HR: 16:45h
AN: B34A-03    [Abstracts]
TI: Simulating Energy, Water and Carbon Fluxes at the Shortgrass Steppe Long Term Ecological Research (LTER) Site
AU: * Beltran-Przekurat, A B
EM: abeltran@atmos.colostate.edu
AF: Colorado State University, 1371 Campus Delivery Atmospheric Science Department, Fort Collins, CO 80523 United States
AU: Pielke, R A
EM: pielke@atmos.colostate.edu
AF: Colorado State University, 1371 Campus Delivery Atmospheric Science Department, Fort Collins, CO 80523 United States
AU: Morgan, J A
EM: jack.morgan@ars.usda.gov
AF: USDA-ARS Rangeland Resources Research Unit, Crops Research Lab., 1701 Center Ave., Fort Collins, CO 80526 United States
AU: Burke, I C
EM: indy@cnr.colostate.edu
AF: Colorado State University, Department of Forest, Range, and Watershed Stewardship, Fort Collins, CO 80523 United States
AB: Coupled atmospheric-biospheric models are a particularly valuable tool for studying the potential effects of land-use and land-cover changes on the near-surface atmosphere since the atmosphere and biosphere are allowed to dynamically interact through the surface and canopy energy balance. GEMRAMS is a coupled atmospheric-biospheric model comprised of an atmospheric model, RAMS, and an ecophysiological process-based model, GEMTM. In the first part of this study, the soil-vegetation-atmosphere-transfer (SVAT) scheme, LEAF2, from RAMS, coupled with GEMTM, are used to simulate energy, water and carbon fluxes over different cropping systems (winter wheat and irrigated corn) and over a mixed C3/C4 shortgrass prairie located at the USDA-ARS Central Plains Experimental Range near Nunn, Colorado, the LTER Shortgrass Steppe site. The new SVAT scheme, GEMLEAF, is forced with air temperature and humidity, wind speed and photosynthetic active radiation (PAR). Calculated canopy temperature and relative humidity, soil moisture and temperature and PAR are used to compute sunlit/shaded leaf photosynthesis (for C3 and C4 plant types) and respiration. Photosynthate is allocated to leaves, shoots, roots and reproductive organs with variable partition coefficients, which are functions of soil water conditions. As water stress increases, the fraction of photosynthate allocated to root growth increases. Leaf area index (LAI) is estimated from daily leaf biomass growth, using the vegetation-prescribed specific leaf area. Canopy conductance, computed and based on photosynthesis and relative humidity, is used to calculate latent heat flux. Simulated energy and CO₂ fluxes are compared to observations collected using Bowen ratio flux towers during two growing seasons. Seasonality of the fluxes reflecting different plant phenologies agrees well with the observed patterns. In the second part of this study, simulations for two clear days are performed with GEMRAMS over a model domain centered at the SGS site. Simulated spatial differences in the energy fluxes can be associated with the highly heterogeneous landscape in this area.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0400 BIOGEOSCIENCES
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1632 Land cover change
DE: 1833 Hydroclimatology
SC: Biogeosciences [B]
MN: Fall Meeting 2005