Applications of the Newly Improved Global MOD16 Evapotranspiration Algorithm at Fluxnet Tower Sites and global scale
Qiaozhen
Mu, University of Montana, qiaozhen@ntsg.umt.edu
(Presenting)
Maosheng
Zhao, University of Montana, zhao@ntsg.umt.edu
Steven
W.
Running, University of Montana, swr@ntsg.umt.edu
We have improved the MOD16 ET algorithm based on Mu et al.’s 2007 and Cleugh et al.'s 2007 Penman–Monteith based ET algorithms. The improved ET algorithm has new modules such as canopy evaporation, wet ground evaporation and soil heat flux. Also, the improved ET estimates ET both at daytime and nighttime. We evaluated the improved algorithm using ETobservations at 68 Fluxnet eddy covariance flux towers. We calculated ET with both the beta algorithm (Mu et al., 2007) and the improved algorithm using Global Modeling and Assimilation Office (GMAO v. 4.0.0) meteorological data and compared the resulting ET estimates with observations. MODIS version 5 LAI/FPAR and version 4 albedp were used as inputs to both algorithms. Results indicate that the improved ET algorithm substantially reduces the root mean square error (RMSE) of the daily ET averaged over the 68 towers from 1.3 mm/day (beta version) to 0.9 mm/day (improved version) with tower meteorological data, and about the same at 0.9 mm/day with GMAO meteorological data. The average ET bias of the tower-driven ET estimates to the ET observations changed from -0.3 mm/day to 0.1 mm/day and from -0.3 mm/day to 0.2 mm/day driven by GMAO data. The correlation coefficients between the ET observations and tower-driven algorithm estimates increases from R2=0.40 (beta version) to R2=0.73 (improved version. Comparison of tower data with results driven by the GMAO meteorology resulted in correlations of R2=0.73 (improved version) relative to R2=0.66 (beta version). We then applied the improved ET algorithm globally at 1km resolution and compared the results with precipitation. The ET estimates have at the arid region have been increased a lot. Most of the precipitation at the arid regions is lost through ET.
Presentation Type: Poster
Poster Session: Ecosystems Science
NASA TE Funded Awards Represented:
Running, Steven
Validation, improvement and applications of MODIS global terrestrial primary production MOD 17 and a test MODIS evapotranspiration product: Green Compute Cluster