ABSTRACT: A high-resolution simulation of a real case is carried out in Eastern Amazon (Northeastern coast of State of Pará) with the Weather Research and Forecasting (WRF) model in order to analyze/detect local circulation features in the region. To this end, we simulated a case with low interference of synoptic weather systems and precipitation aiming to eliminate the effects of convective systems in local circulations. The performance of the model for the day studied was evaluated and the existence of circulations found in the simulation was confirmed through observational data. The model performance evaluation showed that the model was able to capture most of the patterns for the studied area. The simulation captured the presence of three main circulations: the Sea Breeze (SB), on the coast; the Land Breeze (LB), also on the coast; and the Bay Breeze (BB), which forms on both banks of Marajó Bay. In addition to these three major circulations, the high-resolution simulations also revealed the presence of a river breeze (RB) from Guamá River and a fan-shaped circulation on the entrance of Guajará Bay. The observational data confirmed the presence of Guamá River breeze from the Southeast, which is more active from July to September.

ABSTRACT: Precipitation events are infrequent in the dry quarter (SON) of the Alcântara Launch Center (Centro de Lançamento de Alcântara, CLA), the main launch site of the Brazilian Space Program. However, their occurrence could be a risk for activities during launch missions. In this work, the observational features of wet days (daily precipitation total ≥ 1 mm/day) in the dry quarter of the CLA region were studied. Daily precipitation totals over the course of 37 years (1979-2016, except 2006), outgoing longwave radiation (OLR) data and ERA-Interim reanalysis data were used. On average, in the dry quarter, there were 9 wet days, which accumulated 32 mm. The number and quarterly precipitation total of wet days showed pronounced interannual variability. This variability was negatively and significantly correlated with the interhemispheric sea surface temperature anomalies gradient in the Atlantic Ocean and the wind speed at 925 hPa over the CLA region. Based on a theoretical distribution (log-normal), the probability of occurrence of heavy precipitation days (daily total ≥ 10 mm/day) was only 0.5%. For days with heavy precipitation and deep convection (OLR ≤ 230 W·m-2), over a large area along the northeastern coast of South America including the CLA region, negative OLR differences (from the mean) and the strengthening of favorable conditions for deep convection were found. The large-scale organization of the convective activity and atmospheric features for higher precipitation events obtained in this work could be helpful for nowcasting and short-range weather forecasting during launch missions at the CLA.

ABSTRACT The breeze potential along the Brazilian northern and northeastern coast was studied using wind data from the Climate Forecast System Reanalysis for the period between 1980 and 2010. March and September were considered, which are representative of the rainy and dry (or less rainy) periods, respectively. The Brazilian northern and northeastern coast is composed by meridionally oriented coastlines (Amapá State coast and eastern coast of Northeast Brazil) and a zonally oriented coastline (Brazilian northern coast east of Marajó Island). Along the meridionally oriented coastlines, the breeze potential was mainly related to the zonal wind and extended inland over 1 - 2° from the shore. The daily zonal wind cycle maximum (minimum), which represents the land (sea) breeze potential, occurred at ~0700 UTC (~1900 UTC). Along the zonally oriented coastline, the breeze potential was mainly related to the meridional wind and extended inland and offshore over 2 - 3° from the shore. At the shore, the daily meridional wind cycle maximum (minimum), which represents the land (sea) breeze potential, occurred at ~1000 UTC (~2200 UTC). Phase propagation occurred from the shore inland in March and September and also offshore in September. In general, for the entire Brazilian northern and northeastern coast, the breeze potential frequency was higher in September (20 - 25 days per month). In March, while the frequency slightly decreased over the meridionally oriented coastlines (to 15 - 20 days per month), the frequency sharply decreased over the zonally oriented coastlines to 5 - 10 days per month in landside coastal areas and vanished in seaside coastal areas. Higher frequency was generally related to lower interannual variability, and there was significant correlation between the interannual variability of the frequency and oceanic indices, along specific coastal areas. The features of the breeze potential areas obtained in this study complement the results from others and provide a more complete depiction of breeze features along the entire Brazilian northern and northeastern coast.

