Energy and water dynamics of a central Amazonian rain forest

Abstract

[1] This paper presents measurements of the energy and water budgets of a tropical rain forest near Manaus, Brazil, in central Amazonia, collected between September 1995 and August 1996. Fluxes of sensible and latent heat were measured using a three-dimensional eddy covariance system mounted above the forest canopy. Using a new approach to analysis of eddy covariance data, we found that the measured fluxes increased significantly when turbulent transport on timescales of 1 to 4 hours was taken into account. With this new analysis, the measured turbulent fluxes almost balanced the incoming net radiation, giving increased confidence in the accuracy of the measured fluxes. Of the 5.56 GJ m À2 yr À1 of solar radiation supplied over the year, 11% were reflected, 15% were lost as net thermal emission, 27% were transported through sensible heat convection, 46% used in evapotranspiration, and 0.5% were used in net carbon fixation. Total annual evapotranspiration was calculated to be 1123 mm, accounting for 54% of total precipitation. Seasonality was an important influence: limited water availability during the dry season caused evapotranspiration to reduce by 50%. Total canopy conductance was linearly correlated to soil moisture content, with typical midday values ranging between 0.8 mol m À2 s À1 in the wet season and 0.3 mol m À2 s À1 in the dry season. Such seasonal behavior is likely to be prevalent in most tropical forest regions, and correct description of dry-season evapotranspiration will require accurate modeling of plant and soil hydraulic properties and knowledge of root distributions.

Cloud characteristics, thermodynamic controls and radiative impacts during the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) experiment

“…Although deep convective clouds have a strong influence on surface shortwave radiation when present, their aggregate impact is limited by a lower frequency of occurrence compared to shallow cumulus. Longwave CRE is typically a factor of 5-6 smaller than SW CRE (e.g., Culf et al, 1998;Malhi et al, 2002;Burleyson et al, 2015). This study will limit most interpretation to SW CRE.…”

Trends in entropy production during ecosystem development in the Amazon Basin

“…net primary productivity; NPP) was assumed to be in steady state and the associated entropy change was not included in our analysis. This was a reasonable assumption, as the energy converted into biomass is only a tiny fraction (less than 1%) of the total energy flux (Malhi et al 2002).…”

An empirical approach to retrieving monthly evapotranspiration over Amazonia

“…Results from the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS; Gash et al 1996) and the more recent Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) (LBA 1996, Avissar et al 2002, Keller et al 2004 have provided a better understanding of the controls of forest E T at seasonal and interannual time scales. These studies have shown not only a higher E T in the dry season than in the wet season but also a higher E T over areas with less rainfall during the dry season in eastern and central Amazonia (Shuttleworth 1988, Nepstad et al 1994, Malhi et al 2002, Sommer et al 2002 well under heavy aerosol and biomass burning conditions, which are frequent in the region (Miura et al 1998). The aim of this work was to develop an empirical approach for the estimation of E T based on the vegetation condition inferred from the EVI and surface net radiation from the International Satellite Cloud Climatology Project (ISCCP; Zhang et al 1995Zhang et al , 2004).…”