Uma Revisão Qualitativa Enfatizando Aspectos Climáticos da Amazônia e da Região Nordeste do Brasil

O presente trabalho é uma revisão abordando diversos fatores físicos que afetam e definem o comportamento climático das regiões da Amazônia e do Nordeste do Brasil. Evidenciam-se as alterações que podem ser debitadas à presença e atuação do homem, em conjunção com as flutuações que a própria natureza impõe ao clima destas duas regiões em particular, como no caso da Oscilação Sul (El Niño e La Niña). Conclui-se com o entendimento de que é possível atuar de forma inteligente sobre o ambiente tropical sul-americano em favor do bem estar do mesmo homem que até agora foi agente destruidor. Contudo permanece o risco de que se ultrapasse o limiar que tornaria a degradação irremediável

INFLUÊNCIA DE ALGUNS PADRÕES DE TELECONEXÃO NA PRECIPITAÇÃO NO NORTE E NORDESTE DO BRASIL

Este estudo tem dois objetivos: (1) apresentar uma revisão sobre o que são teleconexões e a influência do fenômeno El Niño-Oscilação Sul (ENOS) e das anomalias de temperatura da superfície do mar (TSM) no oceano Atlântico Tropical no clima da América do Sul bem como (2) avaliar conjuntamente a influência das anomalias de TSM do Pacífico Tropical e do Atlântico Tropical na precipitação das regiões Norte e Nordeste do Brasil, assim como na posição e intensidade da Zona de Convergência Intertropical (ZCIT) no Atlântico. Entre os resultados é mostrado que nem sempre na ocorrência de El Niño há déficit de precipitação nas regiões Norte e Nordeste do Brasil, pois a influência das anomalias de TSM do Atlântico Tropical sul e¤ou norte se acopla ao efeito das anomalias de TSM do Pacífico Tropical, alterando ou fortalecendo o sinal das anomalias de precipitação sobre o Brasil tropical.

Atmosfera Versus Previsão do Tempo

The present work deals with the controversy between the human understanding of the behavior of real atmosphere and the weather prediction in response to numerical models. Themes like the Chaos Theory, Eulerian and Lagrangian models, and atmospheric waves are considered, reviewed and criticized.O presente trabalho aborda a dicotomia entre o entendimento do comportamento da real atmosfera por parte do homem e a resposta em termos de previsão do tempo proveniente de modelos numéricos. A Teoria do Caos, modelos Eulerianos e Lagrangeanos e ondas atmosféricas são temas abordados, revisados e criticados

INFLUÊNCIA DE ALGUNS PADRÕES DE TELECONEXÃO NA PRECIPITAÇÃO NO NORTE E NORDESTE DO BRASIL

Este estudo tem dois objetivos: (1) apresentar uma revisão sobre o que são teleconexões e a influência do fenômeno El Niño-Oscilação Sul (ENOS) e das anomalias de temperatura da superfície do mar (TSM) no oceano Atlântico Tropical no clima da América do Sul bem como (2) avaliar conjuntamente a influência das anomalias de TSM do Pacífico Tropical e do Atlântico Tropical na precipitação das regiões Norte e Nordeste do Brasil, assim como na posição e intensidade da Zona de Convergência Intertropical (ZCIT) no Atlântico. Entre os resultados é mostrado que nem sempre na ocorrência de El Niño há déficit de precipitação nas regiões Norte e Nordeste do Brasil, pois a influência das anomalias de TSM do Atlântico Tropical sul e¤ou norte se acopla ao efeito das anomalias de TSM do Pacífico Tropical, alterando ou fortalecendo o sinal das anomalias de precipitação sobre o Brasil tropical

An evaluation of the inter-hemispheric mass and humidity transport around South America

