Evapotranspiration between satellite overpasses: methodology and case study in agricultural dominant semi-arid areas

Abstract

A backward‐averaged iterative two‐source surface temperature and energy balance solution (BAITSSS) algorithm was developed to estimate evapotranspiration (ET) during the period between Landsat satellite overpass dates. The METRIC (mapping evapotranspiration at high resolution with internalized calibration) model was used to estimate ET using short wave and thermal data from the Landsat images. METRIC generated ET was used to define initial surface characteristics, soil water conditions and initialize the soil water content for the surface and root zone at the start of the simulation period, and to adjust the results from BAITSSS at the next satellite overpass date if needed. North American Regional Reanalysis (NARR) weather data were used to estimate the surface energy balance components in between the satellite overpasses. The fraction of vegetation cover (fc) was used to partition surface energy balance components, as defined by the normalized difference vegetation index. Soil surface resistance (rss) and Jarvis‐model‐type canopy resistance (rsc) were used to calculate latent heat flux using the aerodynamic equations. A water balance was implemented to track the water content at the surface and root zone. An irrigation sub‐model was developed to consider the role of irrigation for known irrigated agricultural fields, which is critical when computing ET in an agriculture‐dominant area. Any mismatch between the estimated and METRIC ET at the next satellite overpass can be adjusted back over the simulation period with a time‐based linear correction to increase the accuracy and reduce computation time. In this study, BAITSSS results from southern Idaho and northern California are presented for 3 h time steps.

Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations

“…Earlier studies indicate that ET r F needs to be adjusted in particular crops like olive orchards which behave similarly to the grass-based coefficients [34,35] because of the crop stress, physiological and micrometerological variations. To address this problem, Dhungel et al [54] developed a backward-averaged iterative two-source surface temperature and energy balance solution algorithm (BAITSSS), incorporating the crop and soil stress components using soil water balance, to capture the impacts of the irrigation and precipitation between the satellite overpass. They demonstrated improved robustness compared with mathematical and regression based interpolations.…”

Evaluation of Landsat-Based METRIC Modeling to Provide High-Spatial Resolution Evapotranspiration Estimates for Amazonian Forests

“…Other methods for interpolating between image dates have been provided by e.g., [39,[42][43][44][45]. Applying a cubic spline function may introduce some uncertainty into the estimation of monthly or longer ET estimates.…”

An Intercomparison of Satellite-Based Daily Evapotranspiration Estimates under Different Eco-Climatic Regions in South Africa

“…These include the integration of the feedback method that uses the complimentary relationship between actual ET and pan ET [60], data fusion methods (i.e., combining different data sources) [61,62], and the backward-averaged iterative two-source surface temperature and energy balance solution (BAITSSS) algorithm [63].…”