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Fundamental process understanding and description of heat, mass, and momentum exchanges across the land-atmosphere interface in model boundary forcing parameterizations is critical to the simulation of near-surface soil moisture dynamics (e.g., bare-soil evaporation). This study explores the sensitivity of a continuum-scale porous media heat and mass transfer model to the spatial-discretization length-scales (i.e., spatial-resolution) of near-surface atmospheric data; the goal is to determine how much data are needed to force the model and adequately capture evaporative water losses and subsurface state variable distributions. The requisite atmospheric forcing data were taken from the high-resolution, precision bare-soil evaporation experiments of Trautz et al. (2018, https://doi.org/10.1029/2018WR023102). Simulation results demonstrated that shallow subsurface mass and heat transfer dynamics can be adequately captured with forcing data averaged over large length-scales, or a minimal number of measurements, provided that soil conditions are properly described. The soil moisture spatial distributions were found to be insensitive to horizontal variations in the forcing data. The model failed to capture small-scale trends observed experimentally; this did not impact the accuracy of total evaporative water loss estimates however. These results indicate that in future physical experimental efforts conducted at 1–10-m length-scales, there is no need to focus on the generation of high-spatial resolution atmospheric measurements—time and effort would be better spent in characterizing soil conditions and properties. Even though a theoretical foundation was not provided to directly extrapolate this work to the field scale, these findings have practical value in designing field data collection strategies.

Fundamental process understanding and description of heat, mass, and momentum exchanges across the land‐atmosphere interface in model boundary forcing parameterizations is critical to the simulation of near‐surface soil moisture dynamics (e.g., bare‐soil evaporation). This study explores the sensitivity of a continuum‐scale porous media heat and mass transfer model to the spatial‐discretization length‐scales (i.e., spatial‐resolution) of near‐surface atmospheric data; the goal is to determine how much data are needed to force the model and adequately capture evaporative water losses and subsurface state variable distributions. The requisite atmospheric forcing data were taken from the high‐resolution, precision bare‐soil evaporation experiments of Trautz et al. (2018, https://doi.org/10.1029/2018WR023102). Simulation results demonstrated that shallow subsurface mass and heat transfer dynamics can be adequately captured with forcing data averaged over large length‐scales, or a minimal number of measurements, provided that soil conditions are properly described. The soil moisture spatial distributions were found to be insensitive to horizontal variations in the forcing data. The model failed to capture small‐scale trends observed experimentally; this did not impact the accuracy of total evaporative water loss estimates however. These results indicate that in future physical experimental efforts conducted at 1–10‐m length‐scales, there is no need to focus on the generation of high‐spatial resolution atmospheric measurements—time and effort would be better spent in characterizing soil conditions and properties. Even though a theoretical foundation was not provided to directly extrapolate this work to the field scale, these findings have practical value in designing field data collection strategies. Key Points: System surface condition‐dependent coupling strength should be considered when conducting atmospheric sampling and soil characterizationHigh spatial resolution forcing data are not needed for reproducing evaporation dynamics at the continuum scale for simple soil surface conditions [ABSTRACT FROM AUTHOR]

A combined heat-pulse and sensible heat balance method can be used to determine evaporation using temperature measurements and thermal property estimations. The objective of this study was to investigate the applicability of the combined heat-pulse and sensible heat balance method by comparing laboratory experimental data to both an analytical and a multiphase heat and mass transfer model. A bench-scale laboratory experiment was performed to measure soil thermal and hydraulic properties at ine spatial and temporal resolutions. Comparisons of experimental and numerical results conirmed the applicability of the heat-pulse and sensible heat balance methods to determine evaporation rates. Results showed close agreement with experimental water loss measurements. This study demonstrated the ability and versatility of using the heat-pulse and sensible heat balance methods in numerical heat and mass transfer models to determine evaporation rates. Calculated soil thermal properties were in 93.4 and 97.5% agreement with experimental results for water content values >0.05. Deviations were observed at low water contents due to sensor sensitivity. The calculated evaporation rates yielded cumulative water losses that were 96.8 and 97.7% in agreement with experimentally measured weight loss data. Late Stage 1 evaporation was overestimated due to observed temperature rises by two of the heat-pulse probes. Despite this, the combined heat-pulse and sensible heat balance method is a powerful tool that can be used to determine evaporation rates in situ. [ABSTRACT FROM AUTHOR]