Resumo Totais diários de precipitação foram utilizados para identificar os eventos de Precipitação Extrema (PE) na região do Centro de Lançamento de Alcântara (CLA) para o período de set-1984 a ago-2014 (30 anos). Adotando o 99° percentil dos totais diários (44 mm d-1) como limiar de PE, foram identificados 104 eventos no período. O ciclo anual da frequência de eventos e das excedências foi muito semelhante ao ciclo anual da precipitação, com máximo (mínimo) no trimestre MAM (SON). Utilizando as séries de duração parcial, os máximos anuais de total diário (definindo ano hidrológico como os 12 meses a partir de setembro) puderam ser modelados estatisticamente como uma distribuição de Gumbel. A precipitação de 1 dia com tempo de retorno de 100 anos seria de 115 mm, valor inferior aos encontrados na literatura para localidades pertencentes à região do CLA. Para o bimestre de março e abril, que concentrou a maior frequência de eventos, a variabilidade interanual da frequência esteve correlacionada positiva e significativamente (R = +0,44) com o total de precipitação, e a correlação parcial com outros fatores (índice Niño 3, gradiente inter-hemisférico de temperatura da superfície do mar do Atlântico e vento em 925 hPa sobre a região do CLA) não foi significativa. Os dias de PE no bimestre diferenciaram-se dos demais com totais elevados por apresentarem maior número de horas do dia com chuva (14 ± 4 h) e maiores totais horários (p. ex., total horário máximo = 23 ± 9 mm h-1). No bimestre de março e abril de 1996, quando houve a maior frequência de eventos (5 eventos), os dias de PE caracterizaram-se pela ocorrência de atividade convectiva intensa sobre duas grandes áreas: uma zonalmente alongada cobrindo a costa norte do Brasil, e outra cobrindo os Estados de Santa Catarina e Paraná.

Abstract Daily precipitation data were used to identify the Extreme Precipitation (EP) events in the Alcântara Launch Center (Centro de Lançamento de Alcântara, CLA) region for the period from Sept-1984 to Aug-2014 (30 years). Selecting the 99th percentile (44 mm d-1) as the threshold for EP, 104 events were identified in the period. The annual cycle of the EP events frequency and exceedances was similar to the annual cycle of precipitation, with maxima (minima) in the MAM (SON) quarter. Using the peaks-over-threshold approach, the annual maximum daily precipitation (defining hydrological year as 12 months from September) could be statistically modeled as a Gumbel distribution. The 1-day precipitation with return period of 100 years would be 115 mm, which is lower than the values found in the literature for localities within the CLA region. For the March and April bimester, when the largest frequency of events occurred, the interannual variability of the frequency was correlated positively and significantly (R = +0.44) with the total precipitation, and the partial correlation with other factors (such as Niño 3 index, interhemispheric sea surface temperature gradient in the Atlantic and wind at 925 hPa over the CLA region) was not significant. In the bimester, the EP days differed from the others with high totals as they showed greater number of hours with rain (14 ± 4 h) and greater hourly totals (e. g., maximum hourly precipitation = 23 ± 9 mm h-1). In the bimester of a specific year, 1996, when the highest frequency of events (5 events) was found, the EP days were characterized by an intense convective activity over two large areas: one zonally oriented covering the northern coast of Brazil, and the other covering the States of Santa Catarina and Paraná.

ABSTRACT: The interannual variability of precipitation in El Niño/Southern Oscillation-neutral years was studied for the Centro de Lançamento de Alcântara region. Monthly precipitation, sea surface temperature, wind at 925 hPa and outgoing longwave radiation data from various gridded datasets for the 1951-2010 period (60 years) were used. The data grouping was based on terciles. For the Centro de Lançamento de Alcântara in El Niño/Southern Oscillation-neutral years, March is the month of the rainy quarter (March to May) when the interhemispheric gradient of the sea surface temperature anomalies over the Atlantic (GRAD) and the atmospheric circulation at 925 hPa over the Centro de Lançamento de Alcântara were able to best explain the variability of precipitation. In this month, the wind direction at 925 hPa was the factor that explained the highest fraction of precipitation variance (40%), followed by GRAD (30%) and the wind magnitude (20%). For the Centro de Lançamento de Alcântara, in general, above-average precipitation was related to weak north-northeasterly low-level winds and southward GRAD, while below-average precipitation was related to strong east-northeasterly low-level winds and northward GRAD. These features were related to an eastward expansion of the Amazon convection towards the northern Northeast Brazil and might be related to a slight southward displacement of the Intertropical Convergence Zone in above-average precipitation years.

