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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Emission of NO and deposition of O3 in a tropical forest system

Rates for emission of NO and deposition of O3 were measured at a tropical forest site in Reserve Adolfo Ducke, near Manaus, Brazil. Two independent techniques were used to determine the NO flux: (1) a soil enclosure method and (2) a method based on simultaneous observations of NO and O3 vertical profiles at night, when NO is irreversibly removed by reaction with O3. Results obtained using the two techniques agreed well, giving an average NO flux of 5.2 + or - 1.7 x 10 to the 10th molecules/sq cm per sec and an average vertical exchange coefficient of 2.2 x 10 to the 3rd cu cm/sec. Sources of NO from tropical forest soils may be important for global atmospheric chemistry. Rapid removal of O3 was observed in the lowest levels of the forest. The nocturnal deposition rate was estimated to be 5.6 + or - 2.5 x 10 to the 11th molecules/sq cm per sec through the 6-m level. The large deposition rate for O3 is consistent with the strong sink inferred from observations of ozone in the Amazon region.

Kaplan, W. A.↗
NASA NTRS2019

Widespread Increase of Boreal Summer Dry Season Length Over the Congo Rainforest

Dry season length strongly influences tropical rainforest vegetation and is largely determined by precipitation patterns. Over the Amazon, the dry season length has increased since 1979 and severe short-term droughts have occurred. However, similar changes have not been investigated for the world’s second largest rainforest, the Congo Basin, where long-term drying and large-scale declines in forest greenness and canopy water content were reported. Here we present observational evidence for widespread increases in the boreal summer (June–August) dry season length over the Congo Basin since the 1980s, from both hydrological and ecological perspectives. We analyzed both dry season onset and dry season end via multiple independent precipitation and satellite derived vegetation datasets for the period 1979–2015. The dry season length increased by 6.4–10.4 days per decade in the period 1988–2013, primarily attributed to an earlier dry season onset and a delayed dry season end. The earlier dry season onset was caused by long-term droughts due to decreased rainfall in the pre-dry season (April–June). The delayed dry season end resulted from insufficiently replenished soil moisture, which postpones the start of the next wet season and hinders vegetation regrowth. If such changes continue, the enhanced water stress in a warming climate may affect the carbon cycle and alter the composition and structure of evergreen rainforest.

Congo rainforest growing season NDVI SIF↗
NASA NTRS1990

The Amazon Boundary-Layer Experiment (ABLE 2B) - A meteorological perspective

The Amazon Boundary-Layer Experiments (ABLE) 2A and 2B, which were performed near Manaus, Brazil in July-August, 1985, and April-May, 1987 are discussed. The experiments were performed to study the sources, sinks, concentrations, and transports of trace gases and aerosols in rain forest soils, wetlands, and vegetation. Consideration is given the design and preliminary results of the experiment, focusing on the relationships between meteorological scales of motion and the flux, transports, and reactions of chemical species and aerosols embedded in the atmospheric fluid. Meteorological results are presented and the role of the meteorological results in the atmospheric chemistry experiment is examined.

Garstang, Michael↗
NASA NTRS1992

Strategies for detection of floodplain inundation with multi-frequency polarimetric SAR

Mapping of floodplain inundation patterns is a key element in developing hydrological and biogeochemical models for large tropical river basins such as the Amazon. Knowledge of the time sequence of inundation is necessary to determine both water routing and biogenic gas fluxes. Synthetic Aperture Radar (SAR) is uniquely suited for this application because of its ability to penetrate cloud cover and, in many cases, to detect flooding beneath a forest or herbaceous canopy. A procedure for discriminating flooded forest, flooded herbaceous vegetation, and open water from other cover types for a coastal wetland site on the lower Altamaha floodplain, Georgia, emphasizing robust classifiers that are not site-specific is currently being developed.

Hess, Laura L.↗
NASA NTRS1990

Methane flux from the Amazon River floodplain - Emissions during rising water

Methane flux data obtained during a period of high and falling water level in the course of the dry season of 1985 (the Amazon Boundary Layer Experiment, ABLE 2A) and a period of moderate and rising water during the wet season of 1987 (ABLE 2B) were used to characterize the influence of seasonal variations in the vegetation, water column depth, and chemistry, as well as atmospheric dynamics, on the methane flux from the Amazon River floodplain. It was found that the annual estimate of methane from wetlands is identical to the annual estimate made by Matthews and Fung (1987) (both at 111 Tg). However, it was found that peatlands between 50 and 70 N contribute 39 Tg, with the large areas of forested and nonforested bogs making up 37 Tg of this figure, while the figures of Matthews and Fung were 63 and 62 Tg, respectively.

