How well can regional fluxes be derived from smaller-scale estimates?

Regional surface fluxes are essential lower boundary conditions for large scale numerical weather and climate models and are the elements of global budgets of important trace gases. Surface properties affecting the exchange of heat, moisture, momentum and trace gases vary with length scales from one meter to hundreds of km. A classical difficulty is that fluxes have been measured directly only at points or along lines. The process of scaling up observations limited in space and/or time to represent larger areas was done by assigning properties to surface classes and combining estimated or calculated fluxes using an area weighted average. It is not clear that a simple area weighted average is sufficient to produce the large scale from the small scale, chiefly due to the effect of internal boundary layers, nor is it known how important the uncertainty is to large scale model outcomes. Simultaneous aircraft and tower data obtained in the relatively simple terrain of the western Alaska tundra were used to determine the extent to which surface type variation can be related to fluxes of heat, moisture, and other properties. Surface type was classified as lake or land with aircraft borne infrared thermometer, and flight level heat and moisture fluxes were related to surface type. The magnitude and variety of sampling errors inherent in eddy correlation flux estimation place limits on how well any flux can be known even in simple geometries

Evaluating the Contribution of Climate Forcing and Forest Dynamics to Accelerating Carbon Sequestration by Forest Ecosystems in the Northeastern U.S.

We used 10 Hz eddy flux signals and 0.2 Hz incident radiation (global shortwave and PAR) records from Harvard Forest (Massachusetts) and Tapajos National Forest (Brazil) to establish empirical relationships among directly measured cloud type and cover percentage and corresponding PAR fluctuations and its diffuse fraction. In future work such a cloud characterization will be related to water and light use efficiency estimates for each of these ecosystems. We developed empirical relationships to link sky cover type and fraction (measured with the ceilometer) to incident direct and diffuse PAR. We developed a methodology for constructing synthetic incident solar radiation time series based on operational reports of sky cover and cloud type from National Weather Service METAR reports. The aim of this work is to document the temporal and spectral properties radiation incident on the canopy, as a first step toward developing a sky-type parameterization for the net carbon uptake models

Quantifying advective and nonstationary effects on eddy fluxes in the AmeriFlux network

Our goal was to study the flows within and above of a forested area and assess the degree to which horizontal subcanopy motions transport significant amounts of CO2. This process can explain why ecosystem respiration appears to be underestimated on calm nights. It is essential to understand the physical and biological mechanisms that determine relevant processes that occur on these âÃÂÃÂsuspectâÃÂànights

Near Surface Turbulence Occurring over Heterogeneous Terrain and Stable Conditions

Fluxos médios de um conjunto de estações localizadas em uma região de superfície heterogênea, são dispostos em função de um número de Richardson regional (Ribr). O procedimento de se manter turbulência, mesmo quando Ribr se encontra acima de seu valor critico (Ricr), usado em modelos numéricos de previsão do tempo, é justificado experimentalmente. Os resultados experimentais mostram que a turbulência não cessa mesmo quando Ribr >> Ricr. A rede de estações mostra que existem locais preferências para as transferências de momentum e calor para uma região com superfície heterogênea sob mesmas condições de estabilidade regional

Characterization of Interannual and Seasonal Patterns and Extremes in 41 Years of Precipitation data from Belterra, Pará, Brazil

Este trabalho identificou padrões interanuais e sazonais, e meses com valores extremos de precipitação total num conjunto de dados de precipitação mensal de 41 anos da Belterra, no oeste do Estado do Pará, Brasil. Apesar de intensas mudanças no uso da terra nos últimos anos e a variabilidade natural da precipitação na região, nenhuma tendência foi descrita para precipitação total anual, sazonal ou eventos extremos

Understanding water and energy fluxes in the Amazonia: Lessons from an observation-model intercomparison

Tropical forests are an important part of global water and energy cycles, but the mechanisms that drive seasonality of their land-atmosphere exchanges have proven challenging to capture in models. Here, we (1) report the seasonality of fluxes of latent heat (LE), sensible heat (H), and outgoing short and longwave radiation at four diverse tropical forest sites across Amazonia—along the equator from the Caxiuanã and Tapajós National Forests in the eastern Amazon to a forest near Manaus, and from the equatorial zone to the southern forest in Reserva Jaru; (2) investigate how vegetation and climate influence these fluxes; and (3) evaluate land surface model performance by comparing simulations to observations. We found that previously identified failure of models to capture observed dry-season increases in evapotranspiration (ET) was associated with model overestimations of (1) magnitude and seasonality of Bowen ratios (relative to aseasonal observations in which sensible was only 20%–30% of the latent heat flux) indicating model exaggerated water limitation, (2) canopy emissivity and reflectance (albedo was only 10%–15% of incoming solar radiation, compared to 0.15%–0.22% simulated), and (3) vegetation temperatures (due to underestimation of dry-season ET and associated cooling). These partially compensating model-observation discrepancies (e.g., higher temperatures expected from excess Bowen ratios were partially ameliorated by brighter leaves and more interception/evaporation) significantly biased seasonal model estimates of net radiation (Rn), the key driver of water and energy fluxes (LE ~ 0.6 Rn and H ~ 0.15 Rn), though these biases varied among sites and models. A better representation of energy-related parameters associated with dynamic phenology (e.g., leaf optical properties, canopy interception, and skin temperature) could improve simulations and benchmarking of current vegetation–atmosphere exchange and reduce uncertainty of regional and global biogeochemical models

