The role of soil hydro-physical properties in the atmospheric water cycle

<p>Soil hydro-physical properties are necessary components in regional climate simulation; yet, the parameter inaccuracies introduce uncertainty in the representation of surface water and energy fluxes leading to differences in land-atmosphere interactions, and precipitation. This study examines the uncertainties in the North American atmospheric water cycle that result from the use of different soil datasets. Two soil datasets are considered: STATSGO from the United States Department of Agriculture and GSDE from Beijing Normal University.  Each dataset's dominant soil category allocations differ significantly at the model's resolution. Large regional discrepancies are found in the assignments of soil category, such that, for instance, in the Midwestern US (hereafter, Midwest), there is a systematic reduction in soil grain size allowing the impacts of the differing assignments to project onto regional scales.</p> <p>The two simulations are conducted from June 1–August 31, 2016–2018 using the Weather Research and Forecasting Model coupled with the Community Land Model version 4. In the Midwest, where soil grain size decreases from STATSGO to GSDE, the GSDE simulation experiences reduced mean latent heat flux (–15 W m<sup>-2</sup>), and increased sensible heat flux (+15 W m<sup>-2</sup>).  The boundary layer thermodynamic structure responds to these changes resulting in differences in mean CAPE and CIN. In the GSDE simulation, there is more energy available for convection (CAPE: +200 J kg<sup>-1</sup>) in the Midwest, but it is more difficult to access that energy (CIN: +75 J kg<sup>-1</sup>). Differences arise in dynamic quantities, as well: the vertically-integrated moisture fluxes suggest a reduction in continental cyclonic rotation co-located with the decrease in latent heat flux and, the vertically-integrated moisture flux convergence is also affected. This combination of thermodynamic and dynamic responses culminate in a reduction of precipitation in the Midwest, which can be related to changes in the placement of soil hydro-physical properties.</p>

Variation in grain-size characteristics of simulated shrubs as a novel sand-barrier in a wind tunnel experiment

Sand transport is the main manifestation of sand damage in the arid and semiarid regions globally. It is a huge challenge to stabilize mobile sandy and change them into stable productive ecosystems. The establishment of simulated shrubs is one of the most effective measures to solve the above difficulties as a novel sand-barrier. To clarify simulated shrubs’ role in the process of ecological restoration. It will be greatly helpful to incorporate the shelter device proposed in the present work into landscape models for aeolian soil transport, to optimize the parameters associated with the sand-barrier characteristics for aeolian soil stabilization at the field scale. A series of wind tunnel experiments were conducted to analyze the variations of soil grain-size of simulated shrubs with different spatial configurations, row spaces, and net wind speeds. Further, the soil grain-size parameters were calculated by the classic method proposed by Folk and Ward to clarify the change of soil particles resulted from the blocking effects. The average grain-size content of simulated shrubs with different spatial configurations, row spaces, and net wind speeds was dominated by medium sand and fine sand, and the total percentage was more than 90%. Moreover, the sand deposition of simulated shrubs with different spatial configurations increased with the improvement of wind speeds. The average sand deposition of spindle-shaped simulated shrubs in 17.5 × 17.5 cm and broom-shaped simulated shrubs in 17.5 × 26.25 cm under different net wind speeds was the least. The effects of row spaces on average grain-size parameters increased with the improvement of net wind speeds. By calculating the correct characteristics of specific shelter devices proposed in the present work, all of these findings suggest that the application of simulated shrubs will be an important component to further extend ecological engineering projects in arid and semiarid regions.

