A study of the sensitivity of bare soil evaporation schemes to soil surface wetness, using the coupled soil moisture and surface temperature prediction model, BARESOIL

1995 ◽  
Vol 55 (1-2) ◽  
pp. 101-112 ◽  
Author(s):  
Lj. Dekić ◽  
D. T. Mihailović ◽  
B. Rajković
Keyword(s):  
Soil Moisture ◽  
Prediction Model ◽  
Surface Temperature ◽  
Soil Surface ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Temperature Prediction ◽  
Surface Wetness ◽  
Bare Soil Evaporation

scholarly journals Testing water fluxes and storage from two hydrology configurations within the ORCHIDEE land surface model across US semi-arid sites

2020 ◽  
Vol 24 (11) ◽  
pp. 5203-5230
Author(s):  
Natasha MacBean ◽  
Russell L. Scott ◽  
Joel A. Biederman ◽  
Catherine Ottlé ◽  
Nicolas Vuichard ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Moisture Diffusion ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Arid Ecosystems ◽  
Layer Model ◽  
Soil Fraction ◽  
Bare Soil Evaporation ◽  
Semi Arid

Abstract. Plant activity in semi-arid ecosystems is largely controlled by pulses of precipitation, making them particularly vulnerable to increased aridity that is expected with climate change. Simple bucket-model hydrology schemes in land surface models (LSMs) have had limited ability in accurately capturing semi-arid water stores and fluxes. Recent, more complex, LSM hydrology models have not been widely evaluated against semi-arid ecosystem in situ data. We hypothesize that the failure of older LSM versions to represent evapotranspiration, ET, in arid lands is because simple bucket models do not capture realistic fluctuations in upper-layer soil moisture. We therefore predict that including a discretized soil hydrology scheme based on a mechanistic description of moisture diffusion will result in an improvement in model ET when compared to data because the temporal variability of upper-layer soil moisture content better corresponds to that of precipitation inputs. To test this prediction, we compared ORCHIDEE LSM simulations from (1) a simple conceptual 2-layer bucket scheme with fixed hydraulic parameters and (2) an 11-layer discretized mechanistic scheme of moisture diffusion in unsaturated soil based on Richards equations, against daily and monthly soil moisture and ET observations, together with data-derived estimates of transpiration / evapotranspiration, T∕ET, ratios, from six semi-arid grass, shrub, and forest sites in the south-western USA. The 11-layer scheme also has modified calculations of surface runoff, water limitation, and resistance to bare soil evaporation, E, to be compatible with the more complex hydrology configuration. To diagnose remaining discrepancies in the 11-layer model, we tested two further configurations: (i) the addition of a term that captures bare soil evaporation resistance to dry soil; and (ii) reduced bare soil fractional vegetation cover. We found that the more mechanistic 11-layer model results in a better representation of the daily and monthly ET observations. We show that, as predicted, this is because of improved simulation of soil moisture in the upper layers of soil (top ∼ 10 cm). Some discrepancies between observed and modelled soil moisture and ET may allow us to prioritize future model development and the collection of additional data. Biases in winter and spring soil moisture at the forest sites could be explained by inaccurate soil moisture data during periods of soil freezing and/or underestimated snow forcing data. Although ET is generally well captured by the 11-layer model, modelled T∕ET ratios were generally lower than estimated values across all sites, particularly during the monsoon season. Adding a soil resistance term generally decreased simulated bare soil evaporation, E, and increased soil moisture content, thus increasing transpiration, T, and reducing the negative bias between modelled and estimated monsoon T∕ET ratios. This negative bias could also be accounted for at the low-elevation sites by decreasing the model bare soil fraction, thus increasing the amount of transpiring leaf area. However, adding the bare soil resistance term and decreasing the bare soil fraction both degraded the model fit to ET observations. Furthermore, remaining discrepancies in the timing of the transition from minimum T∕ET ratios during the hot, dry May–June period to high values at the start of the monsoon in July–August may also point towards incorrect modelling of leaf phenology and vegetation growth in response to monsoon rains. We conclude that a discretized soil hydrology scheme and associated developments improve estimates of ET by allowing the modelled upper-layer soil moisture to more closely match the pulse precipitation dynamics of these semi-arid ecosystems; however, the partitioning of T from E is not solved by this modification alone.

