Estabilidade e estrutura da turbulência sob a influência de jatos de baixos níveis noturnos no sudoeste da amazônia

The aim of this study was to evaluate how the occurrence of nocturnal Low Level Jets (LLJs) may influence the atmospheric turbulence structure and atmospheric stability at the surface. Using data collected from both radiosondes and Eddy Covariance Systems during the WetAMC-LBA campaign, three atmospheric stability regimes were defined at the surface: weakly stable; transition, and very stable. Relating these regimes and the turbulence structure of strong, weak-type 1 (occurring above 500 m) and weak-type 2 (occurring below 500 m) LLJs, it was observed that 22% of the strong LLJ cases were within the weakly stable regime, whereas only 3% of the weak LLJ cases (type 1 and 2) were in this regime. Another interesting result is that in the weak type 1 LLJ cases, the highest percentage were within the very stable regime (approximately 54%). During strong-LLJs, mean friction velocity and mean turbulence kinetic energy were 0.09 ms-1 and 0.13 m2s-2, respectively. For weak-type 1-LLJs, these variables presented respectively values of 0.04 ms-1 and 0.02 m2 s-2, whereas for weak-type 2-LLJs values were 0.06 ms-1 and 0.03 m2s-2, respectively. These results suggest that LLJs with sufficiently high velocities may increase turbulence and introduce weak atmospheric stability at near surface, depending on the height of occurrence. © 2015, Sociedade Brasileira de Meteorologia. All rights reserved

Concentração e fluxo de CO2 sobre o reservatório hidrelétrico de Balbina (AM)

The reservoir Balbina (59º 28’ 50w, 1º 53’ 25” S), located near the city of Manaus, Amazonas, in Central Amazônia, Brazil, is the second largest hydroelectric reservoir in an area located in the Amazon Basin. In this reservoir, CO2 measurements were performed at high frequency (10 Hz), CO2 flux with gas analyzer infrared (IRGA) coupled to a floating chamber and meteorological variables with a buoy instrumented to 2 m from the lake surface. The average CO2 concentration was 392 and 426 ppm for the day and night, respectively, and the daily average emission rate was 40.427±24.040 μmol-1.m-2.d-1. The accumulation of CO2 in the lake overnight, beyond respiration, shows to be affected by low wind speeds, waterside convection, physical processes involving high concentrations of CO2 for the surface and the presence of land breeze. The fluxes show no statistically significant difference with the meteorological variables and were considerably lower than a previous study for the same lake. However, the values are in agreement with other studies in Amazonian tropical lakes and other reservoirs. © 2017, ABES - Associacao Brasileira de Engenharia Sanitaria e Ambiental. All rights reserved

Variáveis hidroclimáticas associadas com eventos de El-Niño e La-Niña no reservatório hidrelétrico de Curuá-Una, Amazônia Central

The anomalies of Sea Surface Temperature (SST) influence rainfall and therefore the regime of the rise and fall in the level of the rivers in the Amazon region. The aim of this study was to investigate the influence of the El Nino-Southern Oscillation (ENSO) on hydroclimatic variables and identify the existence of trends on these variables in the Curuá-Una hydroelectric reservoir in the West of the State of Pará. It was used 27 years of monthly precipitation and water flow data to identify possible trends using a non-parametric test (Mann Kendall, p<0.05), and the standardized precipitation index (SPI) was also calculated. The results indicate a positive tendency of the influence of the ENSO on hydroclimatic variables, although it was observed that the rainfall did not increase over the period of 1977 to 2004. The SPI indicates that extreme events of precipitation are related to El Nino and La Nina and that lower precipitation periods were more intense in the decades of the 80´s and 90’s. The results show that El Nino events can directly affect the water balance at the micro-watershed of Curuá-Una, as was observed in 2015. © 2016, Instituto Nacional de Pesquisas da Amazonia. All rights reserved

Medições por Covariância de Vórtices Turbulentos dos Fluxos de Calor Latente, Sensível, Momentum e co2 sobre o Reservatório da Usina Hidrelétrica de Curuá-una – PA

Flux measurements of latent heat, sensible heat, momentum, and CO2 were performed from 15 to 26 June 2015 on the reservoir of the hydroelectric plant Curuá-Una (PA). The flux system is located upstream of the main channel of the reservoir and installed at 3 m above the water surface on a floating structure. The hydroelectric plant Curuá-Una was the first plant built in the Amazonia and it is in operation for almost 40 years. During installation, the vegetation around the river channel was not removed, which led to large emissions of greenhouse gases into the atmosphere. The wind speed was important to maintain turbulent mixing mechanically. Latent heat flux showed significant correlation with the wind velocity (r = 82%). As a result of the combined effect of turbulent mixing generated thermally and mechanically, the latent and sensible heat fluxes were positive throughout the investigation period and the atmospheric surface layer remained unstable. The CO2 flow was predominantly negative (84%), characterizing the reservoir as a CO2 sink.Medidas dos fluxos de calor latente, sensível, momentum e CO2 foram realizadas no período de 15 a 26 de junho de 2015 sobre o reservatório da Usina Hidrelétrica de Curuá-Una (PA). O sistema de fluxo está localizado a montante do canal principal do reservatório com altura de 3 m acima da superfície da água, instalado em uma estrutura flutuante. A Usina Hidrelétrica de Curuá-Una foi a primeira usina construída na Amazônia e está em funcionamento a quase 40 anos. Durante sua instalação, a vegetação ao redor do canal do rio não foi retirada, o que levou a grandes emissões de gases de efeito estufa para atmosfera. A velocidade do vento foi considerável para manter uma mistura turbulenta mecanicamente. O fluxo de calor latente apresentou correlação significativa com a velocidade do vento (r = 82%). Como consequência do efeito combinado da mistura turbulenta gerada termicamente e mecanicamente os fluxos de calor latente e sensível foram positivos durante todo o período investigado e a camada superficial atmosférica manteve-se instável. O fluxo de CO2 foi dominantemente negativo (84%) caracterizando o reservatório como sumidouro de CO2

