Fog and stratus formation on the coast of Brazil

et al. 2011

Rev. bras. meteorol.

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RESUMONeste trabalho analisou-se a estrutura dos sistemas meteorológicos associados às precipitações intensas em Alagoas entre 2003 e 2006. Foi feita a análise das imagens de satélite no canal infravermelho, de produtos de reanálise do National Centers for Environmental Prediction (NCEP) e dados de precipitação de dezessete postos pluviométricos, espalhados em diferentes regiões do Estado. O objetivo desse estudo foi analisar as causas da formação das precipitações intensas e determinar os sistemas meteorológicos associados. Os casos de precipitação intensa foram registrados no Outono/ Inverno. Além disso, metade dos eventos ocorridos entre a primavera e o verão aconteceu em janeiro. As Perturbações Ondulatórias nos Ventos Alísios, a Corrente de Jato do Nordeste Brasileiro e as extremidades das frentes frias foram os sistemas que estiveram mais relacionados às precipitações intensas. Complexos Convectivos de Mesoescala provocaram boa parte dos temporais no oeste do Estado, o que não foi verificado no leste. Exemplificando o método de análise utilizado, um caso foi discutido. Palavras-chaves: Sistemas Sinóticos, Precipitações Intensas, Alagoas. ABSTRACT: SYNOPTIC SYSTEMS ASSOCIATED TO HEAVY PRECIPITATION IN THE STATE OF ALAGOASStructures of meteorological systems, associated with heavy precipitation in the Alagoas State, for the 2003-2006 period were studied. Infrared satellite images, reanalysis data products of the National Centers for Environmental Prediction (NCEP) and data from seventeen Alagoas pluviometric stations were used. The goal of this study is the analysis of the heavy precipitation causes and determination of the associated weather systems. Heavy precipitations were usually registered during autumn/ winter seasons. Also, half of all spring/summer heavy precipitations events occurred in January. Wave Disturbances in the Trade Winds, Brazilian Northeast Jet Streams and Cold Front Extremities were associated with heavy precipitations. Almost all heavy precipitations events were connected with Mesoscale Convective Complexes in the west region of the State and usually did not occur in the east region. To exemplify the used analysis method a case study is discussed.

Section: Frequência Das Precipitações E Sistemas Meteorológicos Assocunclassified

Sistemas sinóticos associados às precipitações intensas no estado de Alagoas

Silva

Федорова

et al. 2011

Rev. bras. meteorol.

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“…Very few investigations of St cloud formation and associated precipitation have been elaborated for the northern Brazilian coast. Some information was published during the last 10 years (Fedorova, 1999;Silveira, 2003, Fedorova et al, 2007, Fedorova et al, 2008. Frequencies of fog and stratus cloudiness formation were higher in the south than on the northern coast (Silveira, 2003, Fedorova et al, 2008.…”

Section: Introductionmentioning

confidence: 99%

“…Some information was published during the last 10 years (Fedorova, 1999;Silveira, 2003, Fedorova et al, 2007, Fedorova et al, 2008. Frequencies of fog and stratus cloudiness formation were higher in the south than on the northern coast (Silveira, 2003, Fedorova et al, 2008. Mean data of the fog events for the southern and northern coasts were 93 fog days and 2 fog days per year, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Also, fog/stratus formation was associated, in general, with wave disturbance in the trade winds (WDTW) field on the north coast. Classification of the temperature and dew-point vertical profiles for different fog/stratus physical processes was developed (Fedorova et al, 2008). Stable layers in the vertical profiles were not observed on the north coast and the humid layer was very narrow in all cases.…”

Section: Introductionmentioning

confidence: 99%

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Rare events of stratus clouds on the northeast coast of Brazil

Gomes

Fedorova

2011

Rev. bras. meteorol.

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One event of three consecutive days and another of four consecutive days of Stratus clouds were registered at the Maceio airport on the northeast coast of Brazil. This is a very rare phenomenon for equatorial regions and it was analyzed using the high resolution (10km) ETA model, NCEP reanalysis, satellite data and conventional data supplied by the Hydrometeorological Directory DHM-SERHI/AL and by the Department of Flight Protection of the Zumbi dos Palmares airport. Wave disturbance in the trade winds and weak ascendant movements at low levels (1000 and 925hPa) were identified. At the same time, anticyclonic curvature at high levels formed descendant movements and subsidence inversion. These vertical movements combined with a stable layer between 850 and 700hPa created a very humid layer at the low levels. The precipitation forecasted by the ETA model with 24h antecedence presented a satisfactory result for an average quantity of precipitation. Nevertheless, the spatial distributions of forecasted and observed precipitation were different. Precipitation during all days was not forecasted for the coastal region, and for the west region the forecasted precipitation was more intense than the observed ones.

“…On the other hand, when this moisture convergence at low levels interacted with downward movement associated with the jet stream, fog was detected. Therefore, both intensive precipitation events and fog formation have been associated with baric troughs in the field of trade winds (from now on wavy disturbance in the trade winds -WDTWs) (Molion and Bernardo, 2002;Rodrigues, 2007;Fedorova et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Adverse meteorological phenomena associated with low‐level baric troughs in the Alagoas State, Brazil, in 2003

Rodrigues

Fedorova

Atmospheric Science Letters

2010

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Baric troughs were studied over the Alagoas State, Brazil, in 2003. The relationship between these synoptic systems, weekly sea surface temperature anomaly and adverse meteorological phenomena in the Alagoas State, was analyzed. The maximum trough frequency occurred at low levels during the wetter and colder season in the investigated region (June and July). Most of the troughs were observed at 1200 UTC. It was also noted that 87% of the troughs was associated with wavy disturbance in the trade winds on the northwestern periphery of the subtropical South Atlantic High. These troughs were associated with meteorological phenomena in a stable and an unstable atmosphere.