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Journal ArticleDOI

A phenomenological model of soil evaporative efficiency using surface soil moisture and temperature data

TL;DR: In this article, a parsimonious model is developed to estimate soil evaporative efficiency (SEE) defined as the ratio of actual to potential soil evaporation, using a soil resistance driven by surface moisture, meteorological forcing and time (hour) of day, and has the capability to be calibrated using the radiometric surface temperature derived from remotely sensed thermal data.
About: This article is published in Agricultural and Forest Meteorology.The article was published on 2018-06-15 and is currently open access. It has received 26 citations till now. The article focuses on the topics: Water content & Correlation coefficient.

Summary (1 min read)

1. Introduction

  • The new resistance model is tested in terms of SEE estimates using eddy covariance measurements collected over a bare soil site in central Morocco, and its performance is assessed against two benchmark models.
  • Calibration capabilities of the SEE model from thermal (instead of eddy covariance) data are also investigated.

4. Calibration strategies

  • The calibrated τ hyst is equal to minus the inverse of the slope of the relationship between δSEE/δt and the daily mean SEE (see Equation 7).
  • In fact, such a hypothesis relies on the above linearity assumptions.
  • As a linearity assessment of the SEE t (δt) relationship, the coefficient of determination (ordinary R-squared) between EC-derived SEE and time of day is estimated as 0.99 and 0.93 for the wet and dry date of Figure 5 respectively.
  • The R-squared is slightly degraded to 0.93 and 0.73 respectively for the TI case, due to larger uncertainties in TI-derived SEE estimates.

5.1.3. Evaporation results

  • Respectively) are more accurate than TI-derived parameters, the temporal variability in retrieved parameters (19% and 40%, respectively) remains larger, i.e. calibration using TI data is still effective and meaningful.
  • Such results further confirm the consistency between TI-and EC-derived SEE estimates when LEp > 400 Wm −2 .

5.3. Applicability to temporally-sparse thermal data

  • The mean root mean square error (RMSE) between simulated and EC-derived LE is about 60, 50 and 40 Wm −2 for the S92, M16 and TI-based calibration strategy, respectively.
  • Such results emphasize the utility of calibrating evaporation models using thermal data, even when TI data are temporally sparse.

6. Conclusions and perspectives

  • In fact, the model calibration over areas of agricultural or ecological interest requires remote sensing data at high spatio-temporal resolution (Lagouarde et al., 2013, e.g.) .
  • As a long-term vision, the integration of the r ss parameterization in state-of-the-art dual-source surface models (Norman et al., 1995, e. g.) has great potential to help separate soil evaporation and plant transpiration components of agricultural crops (Merlin et al., 2014, e.g.) , and hence to better assess the crop water use efficiency.
  • Under vegetated surface, soil evaporation would be affected not only by the soil available energy but also by the heat and vapor transfer coefficients between the soil, vegetation and atmosphere (Shuttleworth and Wallace, 1985; Haghighi and Or, 2015) .
  • In the recent study of Hssaine et al. (2018) , the soil resistance's parameters were calibrated over partially covering wheat by implementing a network of soil, vegetation and air resistances and by separating phenological stages with fractional vegetation cover smaller and larger than 0.5.