Avaliação da habilidade do modelo WRF em representar a precipitação na amazônia usando diferentes escalas

Precipitation over the northern Amazon during the austral summer and autumn seasons of the 1988-1999 was simulated using the Regional Weather Research and Forecasting (WRF) model, with downscaling approach with nested domains of 45 and 15 km. The boundary and initial conditions were obtained from the Climate Forecast System Reanalysis (CFSR) of the National Centers for Environmental Prediction (NCEP). The model skill was tested using different rea-nalyzed precipitation datasets that represent different space scales. The bias of the model shows seasonal and spatial dependences, with positive bias in southwestern Brazilian Amazon during summer and in northwestern South America during autumn. The downscaling was needed to reproduce the surface influences on the regional and local systems that affect the rainfall distribution in the region. The WRF model, in general, reproduces the main observed precipitation patterns, without the dry bias, typical of general circulation models (GCM). The results indicate that the dynamic downscaling technique improves the WRF model performance for the seasonal climate forecast in the Amazon region. © 2019, Sociedade Brasileira de Meteorologia. All rights reserved

Características Médias do Vento acima e abaixo do Dossel da Floresta durante o Goamazon em um Sítio Experimental na Amazônia

The aim of this study was to evaluate the temporal evolution of average characteristics of the vertical profiles of speed and direction above and within of the forest canopy at the Cuieiras experimental site, located about 100 km from the Manaus, Amazonas state, Brazil. We used about 10 months of half-hourly averaged data from 10 sonic anemometers installed at different levels above and within the forest canopy during GoAmazon project in 2014. We found that the vertical wind speed profile varied with the various layers above and below the forest canopy, describing an S-shape type, a form determined by physical obstructions imposed by vertical heterogeneity of the canopy. The predominant wind directions were not constant with height, suggesting that very local circulations can influence the subcanopy flow.O objetivo deste trabalho foi avaliar as características médias da evolução temporal do perfil vertical da velocidade e direção do vento acima e abaixo do dossel da floresta no sítio experimental do Cuieiras, localizado cerca de 100 Km da cidade Manaus, estado do Amazonas, Brasil. Para tanto, foram utilizados aproximadamente 10 meses de dados de 10 anemômetros sônicos instalados em diferentes níveis acima e abaixo do dossel da floresta, durante o projeto GoAmazon, no ano de 2014 . Analisando o conjunto de dados, por meio de médias para cada 30 minutos diários de todo período estudado, foi possível observar que o perfil vertical da velocidade do vento varia de acordo com as diferentes camadas acima e abaixo do dossel da floresta e possui uma forma tipo “S”, definida pelas obstruções físicas impostas pela heterogeneidade vertical da floresta. As direções predominantes do vento não são constantes com a altura, sugerindo que circulações locais podem influenciar o escoamento no sítio experimental estudado

An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08)

The Amazon Basin provides an excellent environment for studying the sources, transformations, and properties of natural aerosol particles and the resulting links between biological processes and climate. With this framework in mind, the Amazonian Aerosol Characterization Experiment (AMAZE-08), carried out from 7 February to 14 March 2008 during the wet season in the central Amazon Basin, sought to understand the formation, transformations, and cloud-forming properties of fine- and coarse-mode biogenic aerosol particles, especially as related to their effects on cloud activation and regional climate. Special foci included (1) the production mechanisms of secondary organic components at a pristine continental site, including the factors regulating their temporal variability, and (2) predicting and understanding the cloud-forming properties of biogenic particles at such a site. In this overview paper, the field site and the instrumentation employed during the campaign are introduced. Observations and findings are reported, including the large-scale context for the campaign, especially as provided by satellite observations. New findings presented include: (i) a particle number-diameter distribution from 10 nm to 10 Î1/4m that is representative of the pristine tropical rain forest and recommended for model use; (ii) the absence of substantial quantities of primary biological particles in the submicron mode as evidenced by mass spectral characterization; (iii) the large-scale production of secondary organic material; (iv) insights into the chemical and physical properties of the particles as revealed by thermodenuder-induced changes in the particle number-diameter distributions and mass spectra; and (v) comparisons of ground-based predictions and satellite-based observations of hydrometeor phase in clouds. A main finding of AMAZE-08 is the dominance of secondary organic material as particle components. The results presented here provide mechanistic insight and quantitative parameters that can serve to increase the accuracy of models of the formation, transformations, and cloud-forming properties of biogenic natural aerosol particles, especially as related to their effects on cloud activation and regional climate. © 2010 Author(s)

