HR: 08:00h
AN: A51B-01 INVITED     [PDF]
TI: Regional Carbon Flux Estimation by Inversion of Mesoscale Tracer Transport
AU: * Denning, S
EM: denning@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523-1371
AU: Uliasz, M
EM: marek@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523-1371
AU: Davis, K
EM: davis@essc.psu.edu
AF: Pennsylvania State University, Earth System Science Center, University Park, PA 16802
AU: Richardson, S
EM: srichardson@psu.edu
AF: Pennsylvania State University, Earth System Science Center, University Park, PA 16802
AB: Estimation of carbon fluxes over large regions by tracer transport inversion at global scales is now well established in carbon cycle science, and several studies are now underway in the Europe, the US, and in Brazil to apply similar methods to regional studies over continental areas. Continuous measurements of CO$_2$ have the potential to better constrain regional CO$_2$ fluxes through temporal variations associated with synoptic and mesoscale meteorology, and this class of mesoscale inverse problem is expected to be very important in the upcoming North American Carbon Program. We are conducting a pilot study of mesoscale CO$_2$ inversions using a network of seven continuous analyzers in the region of a tall TV tower (WLEF) in northern Wisconsin. Here we report preliminary results of inverse modeling studies using the new data and experiments using synthetic data for the year 2000. The mesoscale inverse problem is complicated by the need to treat initial conditions, lateral boundary fluxes, and the interaction between mesoscale transport and heterogeneous surface fluxes. Some studies have used zoomed or nested grids in global models to resolve near-field transport, whereas others have specified lateral boundary fluxes from global models. We have taken the latter approach, and simulate tracer transport over a domain much larger than the area of the observations to keep lateral boundaries at a distance. We have simulated the entire year 2000 over a 100 km grid covering most of North America using the CSU Regional Atmospheric Modeling System (RAMS), with two nested grids (dx=20 km and dx=4 km). Meteorological boundary conditions are specified from the NOAA/NCEP reanalysis, with CO$_2$ mixing ratios at lateral boundaries from the mean of the global TransCom models after flux adjustment to match remote flask observations. We simulate the influence of upstream fluxes on hourly measurements of CO$_2$ mixing ratio at each tower using a Lagrangian Particle Dispersion Model that calculates thousands of back trajectories for each observation. Linear combinations of spatial and temporal variations of upstream surface fluxes were then scaled to provide optimum agreement with observations constrained by reasonable diurnal and synoptic variations. Our results highlight the importance of vertical resolution, subgrid-scale turbulence, and cloud-scale transports in determining upstream sources and sinks. Sources within one day's advective travel time of the receptor have a disproportionate influence on the estimated flux, which suggests that spacing of observational networks should be made with this metric in mind. Continuous measurements were found to exert significantly stronger constraint on upstream surface fluxes than subweekly vertical profiles.
UR: http://biocycle.atmos.colostate.edu
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 3307 Boundary layer processes
DE: 3329 Mesoscale meteorology
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting