92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Tuesday, 24 January 2012: 9:00 AM
Development of a High Spatial and Temporal Resolution Evapotranspiration Product Through Integration of Landsat and MODIS Land Surface Data [INVITED]
Room 352 (New Orleans Convention Center )
Terri S. Hogue, UCLA, Los Angeles, CA; and J. Kim

Routine monitoring of evapotranspiration (ET) at high spatial resolutions has generally not been feasible due to the long repeat cycle of satellites that contain high spatial resolution sensors (i.e., Landsat, ASTER and Quickbird, etc). Consequently, high temporal resolution (daily or more frequent) but moderate spatial resolution satellites (i.e., MODIS, AVHRR and GOES, etc) have been typically used to formulate ET algorithms. Consequently, we have undertaken development of a method that provides high spatial (~30m) and temporal (~daily) ET estimates by combining the advantages from Landsat and MODIS satellite systems. The developed ET model is based on the commonly applied surface temperature-vegetation index (Ts-VI) triangle method and development of an evaporative fraction. Prior to applying the ET model, Ts and VI are obtained by disaggregating relevant MODIS images to the Landsat scale by using a subtraction method that applies the difference between two MODIS images to subsequent Landsat images, producing sub-pixel variability within the MODIS pixel. Another key input (net radiation) is obtained from a previously developed MODIS-based net radiation model. The daily, 30m ET estimate is formulated completely from remote sensing data and does not require ground-based observations for implementation. Evaluation of the ET product is undertaken at select flux tower sites in southeastern Arizona. The ET model validates well over the tested sites and captures regional details not observable in lower spatial resolution products. Algorithm improvement is ongoing to reduce uncertainties over some biomes, primarily related to MODIS temperature biases. The near real-time, high resolution ET model shows strong potential for use over heterogeneous and complex terrain and can facilitate improved regional water budget investigations, agricultural studies, hydrologic model validation and operational forecasting.

Supplementary URL: