Evaluation of Radar-Rainfall Products over Coastal Louisiana

Radar-rainfall products provide valuable information for hydro-ecological modeling and ecosystem applications, especially over coastal regions that lack adequate in-situ rainfall observations. This study evaluates two radar-based rainfall products, the Multi-Sensor Stage IV and the Multi-Radar Multi-Sensor (MRMS), over the Louisiana coastal region in the United States. Surface reference rainfall observations from two independent rain gage networks were used in the analysis. The evaluation included distribution-based comparisons between radar and gage observations at different time scales (hourly to monthly), bias decomposition to quantify the contribution of different error sources, and conditional evaluation of systematic and random components of the estimation errors. Both products report large levels of random errors at the hourly scale; however, the performance of the radar-rainfall products improves significantly with the increase in time scales. After decomposing the total bias, the results show that the largest contributor to the overall bias in radar-rainfall products is false rainfall detection, followed by missed rainfall. The results also reveal that the Stage IV product experienced a significant improvement over the area in the past few years (post 2015) compared to earlier periods. The results have implications for ongoing and future coastal ecosystem modeling and planning studies.

DETERMINAÇÃO DA EQUAÇÃO INTENSIDADE-DURAÇÃO-FREQUÊNCIA PARA ALGUMAS LOCALIDADES DO ESTADO DA BAHIA

DETERMINAÇÃO DA EQUAÇÃO INTENSIDADE-DURAÇÃO-FREQUÊNCIA PARA ALGUMAS LOCALIDADES DO ESTADO DA BAHIA LORENA JÚLIO GONÇALVES1; CRISTIANO TAGLIAFERRE2; MANOEL NELSON DE CASTRO FILHO3; RODRIGO LACERDA BRITO NETO4; BISMARC LOPES DA SILVA5 E FELIZARDO ADENILSON ROCHA6 1 Departamento de Engenharia Agrícola e Solos da Universidade Estadual do Sudoeste da Bahia (UESB); Estrada do Bem Querer, Km 04; Caixa Postal 95; CEP 45031-900, Vitória da Conquista – BA, [email protected]; 2 Departamento de Engenharia Agrícola e Solos da Universidade Estadual do Sudoeste da Bahia (UESB); Estrada do Bem Querer, Km 04; Caixa Postal 95; CEP 45031-900, Vitória da Conquista – BA, [email protected]; 3 Departamento de Agronomia da Universidade Federal de Viçosa (UFV); Avenida Peter Henry Rolfs, s/n, Campus Universitário; CEP 36570-900; Viçosa – MG; [email protected]; 4 Mestre em Ciências Florestais pela Universidade Estadual do Sudoeste da Bahia (UESB); Rua Madureira, n° 160, Bairro Primavera; CEP 45700-000, Itapetinga – B; [email protected]; 5 Departamento de Engenharia Agrícola e Solos da Universidade Estadual do Sudoeste da Bahia (UESB); Estrada do Bem Querer, Km 04; Caixa Postal 95; CEP 45031-900, Vitória da Conquista – BA, [email protected]; 6 Instituto Federal da Bahia/ Campus Avançado de Vitória da Conquista; Avenida Sérgio Vieira de Mello, n° 3150, Bairro Zabelê; CEP 45075-265, Vitória da Conquista – BA, [email protected]. 1 ABSTRACT The objective of this study was to fit intensity-duration-frequency equations (IDF) for sites in Bahia state, Brazil. Maximum annual rainfall lasting 5, 10, 15, 20, 30, 60, 360 and 1440 minutes were fitted to Gumbel distribution. Equation parameters were estimated using Gauss Newton method for non-linear regressions. According to Kolmogorov-Smirnov test, all equations were fitted to Gumbel distribution. From fitted distributions, maximum annual rainfall intensity was calculated for 2, 10, 20, 50 and 100years return periods, which were used to define the equation for intense rainfall events. Fitting parameters of the equations varied across rain gage stations, especially for the parameter K, suggesting the need for determining these equations for each site, thereby providing information when designing agricultural and hydraulic projects. Keywords: Hydrology. Extreme Rainfall. Distribution of Gumbel. GONÇALVES, L. J.; TAGLIAFERRE, C.; CASTRO FILHO, M. N; BRITO NETO, R. L.; SILVA, B. L; ROCHA, F. A. DETERMINATION OF INTENSITY-DURATION-FREQUENCY EQUATIONS FOR SITES IN BAHIA STATE 2 RESUMO O objetivo deste estudo foi determinar equações de intensidade-duração-frequência (IDF), com base em chuvas extremas para algumas localidades do Estado da Bahia. As precipitações máximas anuais com duração de 5, 10, 15, 20, 30, 60, 360 e 1440 minutos foram ajustadas à distribuição de Gumbel. Os parâmetros da equação foram estimados pelo método de regressão não linear de Gauss Newton. De acordo com o teste Kolmogorov-Smirnov houve ajuste de todas as equações à distribuição de Gumbel. Através das distribuições ajustadas, calcularam-se os valores de intensidade máxima anual de precipitação para períodos de retorno de 2, 10, 20, 50 e 100 anos, que serviram de base para definir a equação de chuvas intensas. Os valores dos parâmetros ajustados das equações variaram entre as estações, notadamente o parâmetro K, evidenciando a necessidade da determinação dessas equações para cada localidade para dimensionamento de projetos agrícolas e de obras hidráulicas. Palavras-chave: Hidrologia. Chuvas Intensas. Distribuição de Gumbel.