Bartlett, Karen B.↗
DOE OSTI2025

AmeriFlux BR-Ji3 Ji-Paraná/RO - Reserva Biológica do Jaru (RBJ)

This is the AmeriFlux version of the carbon flux data for the site BR-Ji3 Ji-Paraná/RO - Reserva Biológica do Jaru (RBJ). Site Description - The BR-Ji3, RBJ tower (LBA Network) is deployed in a primary forest in the Reserva Biologica do Jaru, management to ICMBio, at 130 km of Ji-Paraná city, in the road to Vale do Paraíso.

Araujo, Alessandro [Brazilian Agricultural Researc↗
DOE OSTI2026

AmeriFlux FLUXNET-1F BR-Ji3 Ji-Paraná/RO - Reserva Biológica do Jaru (RBJ)

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site BR-Ji3 Ji-Paraná/RO - Reserva Biológica do Jaru (RBJ). This is the FLUXNET version of the carbon flux data for the site BR-Ji3 Ji-Paraná/RO - Reserva Biológica do Jaru (RBJ) produced by applying the standard ONEFlux (1F) software. Site Description - The BR-Ji3, RBJ tower (LBA Network) is deployed in a primary forest in the Reserva Biologica do Jaru, management to ICMBio, at 130 km of Ji-Paraná city, in the road to Vale do Paraíso.

Araujo, Alessandro [Brazilian Agricultural Researc↗
NASA NTRS1984

The Amazon and climate

The climatologies of cloudiness and precipitation for the Amazon are reviewed. The physical causes of observed features are explained. The question whether deforestation leads to a reduction in evapotranspiration into the atmosphere is examined, as well as the reduction in precipitation and its implication for the global climate. There are indications that for large scale clearing of tropical rain forests there would indeed be a reduction in rainfall, which would have global effects in terms of climate and weather.

Nobre, C. A.↗
NASA NTRS2017

A Pan-Tropical Cascade of Fire Driven by El Nino/Southern Oscillation

The El Nino/Southern Oscillation (ENSO) has a pronounced influence on year-to-year variations in climate. The response of fires to this forcing is complex and has not been evaluated systematically across different continents. Here we use satellite data to create a climatology of burned-area and fire emissions responses, drawing on six El Nino and six La Nina events during 1997-2016. On average, reductions in precipitation and terrestrial water storage increased fire emissions in pan-tropical forests by 133% during and following El Nino as compared with La Nina. Fires peaked in equatorial Asia early in the ENSO cycle when El Nino was strengthening (Aug-Oct), before moving to southeast Asia and northern South America (Jan-Apr), Central America (Mar-May) and the southern Amazon (Jul-Oct) during the following year. Large decreases in fire occurred across northern Australia during Sep-Oct of the second year from a reduced fuel availability. Satellite observations of aerosols and carbon monoxide provided independent confirmation of the spatiotemporal evolution of fire anomalies. The predictable cascade of fire across different tropical continents described here highlights an important time delay in the Earth system's response to precipitation redistribution. These observations help to explain why the growth rate of atmospheric CO2 increases during El Nino and may contribute to improved seasonal fire forecasts.

Chen, Yang↗
NASA NTRS2002

The Effects of Amazon Deforestation on Rainfall

This study begins with the hypothesis that heavily deforested regions will experience increased surface heating, leading to local circulations that will ultimately enhance the rainfall, or at least, change the pattern of diurnal evolution of rainfall. This would be an important finding because several modeling studies have concluded that widespread deforestation would lead to decreased rainfall. Towards that end rain estimates from a combined GOES infrared/TRMM microwave technique were analyzed with respect to percent forest cover from Landsat data (courtesy of TRFIC at Michigan State University) and GOES visible channel data over a deforested area in Rondonia (southwest Brazil). Five 1" x 1" areas of varying forest cover were examined during the onset of the wet season in Amazonia (Aug-Sept), when the effects of the surface would not be dominated by large-scale synoptic weather patterns. Preliminary results revealed that: maximum rainfall fell in most deforested area; heavily forested areas received the least rainfall; cumulus cloud development initiated at borders; the amplitude of the diurnal cycle of precipitation was a function of th surface cover. Further work will be presented detailing effects of land surface cover on the GOES infrared-measured surface heating, GOES visible observed cumulus development, thunderstorm initiation based on the location of temperature minima in the infrared data, and estimated rainfall and its diurnal cycle from a combined GOES/TRMM technique. Rainfall estimates derived from non-geosynchronous microwave observations (i.e. Goddard Profiling Algorithm, GPROF) will also be examined.

