Impacto da temperatura da superfície do mar na simulação da Zona de Convergência do Atlântico Sul

Durante o verão austral, diversas regiões do Brasil são afetadas por precipitação intensa, geralmente associada à Zona de Convergência do Atlântico Sul (ZCAS). O objetivo geral deste trabalho foi investigar a influência da resolução espacial e temporal dos dados de temperatura da superfície do mar (TSM) na simulação da precipitação associada à ZCAS. Foram realizadas simulações com o modelo BRAMS (Brazilian developments on the Regional Atmospheric Modeling System) para dois eventos de ZCAS, ocorridos em 1998 (El Niño) e 1999 (La Niña). A quantidade de precipitação acumulada na parte oceânica da ZCAS foi maior nos experimentos com TSM mais quente. Índices estatísticos foram utilizados para verificação do desempenho do modelo na simulação de precipitação nas regiões que compõem a ZCAS (oceânica, costeira e amazônica), com diferentes dados de TSM. A resolução espaço-temporal dos dados de TSM influencia de forma pouco significativa na representação da ZCAS pelo modelo BRAMS. O modelo é mais eficiente em identificar a ocorrência/não ocorrência de chuva do que em localizar núcleos mais intensos e seu desempenho foi superior (inferior) na região amazônica (oceânica) da ZCAS.FAPESP - Processo n. 2007/57101-2CNPqCAPES - PROE

Analysis of surface wind simulated by WRF model in Rio de Janeiro (RJ) during August 2012

The region of Baia de Guanabara (RJ), bordered by the city of Rio de Janeiro,\ud will host the Olympic Games in August 2016. Sailing races are highly dependent on\ud surface wind conditions. This region is surrounded by hills, cities, forest and open\ud sea areas, which generates special local circulations. Thus, the flows on the surface,\ud caused by the combination of different types of local circulations and synoptic scale\ud circulations were studied from data recorded in four surface meteorological stations\ud located nearby this region and compared with models simulations. There are two\ud stations located at airports, Galeão (SBGL) and Santos Dumont (SBRJ), which\ud border the bay, and two stations located far from the bay, but inside the metropolitan\ud region of Rio de Janeiro, Jacarepagua (A654) and Vila Militar (A621), both supported\ud by INMET. The regional model WRF was configured to 27, 9 and 3km grid spacing and\ud then compared to the global model GFS. Results from 31 simulations (every day from\ud August 2012) of 72h forecast data from WRF-9km, WRF-3km and GFS model were\ud interpolated to the latitudes and longitudes of the four stations for calculating the\ud mean error and the root mean square error of each model at each station place.\ud At A621, A654 and SBRJ, the increased resolution of the limited area model provided\ud better results, probably because the complexity of topography and the shape of the urban and\ud the bay area. At SBGL, WRF-9km provided similar results to WRF-3km but better than the GFS.\ud It happens because GFS doesn't have enough resolution to simulate the bay effect on the surface\ud wind. Although the GFS showed worse results at A654 than WRF-3km, it was better than\ud WRF-9km, probably due to the bad representation of two hills nearby this station (Maciço\ud da Pedra Branca e Maciço da Tijuca) on 9km topography resolution. It makes the WRF-9km\ud overestimate the east wind at this station. Both GFS and WRF-9km underestimate the south wind\ud at A654.FAPESPFAPERJCNP

Relationship between large-scale atmospheric circulation and interannual\ud variability of extreme events of sea ice in the Antarctic Dipole

The Antarctic sea ice plays an important role in the global climate system due to its\ud high albedo, low thermal conductivity, influence on the position of the storrn tracks, forrning\ud water masses and air masses. Some studies suggest that the Pacific-South America (PSA),\ud pattem more directly related to the variability of the EI Nino Southem Oscillation (ENSO),\ud has a greater influence on the sea ice in the interannual timescale on the region of the\ud Antarctic Dipole (ADP), located in the central/eastem Pacific and South Atlantic. Thus, the\ud objective of this study was to analyze the influence of large-scale atmospheric circulation on\ud the interannual variability of extreme events of sea ice in the ADP region. We used the ERAInterim\ud reanalysis (ECMWF Data Server) and the sea ice extent from the National Snow and\ud Ice Data Center (University of Colorado) for the sectors of the Bellingshausen-Arnundsen\ud Seas (BAS, 130° W to 60° W) and Weddell Sea (WS, 60° W to 20° E). The time series (1989-\ud 2007) were filtered on interannual timescale (> 370 days). For the austral winter the extremes\ud were defined using the first (q25) and third (q75) quartile ofthe distribution ofinterannual sea\ud ice anomalies. Below the q25 were considered extremes negative of sea ice (ENSI) and above\ud the q75 extremes positive (EPSI). Lastly composites were lagged in time for the interannual\ud anomalies of atmospheric fields, considering 365 days prior and subsequent to ENSIIEPSI.\ud Statistical significance was obtained with the Student's t test, at 10%. The positive anomalies\ud of air temperature at 2 meters over the equatorial Pacific are associated with positive\ud anomalies of SLP/geopotential at 500 hPa (GE0500) on the BAS/southeast of the South\ud Pacific, which are part of the wave train between middle and high latitudes of the Southem\ud Hemisphere, similar to the PSA pattem. Thus, there is an intensification of the northerly\ud winds at low levels on the BAS, contributing to the heating/ENSI. Simultaneously, there is a\ud weakening of northerly winds over the region of WS, leading to negative enomalies of air\ud temperature/EPSI. This configuration is observed since the lag = 365 days. On the other hand,\ud when there is cooling in the region of the equatorial Pacific, anomalies of SLP/GE0500 on\ud the BAS/southeastem South Pacific are negative. Therefore, there is a weakening of the\ud northerly winds and thus negative anomalies of air temperature/EPSI. At the sarne time, on\ud the WS there is an intensification of the northerly winds, contributing to the positive\ud anomalies of air temperaturelENSI. As the ENSO signal persists for about two seasons,\ud changes in sea ice are amplified and persistent even after two to four seasons ofENSO. Thus,\ud ENSI (EPSI) in BAS and EPSI (ENSI) in WS are associated with the wave train similar to the\ud PSA pattem during warm (cold) ENSO. These results are in agreement with previous studies.Título: V SIC: Interação oceano-atmosfera: impactos climáticos no presente e cenários futuros. Eventos simultâneos ao V SIC: Encontro Sul Brasileiro de Meteorologia, 5. Florianópolis, Brasil, 2013; Congresso Latino-Americano e Ibérico de Meteorologia da FLISMET, Florianópolis, Brasil, 2013

