Retrieving Soil Physical Properties via Assimilating SMAP Brightness Temperature Observations in the Community Land Model

2021 ◽  
Author(s):  
Hong Zhao ◽  
Yijian Zeng ◽  
Xujun Han ◽  
Bob Su
Keyword(s):  
Soil Moisture ◽  
Physical Properties ◽  
Soil Properties ◽  
Water Retention ◽  
Soil Physical Properties ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Community Land Model

<p>Basic soil physical properties (i.e., soil texture and organic matter) and associated soil hydraulic properties (i.e., soil water retention curve and hydraulic conductivity) play an essential role in land surface models (LSMs) for estimating soil moisture. With the physical link between soil properties, LSMs and Radiative Transfer Models (RTMs), the soil physical properties can be retrieved, using a LSM coupled with a microwave L-band emission observation model in a data assimilation framework. To this purpose, this paper couples an enhanced physically-based discrete scattering-emission model with the Community Land Model 4.5 (CLM), to retreive soil physical properties using the Local Ensemble Transform Kalman Filter (LETKF) algorithm, assimilating Soil Moisture Active and Passive (SMAP) Level-1C (L1C) brightness temperature at H and V polarization ( and ) separately, assisted with in situ measurements at the Maqu site on the eastern Tibetan Plateau. Results show the improved estimate of soil properties at the topmost layer via assimilating SMAP ( H, V), as well as at profile using the retrieved top-layer soil properties and a prior depth ratio. The use of  and  shows varied sensitivities to retrievals of different soil compositions (i.e., sand, clay, silt) and soil moisture estimates. However, analyses show that the retrieved soil properties with fine accuracy are not sensitive factors affecting soil moisture estimates. Instead, uncertainties of CLM model structures shall be considered, such as the fixed PTFs (pedotransfer functions), the hydraulic function describing soil water retention curve and the water stress function determining root water update.</p>

Relating soil structure and hydrophysical characteristics to aerobic and anaerobic soil respiration

2020 ◽  
Author(s):  
Teamrat Ghezzehei ◽  
Jennifer Alvarez ◽  
Yocelyn Villa ◽  
Rebecca Ryals
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Soil Water ◽  
Soil Structure ◽  
Water Retention ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Aerobic And Anaerobic

<p>The dynamics of soil organic matter is strongly controlled by the hydrophysical environmental factors, including motility, aqueous diffusivity of substrates, gaseous diffusivity, and energetic constraints on microbial physiology. The relationships among these physical factors depend on soil moisture and the architecture of the soil pores. In this regard, the soil water retention curve can serve as a macroscopic signature of pore-size distribution. Therefore, the sensitivity of aerobic and anaerobic microbial activity must be closely associated with the shape of the soil water retention curve. The soil water retention curve is, in turn, strongly dependent on soil texture and structure. Here, we present a physically-based model of aerobic and anaerobic microbial respiration rates. We also present a novel experimental technique for the characterization of the soil-moisture sensitivity of soil microbial activity. The proposed experimental and modeling approaches allow direct coupling of the fate soil organic matter with the nature of soil structure.</p>

scholarly journals Gamma-ray beam attenuation as an auxiliary technique for the evaluation of the soil water retention curve

1998 ◽  
Vol 55 (3) ◽  
pp. 498-502 ◽  
Author(s):  
O.O.S. BACCHI ◽  
K. REICHARDT ◽  
J.C.M. OLIVEIRA ◽  
D.R. NIELSEN
Keyword(s):  
Soil Moisture ◽  
Bulk Density ◽  
Water Retention ◽  
Gamma Ray ◽  
Soil Bulk Density ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Beam Attenuation

The soil water retention curve is fundamental for the hydraulic characterization of a soil and has many applications in agricultural research as well as in practical agriculture. A new procedure for soil moisture and soil bulk density evaluation inside closed pressure chambers through gamma-ray beam attenuation is presented. The proposed procedure presents several advantages in relation to the traditional process: avoids the need of continuous sample manipulation; minimizes the problem of hysteresis; allows a more precise evaluation of soil moisture by taking into account changes of soil bulk density due to swelling or shrinking on addition or removal of water; allows frequent evaluation of soil moisture without the need of opening the pressure chamber; allows a more precise judgement of equilibrium; reduces drastically the time of the determination of the retention curve and allows easy automation of data acquisition by a computer.

scholarly journals MINIMUM NUMBER OF POINTS FOR A RELIABLE SOIL WATER RETENTION CURVE USING RICHARDS’ PRESSURE CHAMBER

2020 ◽  
Vol 28 ◽  
pp. 477-487
Author(s):  
Gilmar Batista Grigolon ◽  
Adriano Valentim Diotto ◽  
Carlos José Gonçalves de Souza Lima ◽  
João Paulo Francisco ◽  
Marcos Vinícius Folegatti
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Water Retention ◽  
Soil Water Potential ◽  
Pressure Chamber ◽  
Water Dynamics ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve

The soil hydro-physical characteristics are very important for studies about soil water dynamics. The soil water retention curve it is a soil characteristic sometimes expensive and time consuming to be done and could be a problem for farmers. The numbers of points and its tension evaluated are normally choose arbitrarily. This study aimed to define the fewest pairs of soil moisture and water soil potential points which result in a reliable water retention curve in two different soils (sandy and clay). Using different tensions by suction table and Richards’ pressure chamber, nine replications were adjusted by van Genuchten's equation. Curves with 4, 5, 7, 8, 9, 10 and 13 points were studied and the curve with 13 points was adopted as standard. The obtained parameters for different pairs of soil moisture and their corresponding soil water potential were compared to the equivalent standard curve and submitted to analysis of variance (F test), and their values were compared by the Scott-Knott test (5% of probability). The curve with 7 points, using the tensions of 0; 40; 100; 300; 1,000; 5,000 e 15,000 hPa, was the lower number of points that did not showed statistical difference in any parameters of the model and the point with 15,000 hPa shown to be important and should be used on the combination of points to obtain a good adjustment.

Estimation of the water retention curve for unsaturated clay

2011 ◽  
Vol 91 (4) ◽  
pp. 543-549 ◽  
Author(s):  
Seid Majdeddin Mir Mohammad Hosseini ◽  
Navid Ganjian ◽  
Yadolah Pashang Pisheh
Keyword(s):  
Soil Properties ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Laboratory Tests ◽  
Water Retention ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Unsaturated Clay

Mir Mohammad Hosseini, S. M., Ganjian, N. and Pashang Pisheh, Y. 2011. Estimation of the water retention curve for unsaturated clay. Can. J. Soil Sci. 91: 543–549. Extensive laboratory tests are essential in order to determine the soil water retention curve, defined as the relationship between water content and suction, in an unsaturated soil. These laboratory tests are usually costly and time consuming. Moreover, for most practical problems, it has been found that approximate unsaturated soil properties are adequate for analysis. Thus, empirical procedures for predicting unsaturated soil parameters would be invaluable. The water retention curve can be estimated using soil properties to avoid the costs of experimental methods. Estimation of the water retention curve based on index properties is highly desirable due to its simplicity and low cost. Here, a model for the estimation of the soil water retention curve for fine soils is introduced, which takes the plasticity index and fine content into account, and is based on the Van Genuchten and Fredlund-Xing equations. The proposed equations are validated by comparing measured and simulated results. The curves predicted with these models were found to be in good agreement with the experimental results.

scholarly journals Pedotransfer functions for point and parametric estimations of soil water retention curve

2011 ◽  
Vol 52 (No, 7) ◽  
pp. 321-327 ◽  
Author(s):  
H. Merdun
Keyword(s):  
Soil Properties ◽  
Water Retention ◽  
Pedotransfer Functions ◽  
Water Retention Curve ◽  
Coefficient Of Determination ◽  
Retention Data ◽  
Parametric Methods ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve

A water retention curve is required for the simulation studies of water and solute transport in unsaturated or vadose zone. Unlike the direct measurement of water retention data, pedotransfer functions (PTFs) have attracted the attention of researchers for determining water retention curves from basic soil properties. The objective of this study was to develop and validate point and parametric PTFs for the estimation of water retention curve from basic soil properties such as particle-size distribution, bulk density, and porosity using multiple-linear regression technique and comparing the performances of point and two parametric methods using some evaluation criteria. 140 soil samples were collected from three different databases and divided as 100 and 40 for the derivation and validation of the PTFs. All three methods predicted water contents at selected water potentials and combined water retention curves pretty well, but van Genuchten&rsquo;s model performed the best in prediction. However, the differences among the methods in point and water retention curve predictions were not statistically significant (p &gt; 0.05). Prediction accuracies were evaluated by the coefficient of determination (R<sup>2</sup>) and the root mean square error (RMSE) between the measured and predicted values. The R<sup>2</sup> and RMSE were 0.962 and 0.036, 0.994 and 0.067, and 0.946 and 0.082 for point and parametric (van Genuchten, and Brooks and Corey) methods, respectively, in predicting combined water retention curve. The three methods can be alternatively used in the estimation of water retention curves, but parametric methods are preferred for yielding continuous water retention functions used in flow and transport modeling.

INFLUENCE OF SOIL MATRIX ON SOIL-WATER RETENTION CURVE AND HYDRAULIC CHARACTERISTICS

2017 ◽  
Vol 16 (4) ◽  
pp. 869-877
Author(s):  
Vasile Lucian Pavel ◽  
Florian Statescu ◽  
Dorin Cotiu.ca-Zauca ◽  
Gabriela Biali ◽  
Paula Cojocaru
Keyword(s):  
Soil Water ◽  
Water Retention ◽  
Water Retention Curve ◽  
Hydraulic Characteristics ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Soil Matrix ◽  
Retention Curve
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