ABSTRACT: The rainy season features for the Alcântara Launch Center region (2°S-3°S; 44°W-45°W), located at the northern coast of Brazil, were obtained by using the Climate Prediction Center/National Oceanic and Atmospheric Administration daily precipitation data from 1979 to 2012 accumulated to pentads. The rainy season onset (demise) was defined as the first pentad when precipitation is greater (lower) than the climatological annual average, and this behavior lasts for three out of the four following pentads. The average rainy season features were: 28 January as onset day; 16 June as demise day; 140 days as length; 1527 mm as total precipitation (about 80% of the annual value); and 10.9 mm day -1 as intensity (rain rate). The uncertainty on these climatological values due to the use of different precipitation datasets was estimated as few days for the onset/demise days and length, 100 mm for the total precipitation and about 1 mm day-1 for the intensity. Except for intensity, the rainy season features showed large interannual variability: standard variation of about one month for onset/demise days, and coefficient of variation of 33 and 40% for length and total precipitation, respectively. The three-week period between 24 March and 13 April belonged to the rainy season of all years. In general, longer (shorter) duration was related to early (late) onset, late (early) demise, and higher (lower) total precipitation. Within the rainy season, on an average, precipitation was lower than 0.1 mm day-1 in only four to five days; therefore, the occurrence of “no-rain” days was rather uncommon.

Este trabalho apresenta um estudo observacional das características da Zona de Convergência Intertropical (ZCIT) na porção central do Oceano Atlântico. A variabilidade da posição, largura e intensidade (precipitação média) da ZCIT Atlântica durante 10 anos (1999-2008) foi obtida objetivamente de dados de precipitação pentadais. O método dos compostos foi utilizado para obter a distribuição espacial de precipitação, temperatura da superfície do mar (TSM) e ventos à superfície a fim de verificar os fatores associados à variação de largura da ZCIT. Os resultados confirmaram os de trabalhos anteriores sobre a variabilidade da posição e apresentaram informações adicionais sobre a variabilidade da intensidade e largura. Na escala mensal, a largura e intensidade da ZCIT tendem a diminuir ao atingir as suas posições mais austrais (fevereiro, março e abril). A amplitude da variação anual foi de aproximadamente 7° de latitude para a posição média (de 1°N em abril a 8°N em agosto), de 3° para a largura (de 3° em março a 6° em outubro) e, quanto à intensidade da precipitação, foi de 3 mm.dia-1 (de 10 mm.dia-1 em março a 13 mm.dia-1 em julho). Na análise dos compostos da precipitação, TSM e divergência dos ventos à superfície na região do Atlântico Tropical, encontraram-se indícios de que, em condições de posição da ZCIT próxima à média, anomalias positivas de largura estariam associadas às de negativas de TSM e às positivas de convergência dos ventos à superfície, mas não houve significância estatística das diferenças.

This work presents an observational study of the Intertropical Convergence Zone (ITCZ) features over the central portion of the Atlantic Ocean. The Atlantic ITCZ position, width and intensity (mean precipitation) variability for 10 years (1999-2008) was obtained objectively from pentad precipitation data. The composite method was used to obtain of the spatial distribution of precipitation, sea surface temperature (SST) and surface winds in order to identify the factors associated with ITCZ width variation. The results confirmed previous works on ITCZ position variability and showed additional information concerning the variability of the intensity and width. At monthly timescale, the ITCZ width and intensity tend to decrease when ITCZ reaches its southernmost positions (February, March and April). The annual variation amplitude was about 7° of latitude for the mean position (1°N in April to 8°N in August), 3° for the width (3° in March to 6° in October) and 3 mm.day-1 for the precipitation intensity (10 mm.day-1 in March to 13 mm.day-1 in July). The composite analysis of precipitation, SST and surface winds divergence over the Tropical Atlantic region showed that, under conditions of ITCZ position close to the average, positive width anomalies would be related to negative SST anomalies and positive convergence of surface winds, but the differences had no statistical significance.

Foram realizadas mudanças no esquema de parametrização convectiva de Kain-Fritsch (KF2), para melhor representar a precipitação na região do Centro de Lançamento de Alcântara (CLA) em simulações com o modelo regional MM5. Simulações de 24 h em um domínio aproximadamente centrado no CLA, com espaçamento de grade de 30 km foram realizadas para o período de 2005-2006 (calibração) e 2008 (validação). O KF2 foi modificado sob a seguinte configuração: passo de tempo de 60 s, uso do esquema de convecção explícita warm rain e uso conjunto dos esquemas de convecção rasa de Grell e do KF2. As mudanças no KF2 foram: aumento da profundidade de nuvem necessária para disparar a convecção profunda e ajuste de alguns parâmetros da função disparo da convecção dependentes da velocidade vertical ascendente na coluna atmosférica. Com as modificações, houve expressiva melhoria na representação do total de precipitação e da fração dos dias do mês com chuva na escala mensal. O padrão espacial de erros no domínio, no entanto, não sofreu muitas alterações sobre o continente (em geral, a precipitação foi melhor representada sobre o continente do que sobre o oceano). Todas as etapas de mudanças e ajustes realizadas no trabalho poderão ser empregadas para melhorar a representação da precipitação em outras regiões específicas.