The Amazon Tall Tower Observatory (ATTO): Overview of pilot measurements on ecosystem ecology, meteorology, trace gases, and aerosols

The Amazon Basin plays key roles in the carbon and water cycles, climate change, atmospheric chemistry, and biodiversity. It has already been changed significantly by human activities, and more pervasive change is expected to occur in the coming decades. It is therefore essential to establish long-term measurement sites that provide a baseline record of present-day climatic, biogeochemical, and atmospheric conditions and that will be operated over coming decades to monitor change in the Amazon region, as human perturbations increase in the future. The Amazon Tall Tower Observatory (ATTO) has been set up in a pristine rain forest region in the central Amazon Basin, about 150 km northeast of the city of Manaus. Two 80 m towers have been operated at the site since 2012, and a 325 m tower is nearing completion in mid-2015. An ecological survey including a biodiversity assessment has been conducted in the forest region surrounding the site. Measurements of micrometeorological and atmospheric chemical variables were initiated in 2012, and their range has continued to broaden over the last few years. The meteorological and micrometeorological measurements include temperature and wind profiles, precipitation, water and energy fluxes, turbulence components, soil temperature profiles and soil heat fluxes, radiation fluxes, and visibility. A tree has been instrumented to measure stem profiles of temperature, light intensity, and water content in cryptogamic covers. The trace gas measurements comprise continuous monitoring of carbon dioxide, carbon monoxide, methane, and ozone at five to eight different heights, complemented by a variety of additional species measured during intensive campaigns (e.g., VOC, NO, NO2, and OH reactivity). Aerosol optical, microphysical, and chemical measurements are being made above the canopy as well as in the canopy space. They include aerosol light scattering and absorption, fluorescence, number and volume size distributions, chemical composition, cloud condensation nuclei (CCN) concentrations, and hygroscopicity. In this paper, we discuss the scientific context of the ATTO observatory and present an overview of results from ecological, meteorological, and chemical pilot studies at the ATTO site. © Author(s) 2015

On the temporal scale of the turbulent exchange of carbon dioxide and energy above a tropical rain forest in Amazonia

The Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) project has been using the eddy covariance technique since 1998 to monitor energy, water, and carbon surface fluxes over Amazonia. The results obtained up-to-date indicate high level of uncertainties, especially regarding the role of the Amazonian ecosystem to the global carbon budget. Besides the problems related to the eddy covariance measuring system (systematic error and nighttime stable conditions), an extremely important factor is associated with the averaging time scale or "time window" used by the scientific community to determine the surface fluxes. This work presents initial efforts to determine the turbulence time scale for long-term carbon and energy surface fluxes over the Amazon rain forest. A total of 198 nights and 218 days during 2006 were analyzed. The multiresolution decomposition technique was applied to project the signal into several time scales and determine when the spectral and cospectral gap occurred. This technique permitted evaluating and separating the real contribution from turbulent and mesoscale fluxes to the total surface fluxes at both diurnal and nocturnal periods. The average turbulence time scale was below 200 and 1200 s for all scalars at nighttime and daytime, respectively. In all cases, there is seasonal dependence. This result shows that the time scale commonly used to calculate nocturnal surface fluxes (30 min) includes a good portion of mesoscale flux in the estimates. The role of these mesoscale fluxes, in terms of seasonal dependence and the uncertainties they add to the estimates, is then analyzed. Copyright 2009 by the American Geophysical Union

Relação entre O3 troposférico e CO sobre área de pastagem a partir de sondagens do satélite ambiental AQUA

Relationships between the estimates of tropospheric ozone (O3) and carbon monoxide (CO), mainly from biomass burn and changes in land use of one region of Brazil, were studied using observational analysis from the AQUA plataform from 2003 to 2010. The objective of this research was to study the variability of tropospheric O3 concentration and its relationship with the variability of CO concentration. It was studied in an area of pasture (square of 5° x 5°), located in SinopMT. The results suggest that the O3 concentrations are increased by the increase of CO concentrations during dry season, when it is observed the increasing of outbreaks of fires. Fires are frequent and are associated to changes in land use for activities of agriculture and cattle, and its dynamic is modulated by the climatology of precipitation. Moreover, the intensity of fires is defined by extreme climatic events associated to ENOS. The seasonality occurs for both gases series (CO and O3) as for the series of precipitation and fires. Analyses of coherence and phase between series of CO and O3 suggest a moderate to strong relationship between the variables for different time scales. For a time scale from 0.25 year to one year (three months to one year), the flux of CO first occurs that O3 flux with no phase difference for all years of the study, which suggests that the increasing of CO concentrations causes increasing of O3. These results suggest that CO concentrations are incremented during periods of fire and then, consequently, produce O3. In this context, the use of remote tools (e.g. remote sensing) to understand the dynamic of gases in relation to fires is central to develop models of air quality and polution monitoring.Pages: 1930-193