Airborne observations reveal elevational gradient in tropical forest isoprene emissions.

Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants and aerosols. Isoprene emission rates vary over several orders of magnitude for different plants, and characterizing this immense biological chemodiversity is a challenge for estimating isoprene emission from tropical forests. Here we present the isoprene emission estimates from aircraft eddy covariance measurements over the Amazonian forest. We report isoprene emission rates that are three times higher than satellite top-down estimates and 35% higher than model predictions. The results reveal strong correlations between observed isoprene emission rates and terrain elevations, which are confirmed by similar correlations between satellite-derived isoprene emissions and terrain elevations. We propose that the elevational gradient in the Amazonian forest isoprene emission capacity is determined by plant species distributions and can substantially explain isoprene emission variability in tropical forests, and use a model to demonstrate the resulting impacts on regional air quality.

Concentração e fluxo de CO2 sobre o reservatório hidrelétrico de Balbina (AM) / CO2 concentration and flux in hydroelectric reservoir of Balbina (AM)

RESUMO O reservatório de Balbina (59º 28’ 50’’ W, 1º 53’ 25’’ S), localizado próximo à cidade de Manaus, Amazonas, na Amazônia Central, é o segundo maior reservatório hidrelétrico em área localizado na Bacia Amazônica. Nesse reservatório foram realizadas medições de CO2 em alta frequência (10 Hz), do fluxo de CO2, com analisador de gás por infravermelho (IRGA) acoplado a uma câmara flutuante, e de variáveis meteorológicas, com uma boia instrumentada a 2 m da superfície do lago. A concentração média de CO2 foi de 392 e 426 ppm para o dia e a noite, respectivamente, e a taxa de emissão média diária, de 40.427±24.040 µmol.m-­2.d-1. A acumulação da concentração de CO2 sobre o lago à noite, além da respiração, mostra ter sido afetada por baixas velocidades do vento e convecção do lado da água, processos físicos que trazem altas concentrações de CO2 para a superfície e a presença de brisa terrestre. Os fluxos não apresentaram diferenças estatisticamente significantes com as variáveis meteorológicas e foram consideravelmente mais baixos do que os encontrados em um estudo anterior para o mesmo lago. No entanto, os valores concordam com os encontrados em outros estudos em lagos tropicais amazônicos e outros reservatórios.

ABSTRACT 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.

Hydroclimatic variables associated with El Nino and La Nina events at the Curuá-Una hydroelectric reservoir, Central Amazonia / 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.

As anomalias da temperatura da superfície do mar (TSM) influenciam as chuvas e consequentemente o regime de subida e descida do nível dos rios na região amazônica. O objetivo deste estudo foi verificar a influência de eventos El Niño Oscilação Sul (ENSO) sobre algumas variáveis hidroclimáticas e identificar a existência de tendência sobre essas variáveis para o reservatório de Curuá-Una no oeste do Pará. Utilizaram-se 27 anos de dados mensais de precipitação e vazão para identificar possíveis tendências utilizando um teste não paramétrico (Mann Kendall, p<0.05) e calculado o índice de precipitação normalizado (SPI). Os resultados apresentam tendência positiva da influência do ENOS sobre as variáveis hidroclimáticas, embora não foi observado um aumento na precipitação para o período de 1977 a 2004. O índice de precipitação normalizado revela que os eventos extremos de seca e precipitação estão relacionados com eventos de El Niño e La Niña e que os eventos de baixa precipitação foram mais intensos nas décadas de 80 e 90. Os resultados revelam ainda que eventos de El Niño afetam diretamente o balanço hídrico da micro bacia do reservatório de Curuá-Una, como recentemente em 2015.

Amazon rainforest exchange of carbon and subcanopy air flow: Manaus LBA site--a complex terrain condition.

On the moderately complex terrain covered by dense tropical Amazon Rainforest (Reserva Biologica do Cuieiras--ZF2--02°36'17.1'' S, 60°12'24.4'' W), subcanopy horizontal and vertical gradients of the air temperature, CO(2) concentration and wind field were measured for the dry and wet periods in 2006. We tested the hypothesis that horizontal drainage flow over this study area is significant and can affect the interpretation of the high carbon uptake rates reported by previous works at this site. A similar experimental design as the one by Tóta et al. (2008) was used with a network of wind, air temperature, and CO(2) sensors above and below the forest canopy. A persistent and systematic subcanopy nighttime upslope (positive buoyancy) and daytime downslope (negative buoyancy) flow pattern on a moderately inclined slope (12%) was observed. The microcirculations observed above the canopy (38 m) over the sloping area during nighttime presents a downward motion indicating vertical convergence and correspondent horizontal divergence toward the valley area. During the daytime an inverse pattern was observed. The micro-circulations above the canopy were driven mainly by buoyancy balancing the pressure gradient forces. In the subcanopy space the microcirculations were also driven by the same physical mechanisms but probably with the stress forcing contribution. The results also indicated that the horizontal and vertical scalar gradients (e.g., CO(2)) were modulated by these micro-circulations above and below the canopy, suggesting that estimates of advection using previous experimental approaches are not appropriate due to the tridimensional nature of the vertical and horizontal transport locally. This work also indicates that carbon budget from tower-based measurement is not enough to close the system, and one needs to include horizontal and vertical advection transport of CO(2) into those estimates.

On the influences of the El Niño, La niña and Atlantic Dipole Paterni 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 Niño or La Niña) 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 Niño or La Niña) 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 Niño 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.

A influência dos modos dc variabilidade climática dc grande escala dominantes no Pacifico e Atlântico nas chuvas da Amazônia é investigada. A técnica de compósitos das anomalias dc precipitação na Amazônia é usada neste trabalho. Os anos base destes compósitos são aqueles do período 1960-1998 com ocorrências de extremos na Oscilação Sul (El Niño ou La Niña) e de padrão de dipolo norte/sul quente (ou frio) nas anomalias de TSM no Atlântico tropical. Dipolo quente (frio) significa anomalias positivas (negativas) no Atlântico tropical Norte e negativas (positivas) no Atlântico tropical Sul. Compósitos dc verão e outono austrais para extremos na Oscilação Sul (El Niño ou La Niña) e independente para padrão de dipolo norte/sul (quente ou frio) de anomalias de TSM no Atlântico tropical, apresentam valores (magnitude e signal) consistentes com aqueles encontrados cm trabalhos anteriores sobre a relação entre as variações de precipitação na Amazônia c anomalias de TSM no Pacífico e Atlântico tropicais. No entanto, compósitos dos verões e outonos austrais para os anos com ocorrências simultâneas de El Niño e dipolo quente norte/sul dc anomalias de TSM no Atlântico tropical mostram anomalias negativas de precipitação estendendo-se para leste sobre a Amazônia ccntro-leste. Este resultado indica o importante papel desempenhado pelo Atlântico tropical na distribuição anômala de precipitação na Amazônia.