Evaluation of a CONUS-wide ECOSTRESS DisALEXI evapotranspiration product

The Atmosphere-Land Exchange Inverse disaggregation (DisALEXI) algorithm is a multi-scale energy balance model that estimates evapotranspiration (ET) using land-surface temperature (LST) as a driving remote sensing input. ECOSTRESS is a thermal radiometer mounted on the International Space Station (ISS), and provides near-daily overpass over sites spread throughout the contiguous United States (CONUS). Using LST products from ECOSTRESS, DisALEXI daily (24hr) ET products have been produced over CONUS with 70m resolution and sub-weekly timesteps. This new product was evaluated at 17 CONUS flux sites over a variety of landcover types, yielding accuracies with R2 = 0.8 and RMSE = 0.81 mm/day, which is comparable to previous DisALEXI validation studies. This work extends DisALEXI spatial coverage, and shows that the algorithm is valid over a larger segment of the contiguous United States. This validation also shows the impact of quality flags, as pixels with high view zenith angles or high aerosol optical depth showed greater deviation from field measurements. As a product demonstration, we show a regional map of fine-scale ET, where the fine-scale variation over wider areas can detect small areas of stress much sooner than products with coarse resolution representing average conditions.