Gilberto Fisch

Overview of the inorganic and organic composition of size-segregated aerosol in Rondônia, Brazil, from the biomass-burning period to the onset of the wet season

The aerosol characterization experiment performed within the Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) field experiment carried out in Rondonia, Brazil, in the period from September to November 2002 provides a unique data set of size-resolved chemical composition of boundary layer aerosol over the Amazon Basin from the intense biomass-burning period to the onset of the wet season. Three main periods were clearly distinguished on the basis of the PM10 concentration trend during the experiment: (1) dry period, with average PM10 well above 50 mu g m(-3); (2) transition period, during which the 24-hour-averaged PM10 never exceeded 40 mu g m(-3) and never dropped below 10 mg m(-3); (3) and wet period, characterized by 48-hour-averaged concentrations of PM10 below 12 mu g m(-3) and sometimes as low as 2 mu g m(-3). The trend of PM10 reflects that of CO concentration and can be directly linked to the decreasing intensity of the biomass- burning activities from September through November, because of the progressive onset of the wet season. Two prominent aerosol modes, in the submicron and supermicron size ranges, were detected throughout the experiment. Dry period size distributions are dominated by the fine mode, while the fine and coarse modes show almost the same concentrations during the wet period. The supermicron fraction of the aerosol is composed mainly of primary particles of crustal or biological origin, whereas submicron particles are produced in high concentrations only during the biomass-burning periods and are mainly composed of organic material, mostly water-soluble, and similar to 10% of soluble inorganic salts, with sulphate as the major anion. Size-resolved average aerosol chemical compositions are reported for the dry, transition, and wet periods. However, significant variations in the aerosol composition and concentrations were observed within each period, which can be classified into two categories: (1) diurnal oscillations, caused by the diurnal cycle of the boundary layer and the different combustion phase active during day (flaming) or night (smouldering); and (2) day-to-day variations, due to alternating phases of relatively wet and dry conditions. In a second part of the study, three subperiods representative of the conditions occurring in the dry, transition, and wet periods were isolated to follow the evolution of the aerosol chemical composition as a function of changes in rainfall rate and in the strength of the sources of particulate matter. The chemical data set provided by the SMOCC field experiment will be useful to characterize the aerosol hygroscopic properties and the ability of the particles to act as cloud condensation nuclei.

Uma revisão geral sobre o clima da Amazônia

Este trabalho busca apresentar, de uma maneira compacta, os principais resultados cientificos ja alcancados pela comunidade brasileira e mundial sobre pesquisas na Amazonia. Aborda-se o paleoclima da regiao, bem como as caracteristicas atuais, em termos de temperatura do ar e da distribuicao de chuvas. Sao discutidos os principais sistemas atmosfericos atuantes na regiao, tais como linhas de instabilidade, brisa fluvial, teleconexoes com El-Nino, interacao com sistemas frontais no sul do pais, friagens, alem da variabilidade do clima nas escalas interanuais e de longo-prazo. Tendo em vista as altas taxas de desmatamento em algumas partes da Amazonia, sao discutidos as principais modificacoes microclimaticas e resultados obtidos por simulacoes numericas devido a substituicao de floresta tropical por areas de pastagens. Finalizando, e apresentado um resumo dos varios experimentos micrometeorologicos que ocorreram na Amazonia nas ultimas duas decadas.

Transpiration from an Amazonian rainforest calculated from stomatal conductance measurements

Abstract A multi-layer combination equation has been used to calculate transpiration from a tropical rainforest in the central Amazon, Brazil. The five-layer formulation used through-canopy measurements of temperature and humidity deficit with leaf stomatal and boundary layer conductances scaled up to canopy layer values used a profile of canopy leaf area index derived from the literature. Net radiation input to each layer was estimated from an above canopy measurement using an extinction function and leaf area index. Transpiration calculated for hourly and daily periods in a range of seasonal conditions agreed well with those measured directly with an eddy correlation device. Four simplified forms of the transpiration calculation were also compared with the direct measurement. These simplified forms used the above-canopy or the average of the through-canopy values of weather variables and used either the average of leaf conductances multiplied by total leaf area index or the average of the layer conductances. These simplified forms of the transpiration calculation gave poorer agreement with measured transpiration.

The Chuva Project: How Does Convection Vary across Brazil?

CHUVA, meaning “rain” in Portuguese, is the acronym for the Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud-Resolving Modeling and to the Global Precipitation Measurement (GPM). The CHUVA project has conducted five field campaigns; the sixth and last campaign will be held in Manaus in 2014. The primary scientific objective of CHUVA is to contribute to the understanding of cloud processes, which represent one of the least understood components of the weather and climate system. The five CHUVA campaigns were designed to investigate specific tropical weather regimes. The first two experiments, in Alcantara and Fortaleza in northeastern Brazil, focused on warm clouds. The third campaign, which was conducted in Belem, was dedicated to tropical squall lines that often form along the sea-breeze front. The fourth campaign was in the Vale do Paraiba of southeastern Brazil, which is a region with intense lightning activity. In addition to contributing to the understanding of clo...

On the influences of the El Niño, La Niña and Atlantic dipole pattern on the Amazonian rainfall during 1960-1998.

