HR: 0800h
AN: B31B-0215    [Abstracts]
TI: Comparative Analysis of AVHRR and MODIS NDVI Time Series for Developing Long Term Records of Terrestrial Vegetation
AU: * Dwyer, J
EM: dwyer@usgs.gov
AF: SAIC, EROS Data Center, Sioux Falls, SD 57198 United States
AU: Reed, B
EM: reed@usgs.gov
AF: SAIC, EROS Data Center, Sioux Falls, SD 57198 United States
AU: Ji, L
EM: lji@usgs.gov
AF: Colorado State University, EROS Data Center, Sioux Falls, SD 57198 United States
AU: Gallo, K
EM: kgallo@usgs.gov
AF: National Oceanic & Atmospheric Administration, EROS Data Center, Sioux Falls, SD 57198 United States
AU: Eidenshink, J
EM: eidenshink@usgs.gov
AF: U.S. Geological Survey, EROS Data Center, Sioux Falls, SD 57198 United States
AB: Long-term continuity of the moderate resolution satellite data record is critical for documenting effects on the land surface that may be related to anthropogenic influences or climate variability. Since the data record began with the advanced very high resolution radiometer (AVHRR) in the 1980's and continued to the moderate resolution imaging spectroradiometer (MODIS) beginning in 2000, variations in the satellite signal may be attributed to changes in both the imaging platform and imaging sensor. The US Geological Survey Earth Resources Observation Systems (EROS) Data Center (EDC) has created contemporaneous data sets of AVHRR and MODIS vegetation indices from 2001 through 2003 in order to characterize and resolve differences in the instrument signals and derived indices to ensure the continuity of a long-term record or vegetation state and condition. The comparison data sets consist of 16-day normalized difference vegetation index (NDVI) at 1-kilometer resolution data covering the conterminous United States. Early results indicate strong agreement (r2 = 0.92) between the AVHRR and MODIS NDVI over the data set as a whole, although agreement may be weaker for specific land cover types, such as southeastern evergreen needle-leaf forest (r2 = 0.65). While there is generally very strong agreement between the AVHRR and MODIS NDVI, phenological metrics derived from each data set exhibited significant differences that were attributed to aerosol corrections in the MODIS VI data. In the case of the MODIS NDVI data, considerable post-processing and analysis of the embedded quality assessment information is necessary in order to determine whether departures from the corresponding AVHRR NDVI records are due to differences in radiometric response of the instruments, methods of atmospheric correction, cloud cover assessment, or decision rules for constructing image composites.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting