Water balance‐based actual evapotranspiration reconstruction from ground and satellite observations over the conterminous United States

Abstract

The objective of this study is to produce an observationally based monthly evapotranspiration (ET) product using the simple water balance equation across the conterminous United States (CONUS). We adopted the best quality ground and satellite-based observations of the water budget components, i.e., precipitation, runoff, and water storage change, while ET is computed as the residual. Precipitation data are provided by the bias-corrected PRISM observation-based precipitation data set, while runoff comes from observed monthly streamflow values at 592 USGS stream gauging stations that have been screened by strict quality controls. We developed a land surface model-based downscaling approach to disaggregate the monthly GRACE equivalent water thickness data to daily, 0.1258 values. The derived ET computed as the residual from the water balance equation is evaluated against three sets of existing ET products. The similar spatial patterns and small differences between the reconstructed ET in this study and the other three products show the reliability of the observationally based approach. The new ET product and the disaggregated GRACE data provide a unique, important hydro-meteorological data set that can be used to evaluate the other ET products as a benchmark data set, assess recent hydrological and climatological changes, and terrestrial water and energy cycle dynamics across the CONUS. These products will also be valuable for studies and applications in drought assessment, water resources management, and climate change evaluation.

Mapped Hydroclimatology of Evapotranspiration and Drainage Runoff Using SMAP Brightness Temperature Observations and Precipitation Information

“…The hydroclimatology of summer season mean ET transitions from lower values in the west (<1 mm/day) to larger values in the east and south east (>4 mm/day), Figure 5a. This spatial pattern is expected and consistent with other observation based ET estimates such as (Wan et al, 2015;. The observed hydroclimatology in Figure 5a raises a key question: Is the magnitude of E c ET h i also consistent with independent and direct measurements in terms of bias and proportionality?…”

Estimating annual water storage variations in medium-scale (2000–10 000 km&lt;sup&gt;2&lt;/sup&gt;) basins using microwave-based soil moisture retrievals

“…Therefore, additional validation work over a wider variety of conditions is certainly required. Likewise, an objective intercomparison between this approach and earlier downscaling approaches based on higher-resolution land surface model output (e.g., Reager et al, 2015;Wan et al, 2015) is warranted.…”

“…This has spurred interest in the development of spatial downscaling techniques for GRACEbased dS / dt. These approaches have generally been based on the use of (relatively) higher-resolution water storage predictions obtained from distributed land surface model predictions (Reager et al, 2015;Wan et al, 2015) or a combination of land surface model output and independent evapotranspiration (E T ) and precipitation (P ) flux estimates (Ning et al, 2014). In contrast, microwave-based surface soil moisture (θ ) retrievals provide a direct assessment of soil water storage that can be obtained at relatively finer resolutions (typically ∼ 1000 km 2 ).…”

Assessment of Physical Water Scarcity in Africa Using GRACE and TRMM Satellite Data

“…Besides, at the basin scale, solving the water balance equation can lead to isolating either the runoff (river discharge) [32,40,41] or the evapotranspiration [42][43][44][45].…”