The global mass transport has a natural blocking in the Intertropical Convergence Zone that obstructs mass interchanges between the hemispheres. However there are some way out in this barrier and, consequently, a quantity of atmospheric mass is transferred from one hemisphere to the other along the year. The more known of these passages occurs during the Indian Monsoon period, when one observes significant mass transportation from Southern to Northern Hemisphere. This article has as objective to evaluate the meridional transport of mass and humidity, verifying the hypothesis of a possible inter-hemispheric flow in the South America troposphere and its oceanic surroundings, and also compare with the flow in other regions of the globe. For this evaluation it was used the mensal mean of meridional component of the wind and specific humidity in the period of 1984-2004, obtained from the NCEP/NCAR Reanalysis, with 2.5 x 2.5 latitude/longitude resolution. Initially the globe was divided in thee sectors: one between 120 W and zero meridian, another between zero meridian and 160 E and a third one from 160 E up to 120 W. These tree sectors were then divided in sub-sectors to facilitate the understanding of the regional inter-hemispheric mass transport. Some results may be summarized as: Relevant mean flow from Northern to Southern Hemisphere trough the South America continent, from November to March, mainly during the Southern Hemisphere summer. Great way out on the inter-hemispheric barrier with the flow coming from the Southern Hemisphere in Asia, mainly during the Northern Hemisphere summer. Meridional flow in South America apparently more intense than the Asian Monsoon one. Mean meridional flow from the Southern to Northern Hemisphere trough Mexico and Central America from May to November, mainly during the Northern Hemisphere summer. Relevant mean meridional flow from Northern to Southern Hemisphere, east of Africa (Madagascar) and east of Australia during Southern Hemisphere summer. Great way out on the inter-hemispheric barrier in Central Pacific Ocean, flowing from Northern Hemisphere between November to March, mainly in January and February. Humidity advection occurring trough equator to the subtropical region of South America during the Southern Hemisphere summer and to Central and North America during the Northern Hemisphere summer. Positive humidity advection along the year in the east of Africa region. Positive humidity advection from September to February in the east Australia region. Strong humidity advection from the Indian Ocean to the Asian Monsoon region during the Monsoon period. Significant humidity advection from the Amazonian region to the south in Brazil, Uruguay, Paraguay and northern Argentina during the Southern Hemisphere spring and summer, mainly from November to January.Pages: 991-99

Would be the Atmosphere Chaotic?

The atmosphere has often been considered “chaotic” when in fact the “chaos” is a manifestation of the models that simulate it, which do not include all the physical mechanisms that exist within it. A weather prediction cannot be perfectly verified after a few days of integration due to the inherent nonlinearity of the equations of the hydrodynamic models. The innovative ideas of Lorenz led to the use of the ensemble forecast, with clear improvements in the quality of the numerical weather prediction. The present study addresses the statement that “even with perfect models and perfect observations, the ‘chaotic’ nature of the atmosphere would impose a finite limit of about two weeks to the predictability of the weather” as the atmosphere is not necessarily “chaotic”, but the models used in the simulation of atmospheric processes are. We conclude, therefore, that potential exists for developments to increase the horizon of numerical weather prediction, starting with better models and observations

Anomalous rainfall in the Northeastern Brazil in January of 2004: downscaling using model WRF

Rainfall very above the historical average occurred in January 2004 over Northeast Brazil, bringing several upheavals to the population of the region, with material damages and loss of human lives. Although in its long-range forecasts in November and also in December of the 2003, the CPTEC global model had indicated positive precipitation anomalies for some sectors of Northeast Brazil in January 2004, the alert system was not set in motion with antecedence. As it is common to happen, the anomalous precipitation forecast underestimated the total rain actually observed in the region. Therefore the WRF mesoscale model was used in this study, fed with NCEP/NCAR reanalysis, in order to obtain a downscaling capable to refine the quantitative and space distribution of the precipitation in the region during January 2004, when the observed precipitation (about 400 mm/mouth) was four times superior the regional average for this month (about 100 mm/mouth). For a verification of the regional model ability in simulating the local precipitation, the same methodology was applied also for January 2005, showing that the total monthly rain in the region was around half of historical average (about 50 mm/mouth). The results show a regionalization of the simulated rain in Northeast Brazil compatible with the observations in January 2004. The forecasts of the CPTEC global model indicated highest rainfall over Maranhão State, westward of region where highest rainfall was actually observed (Ceará State), and the downscaling of WRF meet this result too. In the simulations for January 2005 the regional model coherently showed little precipitation in the region, as it really happened. The present study demonstrates the ability of WRF regional model to simulate the precipitation in continental tropical areas.Pages: 543-54

A SACZ event simulation using MM5 mesoscale model

SACZ are meteorological systems that bring great accumulation of rain in southeast and western regions of Brazil. The use of mesoscale model as a downscaling tool permits aggregate essential information as topography, vegetation cover and SST with high resolution. The SACZ event occurred in the period of January 22 to 27, 2004, was chosen to analyze the great quantity of precipitation that falls over an interesting basin in cerrado region of Brazil, the River Manso Basin. The MM5 mesoscale model was run with three grids, the first one covering the Brazilian area with 27 km of spacing, the second one with 9 km and the third one with 3 km, both centered on the Manso Basin. The 24 hours total precipitation simulated by the model showed great agreement with the totals of rainfall observed in the Brazilian rain gauge network. The punctual comparison between model simulation and observation shows in great details the atmospheric behavior, like temperature, relative humidity, wind speed and direction and precipitation. The accumulated rainfall evaluated in a meteorological station inside the Manso Basin during that SACZ event was 125 mm and the model simulation was 134 mm..Pages: 1171-117

