Sistema baseado em regras fuzzy do tipo Takagi-Sugeno aplicado a ecos de radares meteorológicos
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Data
2016-01-25
Autores
Martinez, Vinícius Machado [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O campo de refletividade de ecos observados por radares meteorológicos está sujeito a interferências de fenômenos físicos da atmosfera que podem resultar em interpretações não realísticas do fenômeno observado. Buscando ajustar o campo de refletividade de ecos detectados simultaneamente por dois radares meteorológicos ao longo da distância, este estudo desenvolveu um sistema baseado em regras fuzzy (SBRF), do tipo Takagi-Sugeno de primeira ordem, que combina as variáveis distância (km) e refletividade (dBZ) para expressar a refletividade ajustada de alvos mais distantes de um radar em relação a outro radar mais próximo, de modo que os efeitos das interferências nas medidas dos radares possam ser minimizados. Os dados utilizados são oriundos de dois radares meteorológicos do IPMet/UNESP, localizados nos municípios de Bauru (22,3583° S; 49,0278° W) e Presidente Prudente (22.175°1 S; 51.3743° W), no Brasil, no período de um ano de dados (2010) do produto CAPPI, faixa de 3.5km de altitude. A saída do sistema é nomeada refletividade fuzzy (RF) e é obtida através de um conjunto de nove curvas de regressão linear, cujos coeficientes angulares e lineares foram estimados pelo método dos mínimos quadrados. Dois parâmetros foram utilizados para análise das curvas obtidas: o coeficiente de correlação de Pearson e o coeficiente de determinação. O sistema foi aplicado a 20.514 dados referentes a 18 pixels distribuídos sobre uma faixa de comum cobertura dos radares. O modelo foi avaliado através das estatísticas de erro médio (BIAS), erro quadrático médio (MSE) e pelo teste de Kolmogorov-Smirnov. Os resultados obtidos demonstram a capacidade do sistema em aproximar o campo de refletividade de dois radares que operam sobre uma área de comum cobertura, devendo constituir-se como uma ferramenta alternativa de interpretação no monitoramento de chuvas, nos processos de modelagem ambiental e em sugestões futuras de estimativa de chuva por radar.
The reflectivity field of echoes observed by weather radars is subjected to the interference of physical phenomena of the atmosphere that can result in unrealistic interpretations on its characteristics. Aiming to adjust the reflectivity field of echoes simultaneously detected by two weather radars over a distance, this study developed a Takagi-Sugeno fuzzy rule-based system, whose input variables are the distance(km) and the reflectivity(dBZ) of the echoes, in order to obtain the adjusted reflectivity of echoes more distant from a radar in relation to another closer radar that is considered to be less susceptible to interference and, therefore, more realistic. The data used are from two weather radars of IPMet/UNESP, located in the municipalities of Bauru (22.3583° S; 49.0278° W) and Presidente Prudente (22.1751° S; 51.3743° W), Brazil, which collected data of the CAPPI product in the period of one year (2010), with a sampling altitude range of 3.5 km. The system output is named “Fuzzy Reflectivity” (FR), obtained through the fuzzy approach of a set of nine linear regression curves, whose angular and linear coefficients were estimated by the method of least squares. Two parameters were used for the analysis of the curves obtained: the Pearson correlation coefficient and the coefficient of determination. The system was applied to 20,514 data related to 18 pixels spread over a range of common coverage of the radars. We evaluated the system performance by means of statistical parameters: average error (bias), mean square error (MSE) and Kolmogorov-Smirnov test. The results obtained demonstrate the system ability to refine the modeling of the issue in question in relation to the traditional statistical approaches, properly adjusting the reflectivity field of the echoes observed by two radars that operate over an area of common coverage and serving as an alternative interpretation tool in the monitoring of rains, in processes of environmental modeling and in future suggestions of rain estimate by radar.
The reflectivity field of echoes observed by weather radars is subjected to the interference of physical phenomena of the atmosphere that can result in unrealistic interpretations on its characteristics. Aiming to adjust the reflectivity field of echoes simultaneously detected by two weather radars over a distance, this study developed a Takagi-Sugeno fuzzy rule-based system, whose input variables are the distance(km) and the reflectivity(dBZ) of the echoes, in order to obtain the adjusted reflectivity of echoes more distant from a radar in relation to another closer radar that is considered to be less susceptible to interference and, therefore, more realistic. The data used are from two weather radars of IPMet/UNESP, located in the municipalities of Bauru (22.3583° S; 49.0278° W) and Presidente Prudente (22.1751° S; 51.3743° W), Brazil, which collected data of the CAPPI product in the period of one year (2010), with a sampling altitude range of 3.5 km. The system output is named “Fuzzy Reflectivity” (FR), obtained through the fuzzy approach of a set of nine linear regression curves, whose angular and linear coefficients were estimated by the method of least squares. Two parameters were used for the analysis of the curves obtained: the Pearson correlation coefficient and the coefficient of determination. The system was applied to 20,514 data related to 18 pixels spread over a range of common coverage of the radars. We evaluated the system performance by means of statistical parameters: average error (bias), mean square error (MSE) and Kolmogorov-Smirnov test. The results obtained demonstrate the system ability to refine the modeling of the issue in question in relation to the traditional statistical approaches, properly adjusting the reflectivity field of the echoes observed by two radars that operate over an area of common coverage and serving as an alternative interpretation tool in the monitoring of rains, in processes of environmental modeling and in future suggestions of rain estimate by radar.
Descrição
Palavras-chave
Lógica Fuzzy, Refletividade, Precipitação, Sistemas baseados em regras fuzzy, Método de Takagi-Sugeno, Fuzzy modeling, Radar meteorológico, Sistemas difusos, Takagi-Sugeno method, Meteorology, Weather radar