scholarly journals Implementation of salt-induced freezing point depression function into CoupModel_v5 for improvement of modelling seasonally frozen soils

2018 ◽  
Author(s):  
Mousong Wu ◽  
Per-Erik Jansson ◽  
Jingwei Wu ◽  
Xiao Tan ◽  
Kang Wang ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Soil Water ◽  
Field Experiments ◽  
Freezing Point ◽  
Numerical Models ◽  
Soil Freezing ◽  
Freezing Point Depression ◽  
Soil Hydrology ◽  
Cold Regions ◽  
New Model

Abstract. Soil freezing/thawing is important for soil hydrology and water management in cold regions. Salt in agricultural field impacts soil freezing/thawing characteristics and therefore soil hydrologic process. In this context, we conducted field experiments on soil water, heat and salt dynamics in two seasonally frozen agricultural regions of northern China to understand influences of salt on cold regions hydrology. We developed CoupModel by implementing impacts of salt on freezing point depression. We employed a Monte-Carlo sampling method to calibrate the new model with field observations. The new model improved soil temperature mean error (ME) by 16 % to 77 % when new freezing point equations were implemented into CoupModel. Nevertheless, we found that parameters related to energy balance and soil freezing characteristics in the new model were sensitive to soil heat and water transport at both sites. However, a systematic model sensitivity and calibration has shown to be able to improve model performance, with mean values of R2 from behavioral simulations for soil temperature at 5 cm depth as high as 0.87 and 0.90, and mean value of R2 for simulated soil water (liquid or total water contents at 5 cm depth) of 0.31 and 0.80 at site Qianguo and site Yonglian, respectively. This study provided a new approach considering influences of salt on soil freezing/thawing in numerical models and highlighted the importance of salt in soil hydrology of seasonally frozen agricultural soils.

VARIATION OF SUNFLOWER GROWTH, SOIL MOISTURE AND SOIL TEMPERATURE IN RELATION TO PLANTING PATTERNS AT A HIGH LATITUDE SITE

2001 ◽  
Vol 49 (3) ◽  
pp. 273-282 ◽  
Author(s):  
M. Long ◽  
H. Eiszner
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Soil Water ◽  
High Latitude ◽  
Dry Matter ◽  
Field Experiments ◽  
Hyperbolic Model ◽  
Row Spacing ◽  
Dry Matter Accumulation ◽  
Deep Soil

HALLE-WITTENBERG, HALLE(SAALE), GERMANY Received: 13 June, 2001; accepted: 6 August, 2001 Field experiments were conducted at a high latitude site for sunflower (Helianthus annuus L.) production in central Germany (51 o 24' N, 11 o 53' E) in 1996, 1997 and 1998. The responses of sunflower development to various planting patterns differed in the duration from emergence to the middle of the linear growth period as calculated via a tangent hyperbolic model F(t)=(. +ß)×tanh[. ×(t–.)]. Final dry matter accumulation showed few differences among the planting patterns: 12 plants m –2 at 50 cm row spacing at 75 cm row spacing (RS2PD2) and 4 plants m –2 at 100 cm row spacing (RS3PD1). The actual and simulated values for final dry matter were close to 1200 g m –2 . The responses of soil moisture and temperature to planting patterns changed from the upper to the deep soil layers. In a normal year, e.g. 1997, the soil water to 150 cm depth was sufficient for sunflower growth. In a drought year, e.g. 1998, soil water deeper than 150 cm was used by sunflower crops. The soil temperature was mostly lower in RS1PD3 and RS2PD2 than in RS3PD1, particularly in the upper soil, at depths of 5 and 20 cm. The most important factor defining the responses of soil moisture and temperature to planting patterns seems to be the amount of radiation penetrating the ground, which may depend on latitude, wind and row orientation.

Process-based hydrological modeling: accounting for subsurface heterogeneity by integrating pedology, geophysics and soil hydrology

2020 ◽  
Author(s):  
Edoardo Martini ◽  
Ute Wollschläger ◽  
Marco Bittelli ◽  
Fausto Tomei ◽  
Ulrike Werban ◽  
...  
Keyword(s):  
Soil Water ◽  
Vadose Zone ◽  
Hydrological Modeling ◽  
Numerical Models ◽  
Spatial Scales ◽  
Three Dimensions ◽  
Water Fluxes ◽  
Soil Hydrology ◽  
Subsurface Heterogeneity ◽  
Highly Nonlinear

<p>As most hydrological processes are highly nonlinear and controlled by time-varying boundary conditions, numerical models are required for their comprehensive representation. However, one of the major difficulties in vadose zone processes modeling is due to the fact that soils are heterogeneous at all spatial scales. The identification and accurate representation of such heterogeneity can be crucial for quantifying the subsurface hydrological states and water fluxes but it is still a challenge in soil hydrology.</p><p>We present an integrated approach for process-based modeling of the vadose zone for a typical hillslope. The approach builds on the integration of classical soil mapping, on accurate monitoring of soil water content as well as on geophysical measurements for characterizing the subsurface heterogeneity. It finally integrates the gathered information into a physical model for simulating the vadose-zone processes with high spatial and temporal resolution.</p><p>Starting with a simple soil representation, we present the modeling results for different scenarios of increasing complexity with focus on the discretization and corresponding hydrological parameterization of the soil structures in three dimensions. We highlight and discuss the key challenges that need to be addressed when continuous information about the subsurface heterogeneity is to be mapped in the field and represented in a numerical model.</p><p>We argue that linking state-of-the-art experimental methods to advanced numerical tools, and bridging the gap between different disciplines such as pedology, hydrology and geophysics can be the key for improving our ability to measure, predict and better understand the vadose-zone processes. This will provide important knowledge needed for transferring this approach to larger scales where the accurate quantification of the soil water fluxes is required for a more efficient water management in the context of sustainable food production and climate change.</p>

Measurement of the suction of soil water by Portland stone absorbers calibrated by a new method for determining vapour pressures near to saturation

1942 ◽  
Vol 32 (4) ◽  
pp. 413-427 ◽  
Author(s):  
A. L. C. Davidson ◽  
R. K. Schofield
Keyword(s):  
Soil Water ◽  
Vapour Pressure ◽  
Freezing Point ◽  
Salt Content ◽  
Thin Plates ◽  
Freezing Point Depression ◽  
Low Salt ◽  
Dissolved Matter ◽  
Correct Reading ◽  
A New Technique

1. A filter apparatus cannot be relied upon to give a correct reading of the suction of soil water when this exceeds about 400 cm. of water.2. Owing to the contribution of dissolved matter to the freezing-point depression the suction in a soil of normal low salt content can only be obtained from the freezing-point depression with reasonable accuracy when it exceeds about 4000 cm. of water (freezing-point depression greater than 0–3° C).3. Suctions in the range 400 to 4000 cm. have been measured with the aid of calibrated absorbers consisting of thin plates of Portland stone.4. The plates were calibrated up to 1000 cm. by the application of suction through a filter, and above 1000 cm. by measuring the vapour-pressure depression by a new technique.5. When applied direct to soil, the new vapour-pressure technique is more reliable than the freezing-point method, and can be applied to materials which do not exhibit a well-defined freezing-point.6. A suitable soil was washed free from salts and brought to 1000 cm. suction on a filter. Measurements of the vapour-pressure depression and the freezing-point depression checked well with the thermodynamic formulae.

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