HR: 0800h
AN: H41A-0402    [Abstracts]
TI: Validation of ET maps derived from MODIS imagery
AU: * Hong, S
EM: hong@nmt.edu
AF: New Mexico Tech, 801 Leroy place, Socorro, NM 87801 United States
AU: Hendrickx, J M
EM: hendrick@nmt.edu
AF: New Mexico Tech, 801 Leroy place, Socorro, NM 87801 United States
AU: Borchers, B
EM: borchers@nmt.edu
AF: New Mexico Tech, 801 Leroy place, Socorro, NM 87801 United States
AB: In previous work we have used the New Mexico Tech implementation of the Surface Energy Balance Algorithm for Land (SEBAL-NMT) for the generation of ET maps from LandSat imagery. Comparison of these SEBAL ET estimates versus ET ground measurements using eddy covariance showed satisfactory agreement between the two methods in the heterogeneous arid landscape of the Middle Rio Grande Basin. The objective of this study is to validate SEBAL ET estimates obtained from MODIS imagery. The use of MODIS imagery is attractive since MODIS images are available at a much higher frequency than LandSat images at no cost to the user. MODIS images have a pixel size in the thermal band of 1000x1000 m which is much coarser than the 60x60 m pixel size of LandSat 7. This large pixel size precludes the use of eddy covariance measurements for validation of ET maps derived from MODIS imagery since the eddy covariance measurement is not representative of a 1000x1000 m MODIS pixel. In our experience, a typical foot print of an ET rate measured by eddy covariance on a clear day in New Mexico around 11 am is less than then thousand square meters or two orders of magnitude smaller than a MODIS thermal pixel. Therefore, we have validated ET maps derived from MODIS imagery by comparison with up-scaled ET maps derived from LandSat imagery. The results of our study demonstrate: (1) There is good agreement between ET maps derived from LandSat and MODIS images; (2) Up-scaling of LandSat ET maps over the Middle Rio Grande Basin produces ET maps that are very similar to ET maps directly derived from MODIS images; (3) ET maps derived from free MODIS imagery using SEBAL-NMT can provide reliable regional ET information for water resource managers.
DE: 1813 Eco-hydrology
DE: 1814 Energy budgets
DE: 1840 Hydrometeorology
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1855 Remote sensing (1640)
SC: Hydrology [H]
MN: Fall Meeting 2005