Diurnal variations in vegetation activity affecting shallow groundwater flow identified by microthermal measurements

Observations of summer microthermal temperature variations suggest, next to hydrological factors, a significant influence of plant activity on groundwater flow in fractured claystone materials. Variations in groundwater microtemperature were compared to variations in meteorological parameters and electrical potential of plants. With an increase in surface temperature, relative air humidity decreases and an increase in tree electrical potential, measured as the difference between the northern and the southern stem exposure (N–S), can be observed. This increase in electrical potential is concomitant with a change in groundwater temperature of approximately 2 mK. This relationship does not always occur. At high temperatures (+30° C) the decrease amounts to just 1 mK. This fact is related to the change in transpiration of plants, decreased or even suspended at high surface temperatures. A frequency analysis of all data showed a daily frequency of high magnitude in all parameters. Possibly changes in the macro weather situation events were observed in the results of atmospheric pressure, southern electric potential and groundwater temperature. The lag time between changes in electric potential and subsurface microtemperature changes amounts to 17 hours, possibly a result of the electrical potential difference between the northern and the southern exposure of the stem (N–S), and 5 hours, the result of the change in electrical potential difference between the southern and the northern stem exposure side (S–N). A comparison between potential changes and the computed change in gravity resulting from earth tidal effects showed that the correlation between the subsurface temperature variation with up to 2 mK and the change in surface temperature variation does not match directly. Other study shows that the impact of earth tides on subsurface microtemperature variation amounts to ca. 1mK. The effect of groundwater abstraction by mature vegetation is determined at the same range. Atmospheric tides can be correlated with the changes in north and south electric potentials

Compressible primitive equation: formal derivation and stability of weak solutions

We present a formal derivation of a simplified version of Compressible Primitive Equations (CPEs) for atmosphere modeling. They are obtained from $3$-D compressible Navier-Stokes equations with an \emph{anisotropic viscous stress tensor} where viscosity depends on the density. We then study the stability of the weak solutions of this model by using an intermediate model, called model problem, which is more simple and practical, to achieve the main result

Exhumation of the central Wasatch Mountains, Utah: 2. Thermokinematic model of exhumation, erosion, and thermochronometer interpretation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95279/1/jgrb13381.pd

Thermal properties of sand and mineral flours

The determination of the thermal conductivity and the thermal diffusivity of granular dry material is exposed to the problem of heat transfer between the heat source of an instrument and the media of investigation. This problem can be solved by filling the pore space with various fluids. An empirical relation between the thermal conductivity and the diffusivity of the composed media and the thermal conductivity of the pore fluid is extrapolated to the value of air as a pore filling. A further method provides the heat contact conductance of the fluid–solid interface during a non-stationary state which allows the estimation of the thermal diffusivity for air in the pore space. The validity of the geometric mean, which is often used to estimate the thermal conductivity of composed media, is limited to a heat conductivity contrast of up to 1:20. The structural constant of Wiener’s mixing rule represents not only a fixed structure of the pore space, but also relates to the heat transfer properties at the fluid–solid interface. It strongly varies with the surface tension of the fluid as well as with its wetting property

Geothermics: an introduction

Includes bibliographical references and index

Daily temperature variations at the subsurface combined with water level records in Ajameti, Georgia

High resolution temperatures at the subsurface down to 250 m and water level measurements were carried out in a borehole at Ajameti, Georgia. In both cases daily variations were analyzed for time periods of February/March 2018 and April 2018. Their frequency spectra demonstrate that the diurnal and semi-diurnal variations are generated by earth tides. The enhanced amplitude of the diurnal period at depth of 100 m coincides with the growth phase of vegetation. Frequent rainfall did not affect the temperature at 100 m or deeper but raises the water level. Daily surface temperature variations relate to the temperature variation at the subsurface during the growth phase of vegetation in April and down to 175 m. No relation is detected in records obtained during February/March and at 250 m in both cases. Vertical shift of the water column results from the prevailing temperature gradient and the temperature fluctuation. The estimated water flow yields an amplitude of 0.1 m at 250 m but increases continuously to 0.16 m at 100 m. However, the water level variation reaches only 0.03 m at the surface. It is likely that the free surface of the water level has an additional degree of freedom which causes the lower magnitude of fluctuation

Applying temperature and pressure measurements For estimating the size of a water reservoir

Beside geological methods for determination of the size of a water reservoir, temperature and pressure records in boreholes are used as complementary means. They can be applied, if several wells are available. If a hydraulic connection exists between two given wells, a variation in one well can also be monitored in the second one. On the other hand, a displacement of an aquifer can be found, if a change in one borehole does not affect the temperature or water level in another borehole. The water reservoirs in and near to Tbilisi are separated aquifers for which the hydraulic connection exists between the wells in every reservoir. Additionally, strong pressure changes in the more distant Samgori oil reservoir affect also the hydrothermal field of the central thermal water reservoir at Tbilisi