ABSTRACT.A climatology of cold fronts at the coast of State do Santa Catarina, Brazil, is established based on 10-year period (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999) of NCEP-NCAR reanalysis data. The cold front passages were objectively identified taking into account the wind shifts to a southerly direction, as well as the persistence of southerly wind for at least one day, and a decreasing of air temperature. The results show that, on the average, 3 to 4 cold fronts reach coast of Santa Catarina, each month, with an interval of 8 days. The composite data analysis, using the date of days of cold front passages at Santa Catarina as reference, shows clearly a climatological pattern of evolution, with cold front moving typically from southwest to northeast. In terms of seasonal mean, during winter, one day before reaching coast of Santa Catarina (day -1) the cold front is observed at Rio Grande do Sul. After passing at Santa Catarina (day 0), it continues to move equatorward, reaching the coast of Rio de Janeiro one day later (day +1), until it reaches latitudes close to 20˚S (day +2), in the its stage of dissipation. In the third day, after the passage at Santa Catarina, the cold front is no more observed. Similar pattern of evolution is observed during summer, though the cold fronts are less intense and of slightly more rapid dissipation.Keywords: climatology of cold fronts, movement of cold fronts, cold fronts at the coast of Santa Catarina, Brazil. RESUMO. Uma climatologia de frentes friasé estabelecida para o litoral do Estado de Santa Catarina, com base nos dados de reanálises do NCEP-NCAR, do períodode 10 anos, de 1990 a 1999. As passagens de frentes frias foram objetivamente identificadas levando em conta o giro do vento para direção sul, persistência do vento de sul por pelo menos um dia, e uma queda de temperatura do ar simultânea ao giro do vento ou até dois dias depois. Os resultados mostram que, na média, de 3 a 4 frentes frias atingem a costa de Santa Catarina, mensalmente, com um intervalo de 8 dias. As análises da composição de dados, usando como referência os dias de passagens de frentes frias em Santa Catarina, mostram claramente um padrão climatológico de evolução com frente fria movendo-se tipicamente de sudoeste para nordeste. Em termos das médias sazonais, durante o inverno, um dia antes da passagem em Santa Catarina (dia -1), a frente friaé observada no Rio Grande do Sul, e depois de passar por Santa Catarina (dia 0), continua avançando para latitudes mais baixas, alcançando o litoral do Rio de Janeiro um dia depois (dia +1), até atingir posteriormente latitude de aproximadamente 20˚S (dia +2), já em fase de dissipação. No terceiro dia após a passagem por Santa Catarina, ela nãoé mais identificada.Padrão climatológico de evolução semelhanteé observado no verão, embora nessaépoca as frentes frias tenham menor intensidade e dissipação ligeiramente mais rápida.Palavras-chave: climatologia das frentes frias, movimento das frentes frias, frentes frias no litoral de Santa Catar...
ABSTRACT:Intense wind events at the southern Brazilian coast cause severe socio-economic losses. Generally, such events have been associated with extratropical cyclones over the Southwest Atlantic Ocean. The purpose of this study is to identify favoured locations and the processes through which the winds are associated with the extratropical cyclones. Using a statistical analysis, the wind speed observed at nine meteorological stations was compared with cyclone depth and offshore distance. Both cyclone depth and location were obtained through an objective procedure of identifying and tracking. Generally, the winds are well associated with the extratropical cyclones only south of 28°S. Altitude also plays an important role in this relationship. Furthermore, the cyclones influence the observed wind field up to 1200 km inland at higher latitude locations. For stations near 28°S, cyclones further from the coast have an influence, but with smaller statistical significance.
