HR: 13:40h
AN: B42B-01    [PDF]
TI: Estimates of ABL-scale net carbon dioxide flux in Central Wisconsin
AU: * helliker, b
EM: helliker@catalase.stanford.edu
AF: Carnegie Institution of Washington, Department of Global Ecology, 260 panama st., stanford, ca 94305 United States
AU: Berry, j
EM: joeberry@catalase.stanford.edu
AF: Carnegie Institution of Washington, Department of Global Ecology, 260 panama st., stanford, ca 94305 United States
AU: Betts, A
EM: Akbetts@aol.com
AF: Atmospheric Research, 58 Hendee Lane, Pittsford, vt 05763 United States
AU: Davis, K
EM: davis@essc.psu.edu
AF: Department of Meteorology, Pennsylvania State University, 512 Walker Building, University Park, pa 16802 United States
AU: bakwin, p
EM: Peter.Bakwin@noaa.gov
AF: National Oceanic and Atmospheric Administration- Climate Monitoring and Diagnostics Lab, 325 Broadway R/CMDL1, boulder, co 80305 United States
AB: The atmospheric boundary layer (ABL) is a distinct air mass separated from the free troposphere by a density inversion. The exchanges of sensible heat, water vapor and trace gases which occur at the land surface influence the properties of ABL air. While most studies of the ABL have focused on the dynamics of the diurnal cycle of ABL depth and on changes in trace gas concentration that occur over this time frame, it should be noted that the ABL can persist as a coherent structure over several days. Betts and Ridgeway (1989) and Betts (2000) proposed that the ABL during a sequence of fair weather days can be viewed as a steady-state structure forced on the one hand by surface exchanges and on the other by atmospheric subsidence coupled to the large-scale energy balance of the troposphere. Surface modified air in the ABL is replaced by air descending from areas of subsidence or high pressure, and this flow diverges to areas with storm activity. Given sufficient time, an equilibrium may establish such that the transport of flux by divergent flow balances the surface exchange fluxes. Under these conditions the flux of any trace gas, F$_x$ is, F$_x$ = $-\Delta$ X $\times$ W where $\Delta$ X is the change in mixing ratio of X in the ABL relative to the free troposphere and W is the mean vertical velocity through the top of the ABL. We are specifically interested in using this relationship to calculate net carbon dioxide flux over the area of integration of the ABL from measurements of carbon dioxide mixing ratio made from a tall towers (that sample the ABL) and aircraft measurements (that sample the free troposphere). We describe two independent methods for resolving W at these temporal and spatial scales and show how these estimates, along with measurements of carbon dioxide gradients, can be used to estimate ABL-scale net carbon dioxide flux. Our estimates agree well with eddy-covariance based estimates of regional flux over monthly to annual periods.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 3307 Boundary layer processes
SC: Biogeosciences [B]
MN: 2003 Fall Meeting