Remote detection of bare soil moisture using a surface-temperature-based soil evaporation transfer coefficient

2010 ◽  
Vol 12 (5) ◽  
pp. 351-358 ◽  
Author(s):  
Shaohua Zhao ◽  
Yonghui Yang ◽  
Guoyu Qiu ◽  
Qiming Qin ◽  
Yunjun Yao ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Remote Detection

A Coupled Soil Moisture and Surface Temperature Prediction Model

1991 ◽  
Vol 30 (6) ◽  
pp. 812-822 ◽  
Author(s):  
F. Ács ◽  
D. T. Mihailović ◽  
B. Rajković
Keyword(s):  
Soil Moisture ◽  
Prediction Model ◽  
Surface Temperature ◽  
Temperature Prediction

scholarly journals Multi-variable, multi-configuration testing of ORCHIDEE land surface model water flux and storage estimates across semi-arid sites in the southwestern US

2019 ◽  
Author(s):  
Natasha MacBean ◽  
Russell L. Scott ◽  
Joel A. Biederman ◽  
Catherine Ottlé ◽  
Nicolas Vuichard ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Moisture Diffusion ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Arid Ecosystems ◽  
Soil Hydrology ◽  
Soil Fraction ◽  
Bare Soil Evaporation ◽  
Semi Arid

Abstract. Plant activity in semi-arid ecosystems is largely controlled by pulses of precipitation, making them particularly vulnerable to increased aridity expected with climate change. Simple bucket-model hydrology schemes in land surface models (LSMs) have had limited ability in accurately capturing semi-arid water stores and fluxes. Recent, more complex, LSM hydrology models have not been widely evaluated against semi-arid ecosystem in situ data. We hypothesize that the failure of older LSM versions to represent evapotranspiration, ET, in arid lands is because simple bucket models do not capture realistic fluctuations in upper layer soil moisture. We therefore predict that including a discretized soil hydrology scheme based on a mechanistic description of moisture diffusion will result in an improvement in model ET when compared to data because the temporal variability of upper layer soil moisture content better corresponds to that of precipitation inputs. To test this prediction, we compared ORCHIDEE LSM simulations from (1) a simple conceptual 2-layer bucket scheme with fixed hydrological parameters; and (2) a 11-layer discretized mechanistic scheme of moisture diffusion in unsaturated soil based on Richards equations against daily and monthly soil moisture and ET observations, together with data-derived transpiration / evaporation, T / ET, ratios, from six semi-arid grass, shrub and forest sites in the southwestern USA. The 11-layer scheme also has modified calculations of surface runoff, bare soil evaporation, and water limitation to be compatible with the more complex hydrology configuration. To diagnose remaining discrepancies in the 11-layer model, we tested two further configurations: (i) the addition of a term that captures bare soil evaporation resistance to dry soil; and (ii) reduced bare soil fraction. We found that the more mechanistic 11-layer model results better representation of the daily and monthly ET observations. We show that is likely because of improved simulation of soil moisture in the upper layers of soil (top 5 cm). Some discrepancies between observed and modelled soil moisture and ET may allow us to prioritize future model development. Adding a soil resistance term generally decreased simulated E and increased soil moisture content, thus increasing T and T / ET ratios and reducing the negative T / ET model-data bias. By reducing the bare soil fraction in the model, we illustrated that modelled leaf T is too low at sparsely vegetated sites. We conclude that a discretized soil hydrology scheme and associated developments improves estimates of ET by allowing the model to more closely match the pulse precipitation dynamics of these semi-arid ecosystems; however, the partitioning of T from bare soil evaporation is not solved by this modification alone.

