HR: 0800h
AN: A41C-0063    [Abstracts]
TI: Temporal Interpolation of Satellite Vegetation Imagery and its Influence on Simulated Seasonal Carbon Uptake by Vegetation in the Middle Latitudes.
AU: * Philpott, A W
EM: andrew@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523 United States
AU: Denning, A
EM: denning@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523 United States
AU: Conner Gausepohl, S L
EM: sheri@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523 United States
AU: Baker, I
EM: baker@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523 United States
AU: Brown, M E
EM: molly.brown@gsfc.nasa.gov
AF: Science Systems and Applications, NASA-Goddard Space Flight Center. Code 614.4, Greenbelt, MD 20771 United States
AU: Schaefer, K
EM: kevin.schaefer@noaa.gov
AF: Climate Monitoring and Diagnostics Laboratory R/CMDL1, 325 Broadway, Boulder, CO 80305 United States
AB: Normalized Difference Vegetation Index (NDVI) is used in the Simple Biosphere (SiB) model to specify vegetation parameters such as fraction of absorbed photosynthetically active radiation (FPAR) and leaf area index (LAI), which are in turn used in the calculation of surface fluxes of carbon dioxide, water vapor, and sensible heat. The seasonal cycle of NDVI is therefore an important driver in the simulated seasonal cycle of CO2 flux and bowen ratio in global, regional, and single-site simulations. Previous studies have shown that the SiB seasonal flux cycle, has inconsistencies with data at particular sites, such as the WLEF-TV tower in Wisconsin, USA. One possible cause is the interpolation of NDVI from monthly maximum value composites to daily values, which assumes that the monthly NDVI occurs at the middle of the month. This causes NDVI to be overestimated in the spring and fall, when the acutal maximum value occurs near the beginning or end of the month. An alternative interpolation regime seeks to better assign the date of maximum NDVI, using the slope and curvature of the monthy NDVI timeseries. This alternative interpolation method better estimated 8km 15-day maximum value GIMMSg data from monthly maximum values in North America, particulary in northern temperate and boreal latitudes. The GIMMSg 15-day data includes the date on which each observation occured, which is ideal for evaluating the SiB interpolation method. The new interpolation method also improved SiB surface fluxes at a number of North American tower sites, compared to eddy covariance data. These changes also impact global and regional simulations.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005