Interannual and Intraseasonal Variations of the Onset and Demise of the Pre-Wet Season and the Wet Season in the Northern Northeast Brazil

Abstract The Northern Northeast Brazil (NNB) has two rainy periods, namely Pre-Wet Season (PWS) and Wet Season (WES), which are usually treated as one system. The precipitation pattern on NNB is influenced by sea surface temperature (SST) anomalies in the Atlantic and Pacific Ocean on interannual timescales particularly by the Interhemispheric Gradient of SST anomalies (IGS) and El Niño Southern Oscillation (ENSO). On intraseasonal time scales, the MJO is especially important. This study investigates the variability of the PWS/WES. The PWS is largely associated with the development of the South America Monsoon System and South Atlantic Convergence Zone (SAMS/SACZ); the onset is depicted by incursion of the SAMS/SACZ northward. Anomalous atmospheric cyclonic circulation over the southeastern Brazil along with easterlies over the northern Tropical Atlantic marks the early onset of the PWS, while easterlies over the southern Tropical Atlantic are related to late onset episodes. The demise of the PWS is significantly associated with propagation of the MJO, specifically during phases 4-5 of the MJO lifecycle. A Rossby wave train in 200-hPa geopotential height with positive anomalies over central-southern Brazil is depicted during transition between PWS and WES

Clouds, rain and biosphere interactions in Amazon

A review of results obtained within the Physical Climate component of LBA with respect to the interaction between the biosphere and cloud and rain formation in the Amazon Basin, in different seasons and different regions within the Basin is presented. The deforestation effect and the effect of biomass burning are discussed and the physical processes highlighted based on the data collected in several LBA intensive field campaigns. The complex interactions and the progress in the understanding their evolution based on the new datasets is presented.Apresenta-se uma revisão dos resultados já obtidos no Projeto LBA, na componente de Física do Clima, referente ao efeito da interação entre a biosfera e a formação de nuvens e de chuva em diferentes estações do ano e regiões da Bacia Amazônica. O efeito do desmatamento e das queimadas na atmosfera é abordado assim como mecanismos atmosféricos que foram caracterizados a partir das diversas campanhas do projeto LBA. Uma visão da complexidade das interações e do progresso que tem sido feito com base nos dados colhidos é apresentada.COHEN, J. C. P. Universidade Federal do Par

High resolution simulation of low level jets in the eastern Amazonia

An important research domain is referred to the forest-atmosphere interaction, since the flow in the region immediately above the vegetation is complex and has characteristics still not well known. One of these characteristics is the existence, in some situations, of relative maxima in the wind velocity vertical profiles, the low level jets (LLJ), in regions less than 1 km distant from the surface. They may contribute to intensify the mixture in the surface and in the region where they occur. It is possible that the presence of such phenomenon introduce additional difficulties in the parameterization of the forest-atmosphere exchange processes. Therefore, it is entirely reasonable the study of LLJs in order to determine the conditions of their occurrence and to investigate the consequences of their existence in the characteristics of the Nocturnal Boundary Layer (NBL) structure near the surface. The data were collected during the Field Experiment called CiMeLA (Mesoscale Circulations in the Eastern Amazonia), from October 27 to November 17 of 2003, in the Forest Reserve of Caxiuanã, Pará. During this Experiment, the measurements were vertical soundings of the atmosphere with radiosondes, launched at four different times per day (06, 12, 18, 00 UTC), except in the last three days of the Experiment, when there were soundings in every 3 hours (keeping the times above). BRAMS (Brazilian developments on the Regional Atmospheric Modeling System) was used to evaluate the origin of the LLJ. The numerical simulations presented contained 3 nested grids with a horizontal spacing of 45, 15 and 5 km. The models initialization was variable, each 6 hours, with the analysis of CPTECs global model, the radiosondes and surface data. The simulation used the models of surface and vegetation, radiation, cloud microphysics, deep convective parameterization of Grell and shallow convection parameterization. The numerical simulations with this high resolution model indicated the occurrence of low level jets, nevertheless it did not reproduce in detail some of the observed characteristics of the flow. It generated both LLJs of November 13 and 14 at 06 UTC. However, their magnitude was about 2 and 3 m/s lower and their height was higher than what was observed. Another interesting result was that the equivalent potential temperature indicated the arrival of thermodynamically different air possibly associated to the LLJ. An important aspect revealed by the simulations with BRAMS was the origin of the jets, which is associated to a phenomenon of canalization of the flow above zones where there are some of the great rivers in the Northeast of Pará.Pages: 1733-174