Starr, David OC.↗
NASA NTRS1991

Global biomass burning - Atmospheric, climatic, and biospheric implications

The present volume discusses the biomass burning (BMB) studies of the International Global Atmospheric Chemistry project, GEO satellite estimation of Amazonian BMB, remote sensing of BMB in West Africa with NOAA-AVHRR, an orbital view of the great Chinese fire of 1987, BMB's role in tropical rainforest reduction, CO and O3 measurements of BMB in the Amazon, effects of vegetation burning on the atmospheric chemistry of the Venezuelan savanna, an assessment of annually-burned biomass in Africa, and light hydrocarbon emissions from African savanna burnings. Also discussed are BMB in India, trace gas and particulate emissions from BMB in temperate ecosystems, ammonia and nitric acid emissions from wetlands and boreal forest fires, combustion emissions and satellite imagery of BMB, BMB in the perspective of the global carbon cycle, modeling trace-gas emissions from BMB, NO(x) emissions from BMB, and cloud-condensation nuclei from BMB.

Levine, Joel S.↗
NASA NTRS1990

The atmospheric sulfur cycle over the Amazon Basin. II - Wet season

The fluxes and concentrations of atmospheric sulfur species were determined at ground level and from aircraft over the Amazon Basin during the 1987 wet season, providing a comprehensive description of the sulfur cycle over a remote tropical region. The vertical profile of dimethylsulfide (DMS) during the wet season was found to be very similar to that measured during the dry season, suggesting little seasonal variation in DMS fluxes. The concentrations of H2S were almost an order of magnitude higher than those of DMS, which makes H2S the most important biogenic source species in the atmosheric sulfur cycle over the Amazon Basin. Using the gradient-flux approach, the flux of DMS at the top of the tree canopy was estimated. The canopy was a source of DMS during the day, and a weak sink during the night. Measurements of sulfur gas emissions from soils, using the chamber method, showed very small fluxes, consistent with the hypothesis that the forest canopy is the major source of sulfur gases. The observed soil and canopy emission fluxes are similar to those measured in temperate regions. The concentrations of SO2 and sulfate aerosol in the wet season atmosphere were similar to dry season values.

Andreae, M. O.↗
NASA NTRS1997

Land-Use Change, Soil Process and Trace Gas Fluxes in the Brazilian Amazon Basin

We measured changes in key soil processes and the fluxes of CO2, CH4 and N2O associated with the conversion of tropical rainforest to pasture in Rondonia, a state in the southwest Amazon that has experienced rapid deforestation, primarily for cattle ranching, since the late 1970s. These measurements provide a comprehensive quantitative picture of the nature of surface soil element stocks, C and nutrient dynamics, and trace gas fluxes between soils and the atmosphere during the entire sequence of land-use change from the initial cutting and burning of native forest, through planting and establishment of pasture grass and ending with very old continuously-pastured land. All of our work is done in cooperation with Brazilian scientists at the Centro de Energia Nuclear na Agricultura (CENA) through an extant official bi-lateral agreement between the Marine Biological Laboratory and the University of Sao Paulo, CENA's parent institution.

Melillo, Jerry M.↗
NASA NTRS1987

Atmospheric surface and boundary layers of the Amazon Basin

Three phases of work were performed: design of and preparation for the Amazon Boundary Layer Experiment (ABLE 2-A); execution of the ABLE 2-A field program; and analysis of the ABLE 2-A data. Three areas of experiment design were dealt with: surface based meteorological measurements; aircraft missions; and project meteorological support. The primary goal was to obtain a good description of the structure of the atmosphere immediately above the rain forest canopy (top of canopy to a few thousand meters), to describe this region during the growing daytime phase of the boundary layer; and to examine the nighttime stratified state. A secondary objective was to examine the role that deep convective storms play in the vertical transport of heat, water vapor, and other trace gases. While significant progress was made, much of the analysis remains to be done.

Garstang, Michael↗
NASA NTRSDate not supplied

An Analysis of Fire Dynamics Inside and Outside Indigenous Territories and Protected Areas in a Brazilian Agricultural Frontier

Sustainable land management, including protected areas, is integral to conserving tropical ecosystems and reducing carbon emissions in the Brazilian Amazon. In disturbed Amazon landscapes fire is commonly used to clear land or old fields for agriculture or pastureland. Human-set fires are the most common driver of deforestation and carbon emissions in Amazonia. Evidence suggests that indigenous groups have also used fire for land management since Pre-Columbian times. However, when used unsustainably, fires in this biome can result in degradation of forest ecosystems, decreased ability to store carbon, and health impacts resulting from smoke and particulate matter. Due to the uptick in fire occurrences in 2019, more restrictions on fire use were implemented in 2019 and 2020. Presidential decrees 9.992/2019 and 10.424/2020 banned fire use completely for periods of 60 and 120 days respectively, except by indigenous communities or authorities. Despite these bans, fire use remained high in both years. In the state of Mato Grosso, agricultural activity and expansion influences the anthropogenic fire regime. Indigenous and protected areas cover approximately 25% of its land area.