CARACTERÍSTICAS DAS CHUVAS E INTERCEPTAÇÃO VEGETAL NO BIOMA CAATINGA

CARACTERÍSTICAS DAS CHUVAS E INTERCEPTAÇÃO VEGETAL NO BIOMA CAATINGA JOSÉ BANDEIRA BRASIL1; HELBA ARAÚJO DE QUEIROZ PALÁCIO2; JOSÉ RIBEIRO DE ARAÚJO NETO2; JACQUES CARVALHO RIBEIRO FILHO3 E EUNICE MAIA DE ANDRADE1 1 Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Campus do PICI, Bloco 804, Fortaleza-CE, Brasil. E-mail: [email protected]; [email protected] Instituto Federal de Educação, Ciência e Tecnologia do Ceará-IFCE, Campus Iguatu, rodovia Iguatu-Várzea Alegre, Km 05, s/n, Iguatu-CE, Brasil. E-mail: [email protected]; [email protected] Departamento de Ciências Ambientais e Tecnológicas, Universidade Federal Rural do Semi-Árido-UFERSA, Mossoró-RN, Brasil; [email protected]. 1 RESUMO A dinâmica da interceptação vegetal depende principalmente das características das chuvas e estrutura do dossel das árvores. Objetivou-se com este estudo analisar o efeito das características das chuvas (classes de precipitação (CP) - CP < 15 mm, 15 ≤ CP < 30 mm, 30 ≤ CP < 60 mm e CP ≥ 60 mm e classes de intensidade (CI) - 1,1 mm h-1 ≤ CI < 5 mm h-1, 5,1 mm h-1 ≤ CI < 25 mm h-1, 25,1 mm h-1 ≤ CI < 50 mm h-1 e CI ≥ 50,1 mm h-1) e as variações sazonais na interceptação em área de caatinga em regeneração. O experimento foi conduzido em uma microbacia experimental no município de Iguatu-Ceará, em seis anos consecutivos, de 2010 a 2015, totalizando 212 eventos. Foram monitorados a precipitação interna, escoamento pelos caules das árvores e perda por interceptação em uma área de 10 x 10 m. A precipitação total foi medida com o auxílio de um pluviômetro do tipo “Ville de Paris” instalado em área aberta. Constatou-se que não houve diferenças sazonais (período chuvoso - janeiro a junho e período seco - julho a dezembro) entre os percentuais médios de Precipitação interna (Pint), Escoamento pelo caule (Esc) e Perda por interceptação (I), em função das características das chuvas e da vegetação. Os resultados demonstram que as menores perdas relativas por interceptação foram observadas nas classes de precipitação > 60 mm e nos eventos mais intensos os percentuais médios de perda por interceptação são menores. Palavras-chave: Classes de chuva, intensidades pluviométricas, variabilidade sazonal. BRASIL, J. B.; PALÁCIO, H. A. de Q.; ARAÚJO NETO, J. R. de; RIBEIRO FILHO, J. C.; ANDRADE, E. M. deRAINFALL CHARACTERISTICS AND VEGETATION INTERCEPTION IN THE CAATINGA BIOME 2 ABSTRACT The mechanism of vegetation interception depends largely on the rainfall characteristics and canopy of the trees. The main objective of this study was to analyze the effects of the rainfall characteristics (precipitation classes (RC) - RC < 15 mm, 15 mm ≤ RC < 30 mm, 30 mm ≤ RC < 60 mm and RC ≥ 60 mm and intensity classes (IC) - 1,1 mm h-1 ≤ IC < 5 mm h-1, 5,1 mm h-1 ≤ IC < 25 mm h-1, 25,1 mm h-1 ≤ IC < 50 mm h-1 and IC ≥ 50,1 mm h-1) and the seasonal variations of the interception in an area with regenerating caatinga. The experiment was conducted on an experimental catchment in the municipality of Iguatu, Ceará, during six consecutive years, from 2010 to 2015, with a total of 212 events. Internal precipitation, tree trunk runoff and loss by interception in areas of 10 x 10 m were monitored. The total rainfall was measured with a “Ville de Paris” rain gage, installed in an open area. No seasonal changes were observed (wet season – January through June – and dry season – July through December) among the average percentages of internal precipitation (Pint), tree trunk runoff (Esc) and loss by interception (I), due to the rainfall and vegetation characteristics. The results show that the smallest relative losses by interception were observed in the precipitation classes over 60 mm and, among the most intense events, the average loss percentages by interception are smaller. Keywords: Rainfall classes, rainfall intensities, seasonal variability.

