Secondary forest as a counterbalance on the deforestation effects: its role on evapotranspiration and water use efficiency.

Published in 19th EGU General Assembly, EGU2017

Scale variability of atmospheric surface layer fluxes of energy and carbon over a tropical rain forest in southwest Amazonia; 1 diurnal conditions

The aim of this study is to investigate the low-frequency characteristics of diurnal turbulent scalar spectra and cospectra near the Amazonian rain forest during the wet and dry seasons. This is because the available turbulent data are often nonstationary and there is no clear spectral gap to separate data into "mean" and "turbulent" parts. Daubechies-8 orthogonal wavelet is used to scale project turbulent signals in order to provide scale variance and covariance estimations. Based on the characteristics of the scale dependence of the scalar fluxes, some classification criteria of this scale dependence are investigated. The total scalar covariance of each 4-hour data run is partitioned in categories of scale covariance contributions. This permits the study of some statistical characteristics of the scalar turbulent fields in each one of these classes and, thus, to give an insight and a possible explanation of the origin of the variability of the scalar fields close to the Amazonian forest. The results have shown that a two-category classification is the most appropriate to describe the kind of observed fluctuations: "turbulent" and "mesoscale" contributions. The largest contribution of the sensible heat, latent heat, and CO2 covariance contributions occurs in the "turbulent" length scales. Mesoscale eddy motions, however, can contribute up to 30% of the total covariances under weak wind conditions. Analysis of scale correlation coefficient [r(Tvq)] between virtual temperature (Tv) and humidity (q) signals shows that the scale patterns of Tv and q variability are not similar and r(Tvq) <1 for all analyzed scales. Scale humidity skewness calculations are negative during the dry season and positive during the wet season. This suggests that different boundary layer moisture regimes occur during the dry and wet seasons

Effect of smoke on the transmissivity of photosynthetically active radiation inside the canopy

International audienceBiomass burning activities emit high concentrations of aerosol particles to the atmosphere. Such particles can interact with solar radiation, decreasing the amount of light reaching the surface and increasing the fraction of diffuse radiation through scattering processes. This work reports results from photosynthetic active radiation (PAR) and aerosol optical depth (AOD) measurements conducted simultaneously at Reserva Biológica do Jaru (Rondonia State, Brazil) during LBA/SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia/ Smoke, Aerosols, Clouds, Rainfall, and Climate) and RaCCI (Radiation, Cloud, and Climate Interactions in the Amazon during the Dry-to-Wet Transition Season) field experiments from 15 September to 15 November 2002. AOD values were retrieved from an AERONET (Aerosol Robotic Network) radiometer, MODIS (Moderate Resolution Spectroradiometer) and a portable sunphotometer from the United States Department of Agriculture-Forest Service. Daily mean downward PAR irradiance at the top of canopy was reduced by up to 50% due to the smoke aerosol particles. This radiation reduction affected turbulent fluxes of sensible and latent heats at the surface, observed particularly for high values of aerosol optical depth. The increase of aerosol optical depth also enhanced the transmission of photosynthetic active radiation inside the canopy. This result was a consequence of enhanced availability of diffuse radiation due to light scattering by the aerosol particles. A complex relationship was identified between light availability inside the canopy and net ecosystem exchange (NEE). The results showed that the increase of aerosol optical depth corresponded to an increase on CO2 exchange, indicating more CO2 uptake by the vegetation. However, for a higher AOD value, the corresponding NEE was lower than for intermediate values. Further studies are needed to better understand these findings, which were reported for the first time for the Amazon region under smoky conditions

Comparative measurements of carbon dioxide fluxes from two nearby towers in a central Amazonian rainforest: the Manaus LBA site

Forests around Manaus have staged the oldest and the longest forest-atmosphere CO2 exchange studies made anywhere in the Amazon. Since July 1999 the exchange of CO2, water, and energy, as well as weather variables, have been measured almost continuously over two forests, 11 km apart, in the Cuieiras reserve near Manaus, Brazil. This paper presents the sites and climatology of the region based upon the new data sets. The landscape consists of plateaus dissected by often waterlogged valleys, and the two sites differ in terms of the relative areas of those two landscape components represented in the tower footprints. The radiation and wind climate was similar to both towers. Generally, both the long-wave and short-wave radiation input was less in the wet than in the dry season. The energy balance closure was imperfect (on average 80%) in both towers, with little variation in energy partitioning between the wet and dry seasons; likely a result of anomalously high rainfall in the 1999 dry season. Fluxes of CO2 also showed little seasonal variation except for a slightly shorter daytime uptake duration and somewhat lower respiratory fluxes in the dry season. The net effect is one of lower daily net ecosystem exchange (NEE) in the dry season. The tower, which has less waterlogged valley areas in its footprint, measured a higher overall CO2 uptake rate. We found that on first sight, NEE is underestimated during calm nights, as was observed in many other tower sites before. However, a closer inspection of the diurnal variation of CO2 storage fluxes and NEE suggests that at least part of the nighttime deficits is recovered from either lateral influx of CO2 from valleys or outgassing of soil storage. Therefore there is a high uncertainty in the magnitude of nocturnal NEE, and consequently preliminary estimates of annual carbon uptake reflecting this range from 1 to 8 T ha-1 y-1, with an even higher upper range for the less waterlogged area. The high uptake rates are clearly unsustainable and call for further investigations into the integral carbon balance of Amazon landscapes

Monitoramento dos fluxos de radiação, energia, CO2 e vapor d'água em superfícies vegetadas.