SECA E A SAÚDE DAS POPULAÇÕES RESIDENTES EM REGIÕES DA AMAZÔNIA BRASILEIRA NOS ANOS DE 2005, 2010 E 2015

O objetivo deste trabalho é verificar os impactos ocasionados pelos três últimos eventos de seca na saúde da população de catorze municípios na Amazônia, agrupados em quatro grupos com características pluviométricas homogêneas. Utilizaram-se dados diários e mensais de precipitação e temperatura do ar disponibilizado pelo Banco de Dados Meteorológicos para Ensino e Pesquisa do Instituto Nacional de Meteorologia e de internações por doenças respiratórias do Sistema Único de Saúde, DATASUS, do período de 2000 a 2015. Levando-se em consideração as especificidades dos dados em estudo utilizou-se a modelagem via Equações de Estimação Generalizada para captar associações significativas e o risco relativo de aumento da ocorrência das internações da população exposta a ausência de chuva. Os resultados mostraram que as estações que muito sofreram com a seca de 2005 (região A) localizada a sudoeste da Amazônia também foram pouco afetadas negativamente pelo evento de 2015. Embora o evento de seca de 2010 tenha sido mais extenso espacialmente do que 2005, o efeito da diminuição das chuvas a partir dos dados observados de um evento pra outro só se mostrou perceptível nas estações da região B, mais ao centro da Amazônia. Já a seca de 2015 teve maior impacto nas estações das regiões C e D. As populações consideradas mais vulneráveis por meio dos riscos captados pelo modelo foram Itaituba (região C), Monte Alegre e Porto de Moz (região D). Conclui-se que ao comparar as regiões percebe-se que os três eventos de seca afetam de forma diferente os quatros grupos, o que provavelmente está associado ao efeito diferencial dos mecanismos causadores das secas nas diferentes áreas da Amazônia.

Agriculture and forest: A sustainable strategy in the Brazilian Amazon

Abstract Large-scale agriculture is increasing in anthropogenically modified areas in the Amazon Basin. Crops such as soybean, maize, oil palm, and others are being introduced to supply the world demand for food and energy. However, the current challenge is to enhance the sustainability of these areas by increasing efficiency of production chains and to improve environmental services. The Amazon Basin has experienced a paradigm shift away from the traditional slash-and-burn agricultural practices, which offers decision makers the opportunity to make innovative interventions to enhance the productivity in previously degraded areas by using trees to ecological advantage. This study describes a successful experiment integrating the production of soybean and paricá (Glycine max L. and Schizolobium amazonicum) based on previous research that indicated potential topoclimatic zones for planting paricá in the Brazilian state of Pará. This paper shows that a no-tillage system reduces the effects of drought compared to conventional tillage still used by many farmers in the region. The integrated system was implemented during the 2014/2015 season in 234.6 ha in the high-potential zone in the municipality of Ulianópolis, Pará. Both soybean and paricá were planted simultaneously. Paricá was planted in 5 m x 2 m inter-tree spacing totaling 228x10 3 trees per hectare and soybean, in 4 m x 100 m spacing, distributed in nine rows with a 0.45 m inter-row distance, occupying 80% of the area. The harvested soybean production was 3.4 t ha -1 , higher than other soybean monocultures in eastern Pará. Paricá benefited from soybean fertilization in the first year: It exhibited rapid development in height (3.26 m) and average diameter (3.85 cm). Trees and crop rotation over the following years is six years for forest species and one year for each crop. Our results confirm there are alternatives to the current production systems able to diminish negative impacts resulting from monoculture. In addition, the system provided environmental services such as reduced soil erosion and increased carbon stock by soil cover with no-tillage soybean cultivation. The soybean cover contributes to increased paricá thermal regulation and lower forestry costs. We concluded that innovative interventions are important to show local farmers that it is possible to adapt an agroforest system to large-scale production, thus changing the Amazon