entendimento dos processos físicos no interior das nuvens: o SOS-CHUVA (Sistema de Observação e Previsão de Tempo Severo)
• Beneficiário: Luiz Augusto Toledo Machado
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 18/09082-3 - Características das distribuições de tamanho de diferentes espécies de gelo no espaço de fase Gamma
• Beneficiário: Micael Amore Cecchini
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Processo FAPESP: 17/04654-6 - Estudo dos espaços de fase macro e microfísicos em tempestades: perspectivas para o nowcasting
• Beneficiário: Micael Amore Cecchini
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado