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Master's Dissertation
DOI
https://doi.org/10.11606/D.18.2009.tde-27042010-133924
Document
Author
Full name
Micheli Fernandes Gonçalves
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2009
Supervisor
Committee
Mendiondo, Eduardo Mario (President)
Antonio, Mauricio de Agostinho
Martins, Eduardo Sávio Passos Rodrigues
Title in Portuguese
Previsão de chuva com auxílio de radar de tempo visando a um sistema de alerta antecipado de cheias em áreas urbanas
Keywords in Portuguese
Inundações
Previsão de chuva
Radar de tempo
Topo dos ecos
VIL
Abstract in Portuguese
Para reduzir as perdas humanas e materiais durante as inundações, é possível realizar estudo conciso da previsão de chuva, etapa principal de um sistema de alerta antecipado de inundação. O uso de informações de radar de tempo, quando acopladas a modelos de previsão de precipitação baseados fisicamente, pode contribuir para o monitoramento e previsão de episódios de chuva intensa. Desta forma, a previsão de chuva, baseada no uso de informações de radar, juntamente com um modelo conceitual de previsão hidrometeorológica, foi descrita neste trabalho. Teve-se por objetivo aperfeiçoar as previsões de chuva de curtíssimo prazo (poucos minutos), que acopladas a um modelo chuva-vazão, podem ser usadas em sistemas de alerta antecipado. O modelo hidrometeorológico adotado, que considera uma nuvem hipotética unidimensional vertical, foi inicialmente desenvolvido por Georgakakos e Bras (1984a) e ampliado, neste trabalho. Para tal, adotou-se o uso das informações de Topo dos Ecos para determinação da altura das nuvens e considerou-se que a componente do modelo relativa à massa de água líquida no interior da nuvem corresponde à estimativa do conteúdo de água líquida integrado verticalmente (VIL) efetuada por radar. Para eventos de natureza frontal quente e convectiva, o modelo geralmente antecipou o início do processo de chuva, embora tenha conseguido simular seu comportamento e o instante em que o pico da precipitação ocorreu. Para os eventos frontais frios, o pico simulado registrou atraso. Para episódios de simulação com VIL maior que 3 Kg/'M POT.2', a chuva simulada acompanhou o comportamento temporal do VIL, mas com influências das variáveis meteorológicas pressão, temperatura e umidade relativa. As lâminas simuladas tornaram-se entrada para o modelo chuva-vazão do SCS, parcialmente calibrado com algoritmo genético. Para a escala de uma pequena bacia hidrográfica urbana brasileira, com estação fluviométrica experimental, preliminarmente, alguns resultados indicam vazões um pouco inferiores e com atrasos na previsão da vazão máxima. A antecedência proporcionada pelo modelo é de 15 minutos e, apesar da simplicidade, conseguiu-se prever o início do processo de precipitação que gerou inundação do córrego urbano.
Title in English
Precipitation forecast aided by weather radar for early warning system of urban floods
Keywords in English
Echo top
Floods
Rainfall forecast
VIL
Weather radar
Abstract in English
To reduce human and material losses during floods it is feasible to concisely study the rainfall forecast as the main part of an early warning system. The use of weather radar information, when linked to physically-based forecast models, can contribute for monitoring and forecasting of intense rainfall episodes. Thus, the rainfall forecast, based on using of radar information along with a conceptual model of hydrometeorological forecast, was outlined in this dissertation. One goal of the study was to improve very short term rainfall forecasts, named as a 'nowcasting' process throughout few minutes, coupled with a rainfall-runoff generation model to be used in early warning system. The hydrometeorological model, a hypothetical vertical 1-D cloud, was initially developed by Georgakakos and Bras (1984a) and further developed in this study to profit signals from radar tracking control volumes of moisture storage. Either 'Echo Top' radar information was addressed to determinate the cloud height, and the vertically-integrated liquid ('VIL') water mass content inside the cloud, estimated by other radar signal, was considered into the model. On the one hand, during rainfall events of hot and convective front genesis monitored with on-field pluviometers, the model results generally anticipated the beginning of the rain process; however the model was capable of not only simulating well the behavior but also the time-step when rainfall monitored peak occurred. On the other hand, and for cold-front events, the simulating peaks depicted a time delay. For simulation episodes with VIL greater than 3 Kg/'M POT.2', the simulated rainfall accompanied the time behavior of VIL, but with influences from weather variables of pressure, temperature and relative humidity. These rainfall depths became inputs of a simple SCS rainfall-runoff model, partially calibrated with genetic algorithms. At the scale of a small brazilian urban river basin with experimental gauging station, some preliminary results modeled streamflows a bit lower than, and with some delay of maximum flow forecasts, observed discharges. The advanced lad time period used by model was of about 15 min and, besides its simplicity, it was quite able to anticipate the beggining of the rainfall process that generated the flood formation at the urban creek.
 
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Publishing Date
2010-05-12
 
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