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Instituto Nacional de Pesquisas Espaciais – INPE (2013)

Propriedade radiativas e microfísicas das nuvens continentais : uma contribuição para a estimativa da precipitação de nuvens quentes por satélite

Calheiros Alan James Peixoto

Titre : Propriedade radiativas e microfísicas das nuvens continentais : uma contribuição para a estimativa da precipitação de nuvens quentes por satélite

Auteur : Calheiros Alan James Peixoto

Université de soutenance : Instituto Nacional de Pesquisas Espaciais – INPE

Grade : Doutorado em Meteorologia 2013

Résumé
Between 2010 and 2012, the CHUVA project collected information regarding cloud and rain in different precipitation regimes in Brazil. Up to March 2012, CHUVA had concluded four field campaigns, located in the North, Northeast and Southeast regions of Brazil, covering the semi-arid, Amazonas, intertropical regions. The purpose of this study is to present, from the statistical point of view, the cloud and rain liquid water profiles and integrated parameters for different cloud types and regimes. The synergy of several instruments allows us to describe cloud process characteristics and to classify rain events. Microwave radiometer, LiDAR, radar, and disdrometer were employed in this study. A rain type classification was developed using vertical profiles of reflectivity (VPR) and polarimetric variables from dual-polarization radar (XPOL). The integrated cloud liquid water (ILWC) and Water Vapor were retrieved with a microwave groundbased radiometer using a neural network, radiosondes, and a GPS receiver, this later only for IWV. For rainy conditions, the profiles from the liquid water content (LWCR) and their integrated (ILWR), bellow the melting layer, properties were estimated by Micro Rain Radar (MRR) and XPOL VPRs. For nonprecipitating clouds, the IWV and ILWC values were larger for the sites in Northeast Brazil near the coast than for the other regions. For rainy cases, distinct LWCR profiles and ILWR were observed for different rain classifications and regions with a distinctive rainfall regime. The ILWR for the convective systems show the highest values, followed by stratiform and warm systems. The clouds in the Vale do Paraiba and Belem showed the largest reflectivity in the mixed and glaciated layers, respectively. In contrast, the coastal sites show larger values of cloud and rain liquid water content for non-precipitating and warm clouds. The Vale and Belem clouds present the deepest clouds and larger convective cloud liquid water. Several analyses are presented, describing the cloud process and the differences among the regions. Based in the warm rain cloud properties obtained in this study, several radiative simulations were performed to check the capability to estimate warm clouds rainfall using microwave radiometers. Several sensitivity tests were performed to evaluate the impact of all parameters contributing to the microwave upward radiation. The warm rain signal is very small when compared with all the others contributions from emissivity variability, moisture and temperature profiles and the different liquid water content. However, the integrated difference between the channels seems to show clear information about rainfall from warm clouds. A discussion about this features and the possible methodology to be employed is presented in the last section.

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Page publiée le 3 avril 2019