The influence of the large-scale climatic variability dominant modes in the Pacific and in the Atlantic on Amazonian rainfall is investigated. The composite technique of the Amazon precipitation anomalies is used in this work. The basis years for these composites arc those in the period 1960-1998 with occurrences of extremes in the Southern Oscillation (El Nino or La Nina) and the north/south warm (or cold) sea surface temperature (SST) anomalies dipole pattern in the tropical Atlantic. Warm (cold) dipole means positive (negative) anomalies in the tropical North Atlantic and negative (positive) anomalies in the tropical South Atlantic. Austral summer and autumn composites for extremes in the Southern Oscillation (El Nino or La Nina) and independently for north/south dipole pattern (warm or cold) of the SST anomalies in the tropical Atlantic present values (magnitude and sign) consistent with those found in previous works on the relationship between Amazon rainfall variations and the SST anomalies in the tropical Pacific and Atlantic. However, austral summer and autumn composites for the years with simultaneous occurrences of El Nino and warm north/south dipole of the SST anomalies in the tropical Atlantic show negative precipitation anomalies extending eastward over the center-eastern Amazon. This result indicates the important role played by the tropical Atlantic in the Amazon anomalous rainfall distribution.

ACRIDICON–CHUVA Campaign: Studying Tropical Deep Convective Clouds and Precipitation over Amazonia Using the New German Research Aircraft HALO

AbstractBetween 1 September and 4 October 2014, a combined airborne and ground-based measurement campaign was conducted to study tropical deep convective clouds over the Brazilian Amazon rain forest. The new German research aircraft, High Altitude and Long Range Research Aircraft (HALO), a modified Gulfstream G550, and extensive ground-based instrumentation were deployed in and near Manaus (State of Amazonas). The campaign was part of the German–Brazilian Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON– CHUVA) venture to quantify aerosol–cloud–precipitation interactions and their thermodynamic, dynamic, and radiative effects by in situ and remote sensing measurements over Amazonia. The ACRIDICON–CHUVA field observations were carried out in cooperation with the second intensive operating period...

The influence of the atmospheric boundary layer on carbon dioxide concentrations over a tropical forest

Abstract Measurements of carbon dioxide concentration and flux have been made over a tropical forest in Brazil. Observations of convective and nocturnal boundary layer height made at the same site have been used to investigate the influence of the atmospheric boundary layer on the concentration measurements. The results explain some of the features of the observed trends in CO 2 concentration and illustrate the importance of taking the atmospheric boundary layer into account when interpreting surface measurements.

The Green Ocean Amazon Experiment (GoAmazon2014/5) Observes Pollution Affecting Gases, Aerosols, Clouds, and Rainfall over the Rain Forest

AbstractThe Observations and Modeling of the Green Ocean Amazon 2014–2015 (GoAmazon2014/5) experiment took place around the urban region of Manaus in central Amazonia across 2 years. The urban pollution plume was used to study the susceptibility of gases, aerosols, clouds, and rainfall to human activities in a tropical environment. Many aspects of air quality, weather, terrestrial ecosystems, and climate work differently in the tropics than in the more thoroughly studied temperate regions of Earth. GoAmazon2014/5, a cooperative project of Brazil, Germany, and the United States, employed an unparalleled suite of measurements at nine ground sites and on board two aircraft to investigate the flow of background air into Manaus, the emissions into the air over the city, and the advection of the pollution downwind of the city. Herein, to visualize this train of processes and its effects, observations aboard a low-flying aircraft are presented. Comparative measurements within and adjacent to the plume followed t...

Analysis of Relative Humidity Sensors at the WMO Radiosonde Intercomparison Experiment in Brazil

Abstract The quality of the vertical distribution measurements of humidity in the atmosphere is very important in meteorology due to the crucial role that water vapor plays in the earth’s energy budget. The radiosonde is the humidity measurement device that provides the best vertical resolution. Also, radiosondes are the operational devices that are used to measure the vertical profile of atmospheric water vapor. The World Meteorological Organization (WMO) has carried out several intercomparison experiments at different climatic zones in order to identify the differences between the available commercial sensors. This article presents the results of an experiment that was carried out in Brazil in 2001 in which major commercial radiosonde manufacturers [e.g., Graw Radiosondes GmbH & Co., KG (Germany); MODEM (France); InterMet Systems (United States); Sippican, Inc. (United States); and Vaisala (Finland)] were involved. One of the main goals of this experiment was to evaluate the performance of the different...

Modificações do microclima e regime hidrológico devido ao desmatamento na Amazônia: estudo de um caso em Rondônia (Ro), Brasil

As mudancas no microclima e no balanco hidrico devido ao desmatamento na Amazonia (regiao de Ji-Parana-RO) foram estudadas com dados meteorologicos coletados de janeiro/92 ate outubro/93, em sitios experimentais de floresta tropical e de pastagem. Observou-se que a troca de vegetacao (desmatamento) reduz a precipitacao total em 10%, diminui a evapotranspiracao real de 24% e tambem apresenta uma maior amplitude termica da temperatura do ar de 1,6 °C. A analise do balanco hidrico mostra claramente que a floresta tropical consegue extrair mais agua do que o sitio de pastagem durante a estacao seca, embora os dois sitios possuam comportamentos similares durante a estacao chuvosa.