Monthly Drought Index (1951-2016) and 8-day Frequency Soil Moisture (2007-2016) Dataset in Southwest China
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Abstract Taking weak expansive soil as the research object, octadecyl primary amine (octadecylamine) was mixed into remolded expansive soil as a water repellent, and modified samples with different octadecylamine content and initial moisture content were configured. The dripping water penetration time method was used to determine the water repellency grade of the modified expansive soil, and the critical moisture content test of the modified expansive soil was carried out to analyze the relationship between different octadecylamine content and the initial moisture content of the expansive soil. The results show that with the increase of the initial moisture content, the water repellency of the modified expansive soil first increases and then decreases. When the octadecylamine content is 0.8%, the limit moisture content is 33.33%, and the peak moisture content is 29.51%. The bottom water content is 0%, and its interval value is 3.78 times larger than when the octadecylamine content is 0.2%.he above research results can provide a test basis for the engineering application of modified expansive soils.
Expansive clay
Expansive
Atterberg limits
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Neutron instrument is a high-tech,intelligent and advanced instrument,it is extensively used in measuring soil moisture content without disturbing soil in fieldwork,can be easily operated to successively monitor soil moisture content at any depths at the same measuring site,the measurement does not be limited by seasons,change of physical and chemical properties of soils,and can be connected with automatically recording system and computer.Neutron instrument is extensively used in many domains,such as pedology,geography,agriculture,forestry,meteorology,hydrogeology,and water conservancy and building projects.In this paper,the calibrating equation of soil moisture content measured with neutron instrument is developed,and the methods for increasing the measuring precision of shallow soil moisture content are researched,compared and verified. The traditional dying method is regarded as the criterion in measuring soil moisture content.The test results are calibrated and verified in field.The result shows that the hierarchical-section method is optimal in calibrating shallow soil moisture,and the relative errors are lower than 10%,which can satisfy the requirements of measuring shallow soil moisture content;the measuring precision of shallow soil moisture content can not be increased by the indirect derivation using deep soil moisture content;the results of shallow soil moisture content calibrated with the regressed equation of nonlinear least square method are not stable,and the test errors are high.Generally,it is considered that the detecting radius of neutron instrument is related to soil properties and moisture content.
Neutron probe
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Water activity
Content (measure theory)
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Abstract This study evaluates the intraseasonal variation of winter precipitation over the western United States in 14 coupled general circulation models (GCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Eight years of each model’s twentieth-century climate simulation are analyzed. The focus is on the two dominant intraseasonal modes for the western U.S. precipitation: the 40-day mode and the 22-day mode. The results show that the models tend to overestimate the northern winter (November–April) seasonal mean precipitation over the western United States and Canada. The models also tend to produce overly strong intraseasonal variability in western U.S. wintertime precipitation, in spite of the overly weak tropical intraseasonal variability in most of the models. All models capture both the 40-day mode and the 22-day mode, usually with overly large variances. For the 40-day mode, models tend to reproduce its deep barotropic vertical structure and three-cell horizontal structure, but only 5 of the 14 models capture its northward propagation, and only 2 models simulate its teleconnection with the Madden–Julian oscillation in the tropical Pacific. For the 22-day mode, 8 of the 14 models reproduce its coherent northward propagation, and 9 models capture its teleconnection with precipitation in the tropical Pacific.
Teleconnection
Barotropic fluid
Mode (computer interface)
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<p>Research on moisture content distribution in the root zone is intended to determine the moisture content in accordance with tea plant and its distribution pattern. Measurement of moisture content by using gypsum block as media liaison between the soil and water in the soil moisture is conducted by means Bouyoucos Soil Meter. Moisture content is obtained by performing measurements on a laboratory and field scale. Laboratory scale test is emphasized on calibration of the gypsum block to be applied in the measurement field. Site measurement was made in three drill holes, each 150 cm in depth, which are at peak, slopes and valleys in the study area that had been predetermined. The result of research shown that high moisture content about 50% –95% which tends to increase downward modeling on moisture content has similar result to the \ field measurement. Tea plants needed of relative large moisture content, since it requires a moisture content continuosly and yields of tea leave.</p>
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The one-dimensional steady hygrothermal field in a porous infinite strip subjected to severe hygrothermal gap on its surfaces considering nonlinear coupling between heat and moisture is analyzed. Heat and moisture aie considered to diffuse macroscopically. Moreover, moisture is considered to take two phases, namely, dissolved and gaseous phases. Both types of moisture are considered to have different diffusivities. To consider the coupling between heat and moisture, the heat generation by transformation from gaseous moisture into dissolved one is considered as well as the transformation from dissolved moisture into gaseous one due to temperature change. The balance between dissolved and gaseous moisture is determined by an equilibrium condition. The effects of the coupling properties and the difference between the diffusivities of moisture on the distributions of heat and moisture are investigated.
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Information on the thermal properties of soils from different disciplines of science and engineering is consolidated to identify low‐cost, simple procedures for assessing the variation of the thermal resistivity of soils with changes in moisture content. Three procedures for determining the critical moisture content are presented. The critical moisture content is the moisture content at the knee of the Thermal‐resistivity‐versus‐moisture‐content curve. The optimum moisture content and plastic limit were found to be physical quan tities indicative of the critical moisture content in soils. Also, the upper flex point of the soil‐moisture‐characteristics curve appears to establish the critical moisture content in soils.
Atterberg limits
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Abstract The unfrozen water content in an unsaturated frozen light clay soil having a range of initial soil moisture contents was measured independently using TDR and NMR in order to investigate the relationship between the unfrozen water content within a frozen soil and the initial soil moisture content. Unfrozen water contents measured by TDR and NMR were highly correlated and it was evident that the amount of unfrozen water in contact with ice at a given temperature was in proportion to the initial soil moisture content significantly. Since the effect of solutes in soil on the osmotic potential was negligible, a plausible interpretation for the dependence of the unfrozen water content on the initial soil moisture content was assumed to be the matric potential of unfrozen water being affected by both soil particles and ice.
Water potential
Water retention curve
Clay soil
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