Trajetórias cinemáticas aplicadas ao transporte no caso de vazamento de partículas radioativas para a atmosfera

Esta pesquisa é apresentada em duas etapas, a primeira corresponde à realização de algumas simulações numéricas utilizando como ferramenta dois modelos acoplados. A segunda objetivou demonstrar a importância da atmosfera na situação em que haja um vazamento hipotético de radionuclídeos para o meio ambiente, em especial na região da baixa troposfera, sendo a região estudada correspondente ao Complexo Nuclear de Angra dos Reis. Para realizar a modelagem numérica, o complexo nuclear foi considerado como uma fonte pontual no centro do domínio a ser estudado. Assim, no primeiro momento desse trabalho foi feita uma validação da metodologia, utilizando as partículas oriundas do vulcão Etna. Embora não fosse objeto de estudo as trajetórias de vulcões, este será considerado como uma fonte pontual e conseqüentemente um traçador natural. Na segunda etapa é feito um estudo de caso levando em consideração uma determinada situação sinótica previamente escolhida. As ferramentas são os dados de reanálises do National Centers for Environmental Prediction - NCEP, o modelo Regional Atmospheric Modeling System - RAMS, e o modelo de trajetórias cinemáticas desenvolvido na Universidade de São Paulo. É importante ressaltar que o conhecimento do comportamento da dinâmica da atmosfera associado com os deslocamentos das massas de ar, corresponde aos fatores principais para estudar os possíveis deslocamentos dos radionuclídeos, podendo alcançar a microescala, a mesoescala ou as escalas sinóticas

Coastal sea level response associated with frontal systems using conventional and NCEP/NCAR Reanalysis data, in Paranaguá Bay, Paraná State, Brazil

The main causes of the coastal sea level rising are the astronomical tides; however the effects of meteorological variables, also, are present in these variations. Frontal system associated with intense extra tropical cyclone reach the South Brazilian Coast in the 30° S and 50° W frequently. The objective of this work is to show these variations on South Atlantic coastal sea level in the Paranaguá Bay Paraná State - Brazil using meteorological series of conventional station and NCEP/NCAR Reanalysis data in the grid points on the interest oceanic area. It used a low-pass filter to remove the oscillations relative to the astronomical tide. Studies about the atmospheric driving forces were made through the statistical analysis in the time and frequency domain to know the lag time between the meteorological variables and the coastal sea level response to the occurrences of the low frequency atmospheric systems. To verify the local and remote influences in the entrance of the Paranaguá Bay, it was used hourly sea level records from the Wharf West in the Paranaguá Port and hourly average atmospheric pressure and wind from the Pontal do Sul station in the Paraná State in the 1997 to 1999 period. Atmospheric pressure and wind components of NCEP/NCAR Reanalysis grid points data in the domain from 25\ub0 S to 27\ub0 30' S and from the shoreline up to 45\ub0 W in the period from 1997 to 1998 was used too. The statistical treatment of the series allowed defining the maximum existing correlations in the physical process. In such way, we could know the response of the mean sea level associated with the frontal systems passage. The use of the NCEP/NCAR Reanalysis data selected on the oceanic area and the conventional station data near the tide gauge station made possible the comparison among the respective results. Thus, the relations between the atmospheric phenomena and the response of the coastal sea level are more evident with the information proceeding of the several points. The correlations found using the meteorological conventional and NCEP/NCAR Reanalysis data show the local and remote influences in this region. The frequency domain analysis with the conventional data shows greatest values of cross-spectral density for events around 5 day periods with coherence between 90 and 98%. This can be justified due to the proximity of both stations (tide gauge and meteorological station), both suffering local influences of the migratory atmospheric events. An important result that we could verify through the use by NCEP/NCAR Reanalysis data was how remote events affect coastal sea level in the entrance of this Bay. It was verified, mainly, on the southward Paranaguá Bay grid points, that the meridional wind component presents high-energy values, showing the influence of the coast direction in this local. Additionally, the Reanalysis data showed to be a very good information source for the South Atlantic Ocean where data gaps are still substantial, making possible to understand better some atmospheric events in the Brazilian Coast Region.Pages: 1883-189