Iniciação de tempestades convectivas em um ambiente tropical úmido
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Data
2008-06-09
Autores
Lima, Maria Andrea [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Para determinar como se inicia a convecção na região sudoeste da Amazônia, foram analisados dados do TRMM/LBA (Tropical Rainfall Measuring Mission / Large-scale Biosphere Atmosphere). A base para determinar onde e quando a convecção iniciou foi o radar banda-S, com polarização dual (S-Pol), do National Center for Atmospheric Research (NCAR). Utilizaram-se, adicionalmente, dados do canal visível do satélite GOES-8 para identificar piscinas frias produzidas pela precipitação convectiva. Essas informações, em conjunto com dados topográficos de alta resolução, foram utilizadas na determinação dos mecanismos possíveis de disparos da convecção. A elevação do terreno na área de estudo varia de 100 a 600m. Este estudo apresenta os resultados de 5 de fevereiro de 1999. Um total de 315 tempestades iniciou-se dentro do raio de 130km do radar S-Pol. Nesse dia, classificado como de fraco regime de monção, a convecção desenvolveu-se em resposta ao ciclo diurno do aquecimento solar. Cúmulos rasos espalhados durante a manhã desenvolveram-se em convecção profunda no início da tarde. As tempestades tiveram início após as 11h, com um pico de iniciação entre 15 e 16h. As causas de início de tempestades foram classificadas em 4 categorias. O modo mais comum de iniciação foi o levantamento forçado por frente de rajada (36%). A categoria, que inclui forçantes topográficas (>300m), sem a influência de nenhum outro mecanismo, é responsável por 21% das iniciações e a colisão de frentes de rajada por 16%. Nos 27% restantes, não foi possível a identificação de nenhum mecanismo. O exame de todos os dias do experimento TRMM/LBA mostrou que o dia estudado em detalhe foi representativo de muitos outros dias. Um modelo conceitual para o início e a evolução de tempestades é apresentado. Esses resultados, que devem ter implicações para outros...
Radar and satellite data from the Tropical Rainfall Measuring Mission / Large-scale Biosphere Atmosphere (TRMM/LBA) project have been examined to determine causes for convective storm initiation in the southwest Amazon region. The locations and times of storm initiation were based on the National Center for Atmospheric Research (NCAR) S-band dual-polarization Doppler radar (S-Pol). Both the radar and GOES-8 visible data were used to identify cold pools produced by convective precipitation. This data along with high-resolution topographic data were used to determine possible convective storm triggering mechanisms. The terrain elevation varied from 100 – 600 m. Tropical forests cover the area with numerous clear cut areas used for cattle grazing and farming. This study presents the results from 5 February 1999. A total of 315 storms initiated within 130 km of the S-Pol radar. This day was classified as a weak monsoon regime where convection developed in response to the diurnal cycle of solar heating. Scattered shallow cumulus during the morning developed into deep convection by early afternoon. Storm initiation began about 1100 LST and peaked around 1500-1600 LST. The causes of storm initiation were classified into 4 categories. The most common initiation mechanism was caused by forced lifting by a gust front (36%). Forcing by terrain (>300 m) without any other triggering mechanism accounted for 21% of the initiations and colliding gust fronts 16%. For the remaining 27% a triggering mechanism was not identified. Examination of all days during TRMM/LBA showed that this one detailed study day was representative of many days. A conceptual model of storm initiation and evolution is presented. The results of this study should have implications for other locations when synoptic scale forcing mechanisms are at a minimum... (Complete abstract click electronic access below)
Radar and satellite data from the Tropical Rainfall Measuring Mission / Large-scale Biosphere Atmosphere (TRMM/LBA) project have been examined to determine causes for convective storm initiation in the southwest Amazon region. The locations and times of storm initiation were based on the National Center for Atmospheric Research (NCAR) S-band dual-polarization Doppler radar (S-Pol). Both the radar and GOES-8 visible data were used to identify cold pools produced by convective precipitation. This data along with high-resolution topographic data were used to determine possible convective storm triggering mechanisms. The terrain elevation varied from 100 – 600 m. Tropical forests cover the area with numerous clear cut areas used for cattle grazing and farming. This study presents the results from 5 February 1999. A total of 315 storms initiated within 130 km of the S-Pol radar. This day was classified as a weak monsoon regime where convection developed in response to the diurnal cycle of solar heating. Scattered shallow cumulus during the morning developed into deep convection by early afternoon. Storm initiation began about 1100 LST and peaked around 1500-1600 LST. The causes of storm initiation were classified into 4 categories. The most common initiation mechanism was caused by forced lifting by a gust front (36%). Forcing by terrain (>300 m) without any other triggering mechanism accounted for 21% of the initiations and colliding gust fronts 16%. For the remaining 27% a triggering mechanism was not identified. Examination of all days during TRMM/LBA showed that this one detailed study day was representative of many days. A conceptual model of storm initiation and evolution is presented. The results of this study should have implications for other locations when synoptic scale forcing mechanisms are at a minimum... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Previsão de tempo, Tempestades, Convecção (Meteorologia), Radar Doppler, Convective initiation, Cold pools, Gust front, Nowcasting
Como citar
LIMA, Maria Andrea. Iniciação de tempestades convectivas em um ambiente tropical úmido. 2008. xiii, 92 f. Tese (doutrado) - Universidade Estadual Paulista, Faculdade de Ciências Agronômicas de Botucatu, 2008.