Ground Temperature Measurements Research Articles

Thermal performance of heat drain under the road embankment near Hudson Strait Coast, Canada

Climate warming has affected the transportation infrastructure in Nunavik, Quebec, Canada. Heat drain is an innovative heat extraction technique using density-driven convection of the pore air in the geocomposite of the heat drain to cool the ground during winter. This paper examines the thermal conditions of the road embankment including a heat drain installed in the shoulder at Salluit, Nunavik, Quebec, Canada. Following the installation of the heat drain, a decrease of the soil temperatures was observed. A 2-D finite element geothermal model was developed to reproduce the thermal regime underneath the heat drain, based on the site condition at Salluit. Field measurement of ground temperature for the four year monitoring period from 2012 to 2016, were used to calibrate the model. After the calibration, the long-term climate warming effects on the ground thermal regime was investigated using the model developed.

Performance analysis of air-to-ground heat exchanger in equatorial Yaoundé: Hourly and daily thermal behaviour and efficiency optimization

This study examines an air-to-ground heat exchanger operating continuously during Yaoundé’s hottest month. The paper focuses on identifying cooling and heating periods based on the local thermal comfort range. We equally determine the duct length needed for 70 % efficiency at various air inlet speeds. Ground temperature measurements are taken to inform an analytical model predicting air outlet temperatures. Additionally, calculations are made for hourly thermal efficiency and potential. The results reveal ground temperatures ranging from 20.8 °C to 23.4 °C within 5 m of the surface. To achieve 70 % efficiency, duct lengths range from 44.3m to 48.7m depending on air inlet speed (0.5–1.5 m/s). The air-to-ground heat exchanger system can effectively cool buildings between 8am and 10pm, delivering comfortable air temperatures (23.5–25.5 °C). The air-to-ground heat exchanger can also provide heating from midnight to 5am before switching to cooling for the rest of the day. This demonstrates the potential of air-to-ground heat exchanger systems in equatorial climates to maintain comfortable indoor temperatures throughout the day by both heating and cooling buildings. The study's implications suggest that AGHEs can significantly enhance energy efficiency in building systems in equatorial regions, offering a sustainable solution for climate control. The novelty of this research lies in its detailed analysis of AGHE performance in a specific equatorial climate, addressing previously unexplored aspects of hourly and daily thermal behaviors, and providing valuable insights for optimizing AGHE systems in similar climates.

Robust Reconstruction of Historical Climate Change From Permafrost Boreholes

AbstractReconstructing historical climate change from deep ground temperature measurements in cold regions is often complicated by the presence of permafrost. Existing methods are typically unable to account for latent heat effects due to the freezing and thawing of the active layer. In this work, we propose a novel method for reconstructing historical ground surface temperature (GST) from borehole temperature measurements that accounts for seasonal thawing and refreezing of the active layer. Our method couples a recently developed fast numerical modeling scheme for two‐phase heat transport in permafrost soils with an ensemble‐based method for approximate Bayesian inference. We evaluate our method on two synthetic test cases covering both cold and warm permafrost conditions as well as using real data from a 100 m deep borehole on Sardakh Island in northeastern Siberia. Our analysis of the Sardakh Island borehole data confirms previous findings that GST in the region have likely risen by 5–9°C between the pre‐industrial period of 1750–1855 and 2012. We also show that latent heat effects due to seasonal freeze‐thaw have a substantial impact on the resulting reconstructed surface temperatures. We find that neglecting the thermal dynamics of the active layer can result in biases of roughly −1°C in cold conditions (i.e., mean annual ground temperature below −5°C) and as much as −2.6°C in warmer conditions where substantial active layer thickening (>200 cm) has occurred. Our results highlight the importance of considering seasonal freeze‐thaw in GST reconstructions from permafrost boreholes.

Post-fire stabilization of thaw-affected permafrost terrain in northern Alaska

In 2007, the Anaktuvuk River fire burned more than 1000 km2 of arctic tundra in northern Alaska, ~ 50% of which occurred in an area with ice-rich syngenetic permafrost (Yedoma). By 2014, widespread degradation of ice wedges was apparent in the Yedoma region. In a 50 km2 area, thaw subsidence was detected across 15% of the land area in repeat airborne LiDAR data acquired in 2009 and 2014. Updating observations with a 2021 airborne LiDAR dataset show that additional thaw subsidence was detected in < 1% of the study area, indicating stabilization of the thaw-affected permafrost terrain. Ground temperature measurements between 2010 and 2015 indicated that the number of near-surface soil thawing-degree-days at the burn site were 3 × greater than at an unburned control site, but by 2022 the number was reduced to 1.3 × greater. Mean annual ground temperature of the near-surface permafrost increased by 0.33 °C/yr in the burn site up to 7-years post-fire, but then cooled by 0.15 °C/yr in the subsequent eight years, while temperatures at the control site remained relatively stable. Permafrost cores collected from ice-wedge troughs (n = 41) and polygon centers (n = 8) revealed the presence of a thaw unconformity, that in most cases was overlain by a recovered permafrost layer that averaged 14.2 cm and 18.3 cm, respectively. Taken together, our observations highlight that the initial degradation of ice-rich permafrost following the Anaktuvuk River tundra fire has been followed by a period of thaw cessation, permafrost aggradation, and terrain stabilization.

Accurate Measurement of Temperatures in Industrial Grinding Operations with Steep Gradients.

Due to the continuously growing demands from high-added-value sectors such as aerospace, e-mobility or biomedical bound-abrasive technologies are the key to achieving extreme requirements. During grinding, energy is rapidly dissipated as heat, generating thermal fields on the ground part which are characterized by high temperatures and very steep gradients. The consequences on the ground part are broadly known as grinding burn. Therefore, the measurement of workpiece temperature during grinding has become a critical issue. Many techniques have been used for temperature measurement in grinding, amongst which, the so-called grindable thermocouples exhibit great potential and have been successfully used in creep-feed grinding operations, in which table speed is low, and therefore, temperature gradients are not very steep. However, in conventional grinding operations with faster table speeds, as most industrial operations are, the delay in the response of the thermocouple results in large errors in the maximum measured value. In this paper, the need for accurate calibration of the response of grindable thermocouples is studied as a prior step for signal integration to correct thermal inertia. The results show that, if the raw signal is directly used from the thermocouples, the deviation in the maximum temperature with respect to the theoretical model is over 200 K. After integration using the calibration constants obtained for the ground junction, the error can be reduced to 93 K even for feed speeds as high as 40 m/min and below 20 K for lower feed speeds. The main conclusion is that, following the proposed procedure, maximum grinding temperatures can be effectively measured using grindable thermocouples even at high values of table speed.

Mapping Permafrost Variability and Degradation Using Seismic Surface Waves, Electrical Resistivity, and Temperature Sensing: A Case Study in Arctic Alaska

AbstractSubsurface processes significantly influence surface dynamics in permafrost regions, necessitating utilizing diverse geophysical methods to reliably constrain permafrost characteristics. This research uses multiple geophysical techniques to explore the spatial variability of permafrost in undisturbed tundra and its degradation in disturbed tundra in Utqiaġvik, Alaska. Here, we integrate multiple quantitative techniques, including multichannel analysis of surface waves (MASW), electrical resistivity tomography (ERT), and ground temperature sensing, to study heterogeneity in permafrost’s geophysical characteristics. MASW results reveal active layer shear wave velocities (Vs) between 240 and 370 m/s, and permafrost Vs between 450 and 1,700 m/s, typically showing a low‐high‐low velocity pattern. Additionally, we find an inverse relationship between in situ Vs and ground temperature measurements. The Vs profiles along with electrical resistivity profiles reveal cryostructures such as cryopeg and ice‐rich zones in the permafrost layer. The integrated results of MASW and ERT provide valuable information for characterizing permafrost heterogeneity and cryostructure. Corroboration of these geophysical observations with permafrost core samples’ stratigraphies and salinity measurements further validates these findings. This combination of geophysical and temperature sensing methods along with permafrost core sampling confirms a robust approach for assessing permafrost’s spatial variability in coastal environments. Our results also indicate that civil infrastructure systems such as gravel roads and pile foundations affect permafrost by thickening the active layer, lowering the Vs, and reducing heterogeneity. We show how the resulting Vs profiles can be used to estimate key parameters for designing buildings in permafrost regions and maintaining existing infrastructure in polar regions.

Multisite evaluation of physics-informed deep learning for permafrost prediction in the Qinghai-Tibet Plateau

Prediction of the permafrost ground temperature is challenging due to its complex nonlinear process. Coupling physical models and machine learning has shown great potential in big data analysis, but its performance in permafrost prediction is still unclear. In this study, we proposed a physics-informed deep learning framework (i.e., PI-LSTM) to predict permafrost ground temperature profiles. The framework combines physical information with a long short-term memory (LSTM) network by two-stage training (pretraining and fine-tuning). The output of a Geophysical Institute Permafrost Laboratory 2 (GIPL2) model was used to pretrain the LSTM model. Borehole ground temperature measurements were used to fine-tune the pretrained LSTM model. Validation at multiple sites in various situations in the Qinghai-Tibet Plateau (QTP) shows that the accuracy and efficiency of the PI-LSTM model are dramatically higher than those of the original LSTM or GIPL2 model. Depending on the fine-tuning data sampling frequencies, the performance of the PI-LSTM model improved by an average of 27% (6–56%) and 69% (64–71%) compared to the LSTM and GIPL2 models, respectively. Even when only one year of observations was used to fine-tune the model, the RMSE of the simulated near-surface ground temperature profiles in the next decade did not substantially decline. The incorporation of physical information also contributes to the simulation efficiency. The PI-LSTM model converges faster than the LSTM model, and the training epochs are reduced by 70% (67–73%) during the fine-tuning step. This study demonstrates that integrating physical information into deep learning is promising for improving permafrost predictions.

Design and Experiments of a Naturally-Ventilated Radiation Shield for Ground Temperature Measurement

Temperature sensors may produce a measurement error of up to 1 °C because of the influence of solar radiation. In order to obtain a relatively minimal temperature error, a new temperature observation system was proposed in this paper for measuring surface air temperatures. Firstly, a radiation shield was designed with two aluminum plates, eight vents, and a multi-layer structure which is able to resist direct solar radiation, reflected radiation, and upwelling long-ware radiation, as well as ensuring the temperature sensor probe could work effectively. Then, the effect of different solar radiation intensities, wind speeds, scattered radiation