remote sensing↗
DOE OSTI2022

The Influence of Shallow Cloud Populations on Transitions to Deep Convection in the Amazon

Abstract In this study, a pair of convection-permitting (2-km grid spacing), month-long, wet-season Weather Research and Forecasting (WRF) Model simulations with and without the eddy-diffusivity mass-flux (EDMF) scheme are performed for a portion of the Green Ocean Amazon (GoAmazon) 2014/15 field campaign period. EDMF produces an ensemble of subgrid-scale convective plumes that evolve in response to the boundary layer meteorological conditions and can develop into shallow clouds. The objective of this study is to determine how different treatments of shallow cumulus clouds (i.e., with and without EDMF) impact the total cloud population and precipitation across the Amazonian rain forest, with emphasis on impacts on the likelihood of shallow-to-deep convection transitions. Results indicate that the large-scale synoptic conditions in the EDMF and control simulations are nearly identical; however, on the local scale their rainfall patterns diverge drastically and the biases decrease in EDMF. The EDMF scheme significantly increases the frequency of shallow clouds, but the frequencies of deep clouds are similar between the simulations. Deep convective clouds are tracked using a cloud-tracking algorithm to examine the impact of shallow cumulus on the surrounding ambient environment where deep convective clouds initiate. Results suggest that a rapid increase of low-level cloudiness acts to cool and moisten the low to midtroposphere during the day, favoring the transition to deep convection.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Storms Are an Important Driver of Change in Tropical Forests

Tropical forest dynamics and composition have changed over recent decades, but the proximate drivers of these changes remain unclear. Investigations into these trends have focused on increasing drought stress, CO 2 , temperature, and fires, whereas convective storms are generally overlooked. We argue that existing literature provides clear support for the importance of storms as drivers of forest change. We reanalyze the largest plot-based study of tropical forest carbon dynamics to show that lightning frequency—an indicator of storm activity—strongly predicts forest carbon storage and residence time, and its inclusion improves model fit and weakens evidence for the effects of high temperatures. Convective storm activity has increased 5%–25% per decade over the past half century. Extrapolating from historic trends, we estimate that storms likely contribute ca. 50% of the reported increases in biomass mortality across Amazonia, with all realistic combinations of assumptions indicating a possible range of 12%–118%. Spatial variation in storm activity shows weak relationships with drought, demonstrating that forests can experience high drought stress, high storm activity, or both. Accordingly, we hypothesise that convective storms are among the most important drivers of tropical forest change, and as such, they require significant research investment to avoid misguiding science, policy, and management.

biomass carbon↗
DOE OSTI2025

Seasonal investigation of ultrafine-particle organic composition in an eastern Amazonian rainforest

Abstract. Reports on the composition of ultrafine particles (<100 nm in diameter) in the Amazon are scarce, due in part to the fact that new-particle formation has rarely been observed near ground level. Ultrafine particles near the surface have nevertheless been observed, leaving open questions regarding the sources and chemistry of their formation and growth, particularly as these vary across seasons. Here, we present measurements of the composition of ultrafine particles collected in the Tapajós National Forest (2.857° S, 54.959° W) during three different seasonal periods: 10–30 September 2016 (SEP), 18 November–23 December 2016 (DEC), and 22 May–21 June 2017 (JUN). Size-selected (5–70 nm) particles were collected daily (for 22 h each day) using an offline sampler. Samples collected during the three time periods were compiled and analyzed using liquid chromatography coupled with Orbitrap high-resolution mass spectrometry. Our findings suggest a sustained influence of isoprene organosulfate chemistry on ultrafine particles from the different periods. We present chemical evidence that indicates that biological-spore fragmentation impacted ultrafine-particle composition during the late wet season (JUN), while chemical markers for biomass burning and secondary chemistry peaked during the dry season (SEP and DEC). Higher oxidation states and degrees of unsaturation were observed for organics in the dry season (SEP and DEC), suggesting greater extents of aerosol aging. Finally, applying a volatility parameterization to the observed compounds suggests that organic sulfur species are likely key drivers of new-particle growth in the region due to their low volatility compared to other species.

54 ENVIRONMENTAL SCIENCES↗