On water vapor transport in field soils

Cahill, A. T.; Parlange, M. B.

doi:10.1029/97wr03756

Cited by 168 publications

(87 citation statements)

References 20 publications

(7 reference statements)

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“…4). The time scale of thermal property measurements (each 4 h) prevents close examination of diurnal patterns, but thermal properties generally decreased from midmorning through afternoon and increased from late evening through early morning, which is consistent with diurnal cycling in near-surface soil water content observed by others (Rose 1968;Jackson 1978;Cahill and Parlange 1998). The observed diurnal variation was typically Ͻ8% of the daily mean value for both and C.…”

Section: February 2008 N O T E S a N D C O R R E S P O N D E N C Ementioning

confidence: 48%

Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics

Heitman

Horton

DeSutter

2008

Journal of Hydrometeorology

101

109

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Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soilwater evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patterns. Immediately after rainfall, evaporation occurred near the soil surface. Within 6 days after rainfall, the evaporation zone proceeded > 13 mm into the soil profile. Evaporation rates at the 3-mm depth reached peak values > 0.25 mm h −1 . Evaporation occurred simultaneously at multiple measured depth increments, but with time lag between peak evaporation rates for depths deeper below the soil surface. Implementation of finescale measurement techniques for the soil sensible heat balance provides a new opportunity to improve understanding of soil-water evaporation. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. ABSTRACT Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/ drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patte...

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Section: February 2008 N O T E S a N D C O R R E S P O N D E N C Ementioning

confidence: 48%

Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics

Heitman

Horton

DeSutter

2008

Journal of Hydrometeorology

101

109

View full text Add to dashboard Cite

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“…This is important because the hydraulic conductivity versus the soil moisture potential curve is highly nonlinear and, therefore, the flow of soil moisture from the upper layer to the lower layer in a wet period leads to a large decrease in hydraulic conductivity and liquid water distribution [26,31], while during the dry period, the soil moisture was more constant along the depths with less dependence on the liquid fraction. The soil moisture content fluctuated through the day according to the vapor flux as reported previously [38][39][40]. As such, improvements in the model's representation of both soil moisture and soil moisture potential in order to have an optimal simulation output.…”

Section: Soil Temperature and Soil Moisturementioning

confidence: 99%

Evapotranspiration in Northern Agro-Ecosystems: Numerical Simulation and Experimental Comparison

Ruairuen¹,

Fochesatto²,

Bittelli³

et al. 2017

Current Perspective to Predict Actual Evapotranspiration

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Evapotranspiration and near-surface soil moisture dynamics are key-entangled variables regulating flux at the surface-atmosphere interface. Both are central in improving mass and energy balances in agro ecosystems. However, under the extreme conditions of high-latitude soils and weather pattern variability, the implementation of such coupled liquid and vapor phase numerical simulation remain to be tested. We consider the nonisothermal solution of the vapor flux equation that accounts for the thermally driven water vapor transport and phase changes. Fully coupled flux model outputs are compared and contrasted against field measurements of soil temperature, heat flux, water content, and evaporation in a subarctic agroecosystem in Alaska. Two welldefined hydro-meteorological situations were selected: dry and wet periods. Numerical simulation was forced by time series of incoming global solar radiation and atmospheric surface layer thermodynamic parameters: surface wind speed, ambient temperature, relative humidity, precipitation, and soil temperature and soil moisture. In this simulation, soil parameters changing in depth and time are considered as dynamically adjusted boundary conditions for solving the set of coupled differential equations. Results from this evaluation give good correlation of modeled and observed data in ) during the dry period. On the other hand, a poor agreement was obtained in the radiative fluxes and turbulent fluxes during the wet period due to the lack of representation in the radiation field and differences in soil dynamics across the landscape.

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“…liquid water and water vapor (Cahill and Parlange, 1998;Hansson et al, 2004;Jones and Moberg, 2003;Lundin, 1985;Saito et al, 2006):…”

Section: Model Descriptionmentioning

confidence: 99%

“…The flux densities of liquid water (q L ) and water vapor (q v ) are defined as (Cahill and Parlange, 1998;Saito et al, 2006):…”

Section: Model Descriptionmentioning

confidence: 99%

“…However, heat conduction is not the only mechanism for heat transport in soils and ecosystems. Cahill and Parlange (1998) indicated that liquid water and thermally-induced vapor movement (convection) contributed to~50% of soil heat flux in temperate soils. In boreal soils where moisture is highly variable across space and through seasons, the role of water movement could be an important factor in seasonal soil energy dynamics and in the long term response of boreal systems to changes in climate.…”

Section: Introductionmentioning

confidence: 99%

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