Regional Forest-ABL Coupling: Influence on CO2 and Climate
Kenneth J. Davis
Department of Soil, Water, and Climate
University of Minnesota
1991 Upper Buford Circle
St. Paul, MN 55108-6028
phone: +1 612 625 2774
fax: +1 612 625 2208
A. Scott Denning, Colorado State University (numerical modeling)
Dennis D. Baldocchi, U.California, Berkeley (Walker Branch data, micromet)
Jud Isebrands & Ron Teclaw, USDA Forest Service, Rhinelander (field support)
Peter S. Bakwin, NOAA/CMDL (WLEF observations, airborne profiling)
Vince Gutschick, New Mexico State (Chequamegon plant physiology)
Terrestrial Ecosystems and Global Change program (TECO) through DoE.
National Science Foundation via the National Center for Atmospheric Research's Atmospheric Technology Division.
September, 1997 through August, 2000
Radar/RASS measurements of boundary-layer developement will be conducted at two long-term flux tower sites, WLEF in Wisconsin, and Walker Branch in Oak Ridge. The goals are to observe the hypothesized rectifier effect which suggests that boundary-layer CO2 is enhanced over land compared to tropospheric values. If true, this effect has caused significant misinterpretation of the global CO2 distribution. A basic product will be seasonal-scale observations of the diurnal evolution of boundary layer development at each site.
The combination of direct, continuous flux divergence measurements at WLEF with continuous boundary layer depth monitoring provides a unique opportunity to study entrainment processes and plant-soil-cloud-ABL coupling. We will study the coupling between ABL development and net ecosystem exchange (NEE) of CO2. The plant-soil-atmosphere system is dynamically coupled, and these interactions must be observed to understand NEE of CO2. Boundary-layer growth and entrainment are often neglected in this system, but are critical to describing the couple land-atmosphere system. We will work at the WLEF tall-tower (March through October, 1998 and 1999), where flux divergence is observed directly, then attempt a similar study at Walker Branch (February through November, 1999), in an effort to extrapolate these methods to a small tower site, and see if this temperate ecosystem is substantially different from the WLEF region boreal forest. One dimensional coupled land-atmosphere models will complement the observational analyses. The 1998 and 1999 radar/RASS deployments are supported by the National Center for Atmospheric Research's Atmospheric Technology Division.