scholarly journals Improving the Processes in the Land Surface Scheme TERRA: Bare Soil Evaporation and Skin Temperature

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 513 ◽  
Author(s):  
Jan-Peter Schulz ◽  
Gerd Vogel
Keyword(s):  
Surface Temperature ◽  
Skin Temperature ◽  
Diurnal Cycle ◽  
Land Surface ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Diurnal Cycles ◽  
Bare Soil Evaporation ◽  
Dry Conditions ◽  
Surface Scheme

Newly improved formulations of the bare soil evaporation and the surface temperature are presented, using the multilayer land surface scheme TERRA of the Consortium for Small-scale Modeling (COSMO) atmospheric model. The simulations were carried out in offline mode with atmospheric forcing data from the Meteorological Observatory Lindenberg–Richard-Aßmann-Observatory of the German Meteorological Service. The results show that the bare soil evaporation simulated by the reference version of TERRA is substantially overestimated under wet conditions, and underestimated under dry conditions. Furthermore, the amplitude of the diurnal cycle of the surface temperature is systematically underestimated. In contrast, the diurnal cycles of the temperatures in the soil are overestimated instead. The new description of the bare soil evaporation in TERRA is based on a resistance formulation analogue to Ohm’s law, while the surface temperature is now based on the skin temperature formulation by Viterbo and Beljaars. The new formulation improves the simulated bare soil evaporation substantially. In particular, the overestimation under wet conditions is reduced, also acting against an extensive drying of the soil during the annual cycle. Additionally, the underestimation under dry conditions is reduced as well. Furthermore, the simulated amplitude of the diurnal cycle of the surface temperature is substantially increased. In particular, a nocturnal warm bias is systematically reduced. In addition to this, the new formulations were also applied in coupled mode in the COSMO model, resulting in improved diurnal cycles of near-surface temperature and dew point.

Observations and modeling of evapotranspiration and dewfall during the 2018 meteorological drought in southern England

2020 ◽  
Author(s):  
Simon R. Osborne ◽  
Graham P. Weedon
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Meteorological Drought ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Rooting Depth ◽  
Bare Soil Evaporation ◽  
Skin Temperatures

AbstractA meteorological drought in 2018 led to senescence of the C3 grass at Cardington, Bedfordshire, UK. Observations of near-surface atmospheric variables and soil moisture are compared to simulations by the JULES land surface model (LSM) as used for Met Office forecasts. In years without drought, JULES provides better standalone simulations of evapotranspiration (ET) and soil moisture when the canopy height and rooting depth are reduced to match local conditions. During drought with the adjusted configuration, JULES correctly estimates total ET, but the components are in the wrong proportions. Several factors affect the estimation of ET including modeled skin temperatures, dewfall and bare-soil evaporation. A diurnal range of skin temperatures close to observed is produced via the adjusted configuration and doubling the optical extinction coefficient. Although modeled ET during drought matches observed ET, this includes simulation of transpiration but in reality the grass was senescent. Excluding transpiration, the modeled bare-soil evaporation underestimates the observed midday latent heat flux. Part of the missing latent heat may relate to inappropriate parameterization of hydraulic properties of dry soils and part may be due to insufficient evaporation of dew. Dew meters indicate dewfall of up to 20 W m−2 during drought when the surface is cooling radiatively and turbulence is minimal. These data demonstrate that eddy-covariance techniques fail to reliably record the times, intensity and variations in negative latent heat flux. Furthermore, the parameterization of atmospheric turbulence as used in LSMs fails to represent accurately dewfall during calm conditions when the surface is radiatively cooled.

Using soil surface temperature to assess soil evaporation in a drip irrigated vineyard

2013 ◽  
Vol 116 ◽  
pp. 128-141 ◽  
Author(s):  
B.L. Kerridge ◽  
J.W. Hornbuckle ◽  
E.W. Christen ◽  
R.D. Faulkner
Keyword(s):  
Surface Temperature ◽  
Soil Surface ◽  
Soil Evaporation ◽  
Soil Surface Temperature
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