Aplicações micrometeorológicas; Aspectos metodológicos; Componentes do balanço de radiação e de energia; Fluxos de CO2, vapor d?água e balanço de energia pelo método das Covariâncias dos Vórtices Turbulentos; Características aerodinâmicas e perfil logarítmico do vento; Técnicas de medidas

Amazon deforestation causes strong regional warming

Tropical deforestation impacts the climate through complex land–atmosphere interactions causing local and regional warming. However, whilst the impacts of deforestation on local temperature are well understood, the regional (nonlocal) response is poorly quantified. Here, we used remote-sensed observations of forest loss and dry season land–surface temperature during the period 2001 to 2020 to demonstrate that deforestation of the Amazon caused strong warming at distances up to 100 km away from the forest loss. We apply a machine learning approach to show nonlocal warming due to forest loss at 2–100 km length scales increases the warming due to deforestation by more than a factor 4, from 0.16 K to 0.71 K for each 10-percentage points of forest loss. We estimate that rapid future deforestation under a strong inequality scenario could cause dry season warming of 0.96 K across Mato Grosso state in southern Brazil over the period 2020 to 2050. Reducing deforestation could reduce future warming caused by forest loss to 0.4 K. Our results demonstrate the contribution of tropical deforestation to regional climate warming and the potential for reduced deforestation to deliver regional climate adaptation and resilience with important implications for sustainable management of the Amazon

Effect of smoke and clouds on the transmissivity of photosynthetically active radiation inside the canopy

Biomass burning activities emit high concentrations of aerosol particles to the atmosphere. Such particles can interact with solar radiation, decreasing the amount of light reaching the surface and increasing the fraction of diffuse radiation through scattering processes, and thus has implications for photosynthesis within plant canopies. This work reports results from photosynthetically active radiation (PAR) and aerosol optical depth (AOD) measurements conducted simultaneously at Reserva Biol&#243;gica do Jaru (Rondonia State, Brazil) during LBA/SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia/ Smoke, Aerosols, Clouds, Rainfall, and Climate) and RaCCI (Radiation, Cloud, and Climate Interactions in the Amazon during the Dry-to-Wet Transition Season) field experiments from 15 September to 15 November 2002. AOD values were retrieved from an AERONET (Aerosol Robotic Network) radiometer, MODIS (Moderate Resolution Spectroradiometer) and a portable sunphotometer from the United States Department of Agriculture &ndash; Forest Service. Significant reduction of PAR irradiance at the top of the canopy was observed due to the smoke aerosol particles layer. This radiation reduction affected turbulent fluxes of sensible and latent heats. The increase of AOD also enhanced the transmission of PAR inside the canopy. As a consequence, the availability of diffuse radiation was enhanced due to light scattering by the aerosol particles. A complex relationship was identified between light availability inside the canopy and net ecosystem exchange (NEE). The results showed that the increase of aerosol optical depth corresponded to an increase of CO₂ uptake by the vegetation. However, for even higher AOD values, the corresponding NEE was lower than for intermediate values. As expected, water vapor pressure deficit (VPD), retrieved at 28m height inside the canopy, can also affect photosynthesis. A decrease in NEE was observed as VPD increased. Further studies are needed to better understand these findings, which were reported for the first time for the Amazon region under smoky conditions

Aplicação do modelo de vegetação dinâmica IBIS às condições de floresta de terra firme na região central da Amazônia.

É fundamental para os Modelos de Vegetação Dinâmica Global (DVGM na sigla em inglês) representar corretamente o ciclo diário, as variações sazonais e interanuais das trocas de massa e energia entre o ecossistema e a atmosfera, a hidrologia do solo, a fenologia das plantas e a evolução do estoque de carbono do ecossistema. Este estudo dedica-se a validação e calibração do DVGM IBIS (Integrated Biosphere Simulator) para um ecossistema de floresta tropical úmida de terra firme, localizada na Reserva Biológica do Cuieiras do INPA. Foram utilizados nove anos de dados meteorológicos da torre de fluxo K34, como também dados de diâmetro de árvores, medidas de sonda de nêutrons, de liteira fina e foi realizado um ajuste nos parâmetros físicos do solo do modelo. Os resultados indicam que o modelo representa bem o balanço hídrico, assim como o saldo de radiação e o fluxo de calor latente, porém não representa tão bem os fluxos de calor sensível e de CO2, o índice de área foliar (LAI) e os estoques de liteira fina e biomassa. Os resultados mostram a necessidade de definir um tipo funcional de planta específico para representar a floresta tropical úmida de terra firme da Amazônia e a inclusão de uma subrotina de eventos severos

Methods to Evaluate Land-Atmosphere Exchanges in Amazonia Based on Satellite Imagery and Ground Measurements

During the last three decades, intensive campaigns and experiments have been conducted for acquiring micrometeorological data in the Amazonian ecosystems, which has increased our understanding of the variation, especially seasonally, of the total energy available for the atmospheric heating process by the surface, evapotranspiration and carbon exchanges. However, the measurements obtained by such experiments generally cover small areas and are not representative of the spatial variability of these processes. This chapter aims to discuss several algorithms developed to estimate surface energy and carbon fluxes combining satellite data and micrometeorological observations, highlighting the potentialities and limitations of such models for applications in the Amazon region. We show that the use of these models presents an important role in understanding the spatial and temporal patterns of biophysical surface parameters in a region where most of the information is local. Data generated may be used as inputs in earth system surface models allowing the evaluation of the impact, both in regional as well as global scales, caused by land-use and land-cover changes