Evaluation of TRMM rainfall estimates over a large Indian river basin (Mahanadi)

The paper examines the quality of satellite-based precipitation estimates for the Lower Mahanadi River Basin (Eastern India). The considered data sets known as 3B42 and 3B42-RT (version 7/7A) are routinely produced by the tropical rainfall measuring mission (TRMM) from passive microwave and infrared recordings. While the 3B42-RT data are disseminated in real time, the gage-adjusted 3B42 data set is published with a delay of some months. The quality of the two products was assessed in a two-step procedure. First, the correspondence between the remotely sensed precipitation rates and rain gage data was evaluated at the sub-basin scale. Second, the quality of the rainfall estimates was assessed by analyzing their performance in the context of rainfall-runoff simulation. At sub-basin level (4000 to 16 000 km2) the satellite-based areal precipitation estimates were found to be moderately correlated with the gage-based counterparts (R2 of 0.64–0.74 for 3B42 and 0.59–0.72 for 3B42-RT). Significant discrepancies between TRMM data and ground observations were identified at high intensity levels. The rainfall depth derived from rain gage data is often not reflected by the TRMM estimates (hit rate < 0.6 for ground-based intensities > 80 mm day−1). At the same time, the remotely sensed rainfall rates frequently exceed the gage-based equivalents (false alarm ratios of 0.2–0.6). In addition, the real time product 3B42-RT was found to suffer from a spatially consistent negative bias. Since the regionalization of rain gage data is potentially associated with a number of errors, the above results are subject to uncertainty. Hence, a validation against independent information, such as stream flow, was essential. In this case study, the outcome of rainfall–runoff simulation experiments was consistent with the above-mentioned findings. The best fit between observed and simulated stream flow was obtained if rain gage data were used as model input (Nash–Sutcliffe Index of 0.76–0.88 at gages not affected by reservoir operation). This compares to the values of 0.71–0.78 for the gage-adjusted TRMM 3B42 data and 0.65–0.77 for the 3B42-RT real-time data. Whether the 3B42-RT data are useful in the context of operational runoff prediction in spite of the identified problems remains a question for further research.