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Journal ArticleDOI
TL;DR: In this article, the authors review current progress in partitioning E and transpiration and provide a prospectus for how to improve theory and observations going forward, and demonstrate that optimal ecosystem response to D is a reasonable assumption, in agreement with recent studies.
Abstract: . Evaporation ( E ) and transpiration ( T ) respond differently to ongoing changes in climate, atmospheric composition, and land use. It is difficult to partition ecosystem-scale evapotranspiration (ET) measurements into E and T , which makes it difficult to validate satellite data and land surface models. Here, we review current progress in partitioning E and T and provide a prospectus for how to improve theory and observations going forward. Recent advancements in analytical techniques create new opportunities for partitioning E and T at the ecosystem scale, but their assumptions have yet to be fully tested. For example, many approaches to partition E and T rely on the notion that plant canopy conductance and ecosystem water use efficiency exhibit optimal responses to atmospheric vapor pressure deficit ( D ). We use observations from 240 eddy covariance flux towers to demonstrate that optimal ecosystem response to D is a reasonable assumption, in agreement with recent studies, but more analysis is necessary to determine the conditions for which this assumption holds. Another critical assumption for many partitioning approaches is that ET can be approximated as T during ideal transpiring conditions, which has been challenged by observational studies. We demonstrate that T can exceed 95 % of ET from certain ecosystems, but other ecosystems do not appear to reach this value, which suggests that this assumption is ecosystem-dependent with implications for partitioning. It is important to further improve approaches for partitioning E and T , yet few multi-method comparisons have been undertaken to date. Advances in our understanding of carbon–water coupling at the stomatal, leaf, and canopy level open new perspectives on how to quantify T via its strong coupling with photosynthesis. Photosynthesis can be constrained at the ecosystem and global scales with emerging data sources including solar-induced fluorescence, carbonyl sulfide flux measurements, thermography, and more. Such comparisons would improve our mechanistic understanding of ecosystem water fluxes and provide the observations necessary to validate remote sensing algorithms and land surface models to understand the changing global water cycle.

159 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide a brief account of the key milestones in the history of remote sensing ET model development in two categories: temperature-based and conductance-based models, and make the following recommendations for future work: (1) improving key remote sensing products needed for ET mapping purposes, including soil moisture, foliage clumping index, and leaf carboxylation rate, (2) combining temperature-and conductancebased models for regional ET estimation, (3) refining methodologies for tight coupling between carbon and water cycles, (4) fully utilizing vegetation structural and

126 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared four different methods based on eddy covariance, sap flow and lysimetry measurements and FAO modeling to estimate the evapotranspiration partitioning of wheat crop.

54 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an approach to estimate the timing and the amount of irrigation throughout the agricultural season using optical and thermal Landsat-7/8 data, which is implemented in four steps: i) partitioning the Landsat land surface temperature (LST) to derive the crop water stress coefficient (Ks), ii) estimating the daily root zone soil moisture (RZSM) from the integration of Landsat derived Ks into a crop water balance model, iii) retrieving irrigation at the pixel scale and iv) aggregating pixel-scale irrigation estimates at

38 citations

Journal ArticleDOI
TL;DR: In this article, the authors systematically evaluated the differences in ecosystem fluxes between morning and afternoon, using half-hourly and hourly data from 82 eddy-covariance sites in the FLUXNET2015 Tier 1 dataset.

36 citations

References
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Journal ArticleDOI
TL;DR: In this article, a simple two-parameter model was developed that relates mean annual evapotranspiration to rainfall, potential evapOTranspiration, and plant-available water capacity.
Abstract: It is now well established that forested catchments have higher evapotranspiration than grassed catchments. Thus land use management and rehabilitation strategies will have an impact on catchment water balance and hence water yield and groundwater recharge. The key controls on evapotranspiration are rainfall interception, net radiation, advection, turbulent transport, leaf area, and plant-available water capacity. The relative importance of these factors depends on climate, soil, and vegetation conditions. Results from over 250 catchments worldwide show that for a given forest cover, there is a good relationship between long-term average evapotranspiration and rainfall. From these observations and on the basis of previous theoretical work a simple two-parameter model was developed that relates mean annual evapotranspiration to rainfall, potential evapotranspiration, and plant-available water capacity. The mean absolute error between modeled and measured evapotranspiration was 42 mm or 6.0%; the least squares line through the origin had as lope of 1.00 and a correlation coefficient of 0.96. The model showed potential for a variety of applications including water yield modeling and recharge estimation. The model is a practical tool that can be readily used for assessing the long-term average effect of vegetation changes on catchment evapotranspiration and is scientifically justifiable.