Changes in the Kain-Fritsch convective parameterization scheme (KF2) were included to better represent the precipitation in simulations using the MM5 regional model for the Alcântara Launch Center (CLA) region. Daily (24 h) integrations for a 30 km grid spacing domain centered in CLA were performed for 2005-2006 (calibration) and 2008 (validation). KF2 scheme was modified under the following simulation settings: time step of 60 s, use of warm rain scheme and joint use of Grell and KF2 shallow convection schemes. Changes in KF2 were: increase of minimum cloud depth to initiate deep convection and several trigger function parameters dependent on column upward vertical motion. With the changes, marked improvement in the representation of total precipitation and monthly fraction of rainy days was found. The spatial pattern of errors over the domain, however, did not show substantial changes (in general, precipitation was better represented over land than over ocean). The steps carried out in this work to change KF2 could be followed to improve the precipitation representation over other specific regions.

O Centro de Lançamento de Alcântara (CLA; 2° 22'S, 44º 23'W) tem papel importante para as atividades aeroespaciais no Brasil, sendo de interesse estudar os sistemas precipitantes atuantes sobre a região. O trabalho teve como objetivo caracterizar os sistemas associados aos eventos de precipitação ocorridos no CLA entre 2005 e 2006, utilizando totais horários de precipitação, dados de Reanálise do NCEP/NCAR, temperatura de brilho do satélite GOES-12 e radiação de onda longa emergente. Para tal, definiram-se critérios para identificar os sistemas meteorológicos de grande, meso e de escala local associados à precipitação no CLA. Os resultados apontaram que 40% dos eventos de precipitação estiveram associados a fatores de grande escala, destacando-se a Zona de Convergência Intertropical. Verificou-se que 60% (40%) dos eventos de precipitação se devem a processos estratiformes (convectivos). Os sistemas convectivos apresentaram as seguintes características: áreas entre 10(4) km² e 25x10(4) km², chuva posicionada na porção convectiva do sistema, intensificação por convecção diurna, inclusão em um sistema de escala maior e origem preferencial de sudeste ou nordeste. Os sistemas formados por processos estratiformes se subdividiram quase igualmente em dois grupos: resquícios de sistemas convectivos anteriormente atuantes no CLA e sistemas que não estão associados a nenhum processo convectivo.

The Alcântara Rocket Launching Center (CLA; 2° 22'S, 44º 23'W) plays an important role in aerospace research activities in Brazil, and so it is of interest to study the precipitation systems over the CLA region. This work aimed at characterizing the systems associated with precipitation occurrence at CLA from 2005 to 2006 by using hourly precipitation data, NCEP/NCAR Reanalysis data, brightness temperature data from GOES-12 satellite and outgoing longwave radiation data. Criteria were defined to identify large, meso and local scale meteorological systems associated with precipitation at CLA. About 40% of precipitation events were associated with large scale systems, mainly the Intertropical Convergence Zone, and about 60% (40%) of precipitation events are due to convective (stratiform) processes. The convective systems showed the following characteristics: area between 10(4) km² e 25x10(4) km², precipitation located in convective part of the system, intensification by diurnal convection, inclusion in a larger scale system and preferred southeasterly or northeasterly propagation. The systems formed from stratiform processes could be divided almost equally in two groups: reminder of convective systems previously active over CLA and systems that are not associated with any convective process.

Abstract: Climatological features of convective parameters (K index, IK; 950 hPa K index, IK950; Showalter index, IS; lifted index, ILEV; total totals index, ITT; and convective available potential energy, CAPE) derived from 12 UTC radiosounding data collected at the Alcântara Launch Center (CLA; 2°18'S, 44º22'W) from 1989 to 2008 were computed. The parameters IK, IK950, IS and ITT (ILEV and CAPE) showed a seasonal variation coherent (not coherent) to the annual cycle of precipitation. Interdaily variability was high all year round and was comparable to the monthly average seasonal variation. For IK and IK950, the monthly fraction of days with favorable conditions for precipitation occurrence (FRAC) showed good agreement with the monthly fraction of days with precipitation greater than 0.1 mm (PRP). For ITT and IS, the seasonal variation of FRAC was lower than the seasonal variation of PRP; for ILEV and CAPE, there were marked differences between FRAC and PRP. IK seasonal variation was primarily due to the presence of a deeper (shallower) low-level moist layer in the wet (dry) season. Among the studied convective parameters, the use of IK or IK950 for assessing precipitation occurrence was recommended.