Spatial-temporal variations in evapotranspiration across the continental United States: An atmospheric water balance perspective

Accurate estimation of terrestrial evapotranspiration (ET) is crucial for understanding land-atmosphere interactions, but is challenging on the regional scales. The water balance approach, including terrestrial and atmospheric water balance (TWB and AWB), provides a simple tool for estimating regional ET. This study estimated ET values based on the AWB approach (ETAWB) AWB ) over the continental United States (CONUS) for the period 1979-2021. Validations using TWB-based ET estimates (ETTWB) TWB ) suggest that ET AWB is accurate. ET AWB demonstrates comparable interannual variability with the other three long-term ET products over the CONUS and is consistent with ET TWB in the majority of basins. The 43-year CONUS averaged ET AWB is 548 +/- 26 mm/ year, with higher values in the eastern region and the coastal regions in the western CONUS, and lower values in the western arid regions. During 1979-2021, increasing trends of ET AWB are observed in the eastern CONUS, while decreasing trends occurred in the western regions. The intercomparison between ETAWB, AWB , GLEAM, Noah, and ERA5 illustrates similar spatial patterns and linear trends. In the water-limited arid basins, ET AWB anomalies over time show strong agreements with precipitation anomalies. The results of this study indicate that the AWB approach provides reasonable regional-to-continental terrestrial ET estimates over the CONUS, serving as a reference for hydrological and climatic modeling.