The role of soil hydrophysical properties in the atmospheric water cycle

<p>Soil hydrophysical properties are necessary components in weather and climate simulation; yet, the parameter inaccuracies may introduce considerable uncertainty in the representation of surface water and energy fluxes. The surface fluxes not only affect the terrestrial water and energy budgets, but through land-atmosphere interactions, they can influence the boundary layer, atmospheric stability, moisture transports, and regional precipitation characteristics. This study uses seasonal coupled simulations to examine the uncertainties in the North American atmospheric water cycle that result from the use of different soil datasets. Two soil datasets are considered: State Soil Geographic dataset (STATSGO) from the United States Department of Agriculture and Global Soil Dataset for Earth System Modeling (GSDE) from Beijing Normal University.  Each dataset's dominant soil category allocations differ significantly at the model's resolution (15 km). It is found that large coherent regional discrepancies exist in the assignments of soil category, such that, for instance, in the Midwestern United States (hereafter, Midwest), there is a systematic reduction in soil grain size. Because the soil grain size is regionally biased, it allows for analysis of the impact of soil hydrophysical properties projected onto regional scales.</p><p>The two simulations are conducted from June 1–August 31, 2016–2018 using the Weather Research and Forecasting Model (WRF) coupled with the Community Land Model (CLM) version 4. It is found that in the Midwest, where the soil grain size decreases from STATSGO to GSDE, the GSDE simulation experiences reduced mean latent heat flux (–15 W m<sup>-2</sup>), and increased sensible heat flux (+15 W m<sup>-2</sup>).  The differences in fluxes lead to differences in low-level specific humidity and 2-m temperature. The boundary layer thermodynamic structure responds to these changes resulting in differences in mean CAPE and CIN. In the GSDE simulation, there is more energy available for convection (CAPE: +200 J kg<sup>-1</sup>) in the Midwest, but it is more difficult to access that energy (CIN: +75 J kg<sup>-1</sup>). Furthermore, a reduction in low-level moisture generates a similar reduction in column-integrated moisture (i.e., precipitable water), resulting in conditions that are less conducive for precipitation.</p><p>Interestingly, the soil-texture-related surface fluxes are not confined to thermodynamic influence, but their influence extends to dynamic fields as well. Differences in the vertically-integrated wind field suggest a weakening of the continental low-pressure system (i.e., denoted by a reduction in cyclonic rotation) co-located with the decrease in latent heat flux in the Midwest. The associated vertically-integrated moisture fluxes mirror the dissimilarities in the wind fields. Consequently, the moisture fluxes yield differences in vertically-integrated moisture flux convergence in the same region, as well. This combination of thermodynamic and dynamic variable differences culminates in a reduction of average precipitation in the Midwest, which can be related to changes in the placement of soil hydrophysical properties via soil texture. Through land-atmosphere interactions, it is shown that soil parameters can affect each component of the atmospheric water budget.</p>

Variation in Grain-size Characteristics of Stimulated Shrubs As a Novel Sand-barrier in a Wind Tunnel Experiment

<p>Sand transport is the main manifestation of sand damage in the arid and semiarid desert regions globally. It is still a challenge for ecologists to stabilize mobile sandy and to change them into stable productive ecosystems. The establishment of stimulated shrubs is one of the most effective measures as a novel sand-barrier. Meanwhile, it has a beautiful visual effect in deserts. To better understand its role in the process of ecological restoration, we conducted a wind tunnel experiment to analyze the overall characteristics of soil grain-size variation of different spatial configurations with simulated shrubs in row spaces under different net wind speeds. The results present that the average grain-size content was dominated by medium sand and fine sand, and the total percentage was more than 90%. The average grain-size content for other soil grain-size was almost the same and the proportion was less than 10%. Moreover, the sand deposition of simulated shrubs with different spatial configurations increased with the improvement of wind speed. And the average sand deposition of spindle-shaped simulated shrubs in 17.5×17.5cm and broom-shaped simulated shrubs in 17.5×26.25cm under different wind speeds was the least. There was less variation of the soil grain-size parameters among different spatial configurations of stimulated shrubs, row spaces, and net wind speeds. The effects of row spaces on average grain-size parameters would be improved with the increase of wind speed. By calculating the “correct” characteristics of any specific shelter device, all of these findings suggest that the application of the simulated shrubs will be an important component to further extend ecological engineering projects in arid and semiarid desert regions.</p>

ПОЧВООБРАЗУЮЩЕЕ ЗНАЧЕНИЕ ВЫНОСЯЩЕЙ (ПЕРЕОТЛОЖНОЙ) ДЕЯТЕЛЬНОСТИ КРОТА ЕВРОПЕЙСКОГО (TALPA EUROPAEA, L) В ТАЕЖНОМ БИОГЕОЦЕНОЗЕ

The soil discharges made by moles (molehills) consist of mixed superficial soil layers where the main physicochemical parameters of soil show beneficial changes, including reduced density, moisture and acidity and increased humus content, especially during the first three months after molehill formation. In the present study, the biocenoses most preferred by the European mole (Talpa europaea, L) in Vologda Region have been determined. Most avidly inhabited by moles were moistened areas at forest edges and mixed young growths on glades. A limiting factor of the excavating activity of moles is soil grain-size composition. Moles prefer light and middle- density loams where its activity is high than in areas with light sandy loams and heavy loams. Data on the areas modified by moles in different sylvan biocenoses have been obtained. A positive effect of mole activities is facilitating the beneficial conditions for the restoration of plant communities destroyed by deforestation.

THE EFFECT OF SOIL GRAIN SIZE ON THE DEFORMATION PROPERTIES OF REINFORCED GEOCELL LAYERS

The effect of backfill material grading on the behaviour of geocell reinforced layers was experimentally investigated in this study. A series of loading tests were performed on a model with geocell reinforced and unreinforced layers. Five types of crushed aggregates were used as backfill materials in the experiment. The results showed that geocell reinforcement increased the deformation parameters. The rate of increase of the deformation characteristics depended on the backfill material grading.