Variabilidade espacial e temporal da precipitação observada com o radar na confluencia do Tapajós e Amazonas

Standard Amazonian rainfall climatologies rely on stations preferentially located near river margins. River breeze circulations that tend to suppress afternoon rainfall near the river and enhance it inland are not typically considered when reporting results. Previous studies found surprising nocturnal rainfall maxima near the rivers in some locations. We examine spatial and temporal rainfall variability in the Santarém region of the Tapajós-Amazon confluence, seeking to describe the importance of breeze effects on afternoon precipitation and defining the areal extent of nocturnal rainfall maxima.We used three years of mean S band radar reflectivity from Santarém airport with a Z-R relationship appropriate for tropical convective conditions. These data were complemented by TRMM satellite rainfall estimates. Nocturnal rainfall was enhanced along the Amazon River, consistent with the hypothesis that these are associated with the passage of instability lines, perhaps enhanced by local channeling and by land breeze convergence. In the daytime, two rainfall bands appear in mean results, along the east bank of the Tapajós River and to the south of the Amazon River, respectively.Na Amazônia as series climatológicas estão baseadas na rede de estações meteorológicas de superfície que estão instaladas preferencialmente nas margens de rios. Portanto, o efeito de brisas fluviais que promovem precipitação no interior do continente não está sendo contabilizado nas medidas realizadas nestas estações. Além disto, estudos anteriores encontraram máximo de precipitação no período noturno sobre rios. Assim, este artigo examina a variabilidade espacial e temporal da precipitação na região de confluência dos rios Tapajós e Amazonas em Santarém, visando descrever a importância da brisa fluvial na distribuição da precipitação durante a tarde e definir a extensão da área onde ocorre maxima precipitação no período noturno. A refletividade medida pelo radar meteorológico banda S, instalado em Santarém para um período de três anos foi utilizada, tendo estes dados sido calibrados através dos dados do sensor de precipitação instalado abordo do satélite TRMM. A intensidade de precipitação foi estimada utilizando a relação ZR para o caso convectivo tropical. No período noturno, a máxima precipitação foi encontrada ao longo do rio Amazonas, consistente com a hipótese de que esta precipitação estaria associada a passagem das linhas de instabilidade neste período, talvez esta precipitação também esteja sendo reforçada pela canalização do rio e pela confluência do vento de retorno da brisa fluvial durante a noite. Para o período diurno, observou-se duas bandas de precipitações localizadas no interior do continente, uma ao longo da margem leste e outra ao sul dos rios Tapajós e Amazonas, respectivamente

Intradiurnal variability of soil temperature, heat flux, and soil thermal diffusivity in different ecosystems in eastern Amazonian

Heat and moisture exchanges between the ground surface and the atmosphere are frequently dominant driving mechanisms for mesoscale circulations. These surface processes depend on the soil and surface characteristics, thus presenting spatial variation. Over land, significant diurnal changes of temperature and moisture balance near the interface with the atmosphere also occur. So, coupled models of heat and moisture transport in the soils near its surface require information about soil thermal properties, which are used to determine temperature profiles and heat flux in the soil. In particular over the Amazon region, a vast area has been changed into pasture or agricultural land, a change that produces significant alterations in the soil-vegetation-atmosphere interactions and, consequently, in the weather and climate. In the present work, the intradiurnal variability of soil temperature, heat flux and moisture content in eastern Amazonian are analyzed. The thermal diffusivity is iteratively obtained through a numerical solution of the heat conduction equation using soil temperature series. The measurements were collected within the Milênio-LBA program - Subproject UFPA, during the experiment CiMela ("Mesoscale Circulations in Amazonian East"), held during the dry period of 2003 in different ecosystems of the Pará State: (i) forest (Caxiunã Reserve, Melgaço - 01°42'30''S; 51°31'45'' W); (ii) pasture (Soure, Marajó Island); (iii) natural mangrove (Tracuateua Island, Bragança ); (iv) degraded mangrove (Tracuateua Island, Bragança); and (v) agricultural area (Fazenda Escola da Universidade Federal Rural da Amazônia, Igarapé Açu)