Space-time scaling in high-intensity Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE) storms

Abstract Direct diagnostic evaluation of the moisture tendency in the moisture equation is very difficult in practice because two poorly measured terms, moisture convergence and precipitation, dominate the equation. Using the near constancy in space and time of the tropical temperature profile, a variety of energy and entropy based equations have been employed to obtain indirect estimates of the moisture budget. In this paper rigorous versions of the energy and entropy equations are developed. The strengths and weakness of these two formulations are complementary, allowing the authors to estimate moistening and drying tendencies with high confidence when the two formulations are used together. This study applies the theory to data from Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). The results demonstrate how convection regulates the tropospheric humidity, drying the atmosphere when it becomes too moist, and moistening it when it becomes too dry.

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Sensibilidade de conjuntos de nuvens a variações de parâmetros microfísicos: parte I - simulação de controle

Revista Brasileira de Meteorologia ◽

10.1590/s0102-77862013000100002 ◽

2013 ◽

Vol 28 (1) ◽

pp. 13-24 ◽

Cited By ~ 1

Author(s):

André de Sena Pinheiro ◽

Alexandre Araújo Costa

Keyword(s):

Atmospheric Modeling ◽

Ensemble Model ◽

Regional Atmospheric Modeling System ◽

Tropical Ocean ◽

Toga Coare ◽

Ocean Atmosphere ◽

Regional Atmospheric Modeling

Este trabalho é o primeiro de uma série de quatro artigos, com o objetivo de analisar como variações em parâmetros microfísicos afetam o ciclo de vida de nuvens de fase mista, para diferentes condições de estabilidade vertical, adotando como ferramenta uma versão de "cloud ensemble model" - CEM do Regional Atmospheric Modeling System (RAMS). São utilizados dados do Período de Obervação Intensiva (Intensive Observing Period - IOP) do Tropical Ocean Global / Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) como forçante para o CEM. Este foi calculado para três regimes, a depender da atividade convectiva: "médio", em que foi considerada a média das variáveis para todo o IOP, "ativo" (convecção mais intensa) e "suprimido" (convecção menos pronunciada). Para cada regime, calculou-se a média das componentes zonal e meridional da velocidade do vento e as forçantes advectivas (horizontal mais vertical) de temperatura potencial e umidade específica. Tais forçantes foram assimiladas pelo CEM em diferentes testes de sensibilidade, descritos nas partes seguintes desta série de artigos. Na parte I, são apresentados os resultados referentes à simulação controle, mostrando como um CEM estabelece uma condição de quase-equilíbrio resultante da resposta da convecção às forçantes de grande escala estacionárias.

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Transition between Suppressed and Active Phases of Intraseasonal Oscillations in the Indo-Pacific Warm Pool

Journal of Climate ◽

10.1175/jcli3924.1 ◽

2006 ◽

Vol 19 (21) ◽

pp. 5519-5530 ◽

Cited By ~ 25

Author(s):

P. A. Agudelo ◽

J. A. Curry ◽

C. D. Hoyos ◽

P. J. Webster

Keyword(s):

Large Scale ◽

Transition Period ◽

Numerical Models ◽

Convective Available Potential Energy ◽

Lower Troposphere ◽

Diagnostic Study ◽

Tropical Ocean ◽

Toga Coare ◽

Ocean Atmosphere ◽

Intraseasonal Oscillations

Abstract Intraseasonal oscillations (ISOs) are important large-amplitude and large-scale elements of the tropical Indo-Pacific climate with time scales in the 20–60-day period range, during which time they modulate higher-frequency tropical weather. Despite their importance, the ISO is poorly simulated and predicted by numerical models. A joint diagnostic and modeling study of the ISO is conducted, concentrating on the period between the suppressed and active (referred to as the “transition”) period that is hypothesized to be the defining stage for the development of the intraseasonal mode and the component that is most poorly simulated. The diagnostic study uses data from the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). It is found that during the transition period, the ocean and the atmosphere undergo gradual but large-scale and high-amplitude changes, especially the moistening of the lower troposphere caused jointly by the anomalously warm sea surface temperature arising from minimal cloud and low winds during the suppressed phase and the large-scale subsidence that inhibits the formation of locally deep convection. Using a cloud classification scheme based on microwave and infrared satellite data, it is observed that midtop (cloud with a top in the middle troposphere) nonprecipitating clouds are a direct response of the low-level moisture buildup. To investigate the sensitivity of ISO simulations to the transitional phase, the European Centre for Medium-Range Weather Forecasts (ECMWF) coupled ocean–atmosphere climate model is used. The ECMWF was run serially in predictive ensemble mode (five members) for 30-day periods starting from 1 December 1992 to 30 January 1993, encompassing the ISO occurring in late December. Predictability of the active convective period of the ISO is poor when initialized before the transitional phases of the ISO. However, when initialized with the correct lower-tropospheric moisture field, predictability increases substantially, although the model convective parameterization appears to trigger convection too quickly without allowing an adequate buildup of convective available potential energy during the transition period.

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