CD-01 Abstract

Spatial Integration of Regional Carbon Balance in Amazonia

Allan Scott Denning, Colorado State University (US-PI)
Pedro Leite da Silva Dias, IAG/USP (SA-PI)

Under the new Cooperative Agreement, we will perform the following specific tasks in very active collaboration with our colleagues at USP. 

  1. Evaluate the new SiB3 model for a series of Amazon flux sites. This will entail producing or obtaining from collaborators filled micrometeorological timeseries data (no missing values in any “driver” variable) from the three Tapajos sites, and from as many other sites as possible. We will then run multiyear simulations of latent and sensible heat and net ecosystem exchange of CO2 at each site with SiB3 using local site meteorlogy and vegetation parameters. We will compare the simulated and observed seasonality in the three fluxes among sites near Santarem, Manaus, Rondonia, and possibly others. We will investigate the influence of seasonal drought on gross photosynthesis and respiration, and evaluate model simulation of the seasonality of net carbon flux along regional gradients of vegetation and of timing, severity, and duration of the dry season.

  1. Analyze the two-way interaction between drought and physiological stress in Amazonian ecosystems and the implications for possible amplification and persistence of regional drought as simulated in the “Amazon catastrophe” experiment of Cox et al (2000). Coupled simulations with SiB2 in the CSU GCM can reproduce this phenomenon for current climate. We will investigate the cause of this phenomenon in the current model, and explore what must be done in fully coupled climate simulations to produce such a catastrophe, and what model changes are required to avoid it. This work will include local-scale simulations and comparison to drought stress observed in the field, as well as a range of fully coupled experiments with climate models.

  1. Perform a detailed analysis and forward simulation of the Santarém mesoscale campaign of July-August 2001 using SiB3/RAMS5. We will compare simulated to observed meteorology and tower fluxes at the three Tapajos towers. We will focus on the diurnal cycle of sensible and latent heat fluxes and CO2 flux at the three towers, diurnal development of  the planetary boundary layer, its interaction with the regional trade wind circulation, and on mesoscale circulations in the presence of topography and rivers. We will also compare the time-varying vertical structure of CO2 in and just above PBL, and river-land contrasts of mid-morning CO2 on the two days during which we collected these data.

  1. Participate in a major campaign to be organized in the Tapajos region in 2003 or 2004 to investigate the Richey et al hypothesis of major fluxes of CO2 by evasion from inundated lands and open waters. We will provide modeling support using SiB3 and RAMS to simulate “background” fluxes from terre firme forests and pastures, and will also specify evasion fluxes from input obtained from collaborators. Our simulations will be used to interpret airborne and surface-based continuous measurements of CO2 and other tracers. This campaign will be coordinated with members of the Fitzjarrald, Saleska, Ehleringer, Bakwin, Melack, and Richey teams.

  1. Perform regional inversion analyses of data collected by the COBRA-Brazil field campaigns, using SiB3-RAMS and the Lagrangian Particle Dispersion Model developed under the previous Cooperative Agreement. This will be carefully coordinated with other investigators, and is contingent on the approval of the field campaigns in 2003.

  1. Produce improved estimates of monthly Basin-wide carbon balance using a global atmospheric inversion method similar to the TransCom experiments. This will be improved by the inclusion of d13C of CO2 and CO as additional tracers to distinguish among biomass burning, C3 photosynthesis from forests and C4 photosynthesis in pastures and cerrados. The new inversions will also make use of new data collected by airborne sampling (Bakwin/Artaxo team), continuous surface-based measurements of trace gases by the Saleska and Fitzjarrald teams, and isotopic measurements made by the Ehleringer/Ometto team.