The state of Santa Catarina presents significant spatial variations in its climate, with different regional peculiarities. Wind is considered an important meteorological variable, but it is not sufficiently studied and there is a shortage of information on this subject in the region of Santa Catarina. Thus, the objective of this article was to analyze the behavior of the winds in five regions of the state, with different aspects: altitude, topography and climatology patterns. For that, daily data from National Institute of Meteorology of direction and speed of the winds were used from 1974 to 2016. The conventional meteorological stations used were: Chapecó, Campos Novos, Lages, Indaial and Florianópolis. The data were submitted through consistence analysis, monthly descriptive statistics of the velocity were obtained, the predominant direction was characterized through frequency analysis and a conceptual model of prevailing winds in the state was created. Regarding wind speed, Florianópolis and Campos Novos registered the highest speeds during the whole year. In the analysis of wind direction, the prevalence of South Atlantic subtropical anticyclone was observed in most of the year in Florianópolis (circulation from north), Lages and Campos Novos (from northeast). In Chapecó, the predominant east wind direction is associated with the low pressure system in the Paraguay region. For Indaial, the orography has a strong influence on the local circulation, favoring a southwest wind direction, by the formation of the mountain-valley breeze, which has as a forcing the air temperature differences between the valley and the mountain in the night period.RESUMO: Apesar do estado de Santa Catarina possuir pouca variação na latitude, apresenta variações espaciais significativas no seu clima, como verificado neste estudo. O vento é considerado uma importante variável meteorológica, porém não é suficientemente estudado e existe uma escassez de informações sobre esse assunto na região de Santa Catarina. Sendo assim, o objetivo deste artigo foi analisar o comportamento dos ventos em regiões do estado, com diferentes aspectos: altitude, topografia e padrões climáticos. Para tanto, foram utilizados dados diários no Instituto Nacional de Meteorologia (INMET) da direção e velocidade dos ventos no período de 1974 a 2016. As estações meteorológicas convencionais utilizadas foram: Chapecó, Campos Novos, Lages, Indaial e Florianópolis. Após consistidos, os dados diários de vento foram _________________Revista Brasileira de Climatologia_________________
Temporal rainfall distribution is an important information for the preparation of the design hyetograph, directly influencing peak flow. This study analyzes the temporal rainfall distribution of Florianópolis city. We used rainfall data from 1986 to 2012 obtained from the Brazilian National Meteorological Institute (INMET). Heavy rainfall events were classified and individualized, and intensities were determined at each 5% interval of the duration. Rainfall was classified in Huff quartiles and identified by season and duration. Rainfall accumulation curves in the 10-90 percentiles were determined as well as 50% probability curves for each season and duration. The results showed that type I rainfall is the most frequent and that summer rains have a more anticipated pattern. Important differences were found between rainfall durations. The advance coefficient varies with rainfall duration, and averaged 0.389.
In this study three cases of extreme rainfall events are analyzed in Florianopolis, Santa Catarina (SC), on Brazil’s coast, lying between the mountains and the South Atlantic Ocean in southeastern South America. The largest rainfall totals, 200–300 mm in 12–24 h, resulted in flash floods. ECMWF 6-hourly 1.5° × 1.5° data were used to determine the synoptic fields and quasigeostrophic forcing, along with observational data from local networks, for subsynoptic analyses. In case C1, during May 2010, there was a frontal passage. In C2 and C3 (January 2008 and February 1979, respectively) the coastline separated a ridge over the continent from a trough over the sea at the surface, with an atmosphere of low baroclinicity predominating at 500 hPa. All three events were characterized by postfrontal conditions; the presence of an anticyclone over the sea, centered at 35°–40°S; and slow-moving or quasi-stationary midlevel cyclones over the continent, at 27 °S. The circulation generated in the cyclone resulted in strong (10 m s−1) and persistent low-level east-northeast winds along the coast of SC, favoring the influx of heat and humidity on days with heavy rain. The upward motion at 850 hPa was concentrated over the affected areas and stronger than that at 500 hPa. Even so, the moist air that reached the mountain in a conditionally unstable environment rose only to middle levels. The features presented were similar to those observed for orographic rain events in Europe and the United States.
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