2,191 citations

Journal ArticleDOI
TL;DR: In this paper, a one-dimensional model is adopted to describe the energy partition of sparse crops, and a combination equation which describes evaporation in terms of controlling resistances associated with the plants, and with the soil or water in which they are growing.
Abstract: SUMMARY A one-dimensional model is adopted to describe the energy partition of sparse crops. Theoretical development of this model yields a combination equation which describes evaporation in terms of controlling resistances associated with the plants, and with the soil or water in which they are growing. The equation provides a simple but physically plausible description of the transition between bare substrate and a closed canopy. Although the aerodynamic transfer resistances for incomplete canopies have, as yet, no experimental justification, typical values, appropriate to a specimen agricultural crop and soil, are shown to have limited sensitivity in the model. Processes which require further study if the equation is to be used to calculate evaporation throughout a crop season are also discussed. Previous steps in the development of a physically based model of the vegetationatmosphere interaction (e.g. Shuttleworth 1976, 1978) explicitly treat the vegetation as a closed, stable canopy of uniform structure. They emphasize the interaction of the vegetation, with fluxes arising at the soil surface introduced as an unspecified, and implicitly small, input to the model (Shuttleworth 1979). In this paper this theoretical work is reinterpreted and developed into the situation of sparse crops, where the use of a one-dimensional model has less obvious justification. In describing such crops the soil and plant components must carry equal status, since they can be of similar size and their relative importance can change significantly with crop cover. The philosophy of this paper is to make minimum concession to the more obvious three-dimensional structure of sparse and row crops. Accordingly a one-dimensional model of the interaction is adopted to derive a combination equation, which can provide a physically plausible transition between the bare substrate and closed canopy limits. The equation is expressed in terms of conceptual resistances now familiar to the micrometeorologist and plant physiologist: canopy resistance and boundary layer resistance etc; it also requires the less familiar concept of a surface resistance for bare soil (Monteith 1981). In the later sections of the paper typical values of these resistances are used to illustrate how energy partition varies between crops of the same height, but with different leaf areas.

1,482 citations


"A phenomenological model of soil ev..." refers background in this paper

  • ...Under vegetated surface, soil665 evaporation would be affected not only by the soil available energy but also666 by the heat and vapor transfer coefficients between the soil, vegetation and667 atmosphere (Shuttleworth and Wallace, 1985; Haghighi and Or, 2015)....

    [...]

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TL;DR: In this paper, a two-layer model of turbulent exchange that includes the view geometry associated with directional radiometric surface temperature is developed and evaluated by comparison of model predictions with field measurements.

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"A phenomenological model of soil ev..." refers background in this paper

  • ...…the top few mil-60 limeters of soil which inhibits evaporation, regardless of the availability of the61 soil water underneath (Mahrt and Pan, 1984; Dickinson et al., 1986; Soarès62 et al., 1988; Wetzel and Chang, 1988; Van de Griend and Owe, 1994; Heitman63 et al., 2008; Shahraeeni et al., 2012)....

    [...]

  • ...…is added to rss,M16 to account for diurnal130 variations in SEE associated with top-soil drying (receding evaporation131 front) during daytime (Mahrt and Pan, 1984; Dickinson et al., 1986;132 Soarès et al., 1988; Wetzel and Chang, 1988; Van de Griend and Owe,133 1994; Heitman et al., 2008;…...

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TL;DR: In this article, a derivation for the effective atmospheric emissivity to predict downcoming long-wave radiation at ground level under a clear sky and for a nearly standard atmosphere is presented.
Abstract: A derivation is presented for the effective atmospheric emissivity to predict downcoming long-wave radiation at ground level under a clear sky and for a nearly standard atmosphere. The results are in good agreement with those obtainable with empirical formulae based on water vapor pressure and temperature. However, the proposed formulation has the advantage that its simple functional form is based on physical grounds without the need for empirical parameters from radiation measurements. Also, in contrast to the empirical equations, it may be adjusted in a simple way to reflect changes in climatic and atmospheric conditions.

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"A phenomenological model of soil ev..." refers background in this paper

  • ...In general, state-of-the-art models rely on specific assump-30 tions on either the soil evaporation (Caparrini et al., 2004)or the plant tran-31 spiration (Kustas and Norman, 1999), or base their two-source representation32 on semi-empirical or semi-physical resistances....

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Q1. What are the contributions in "A phenomenological model of soil evaporative efficiency using surface soil moisture and temperature data" ?

In this paper, a parsimonious model is developed to estimate soil evaporative efficiency ( SEE ) defined as the ratio of actual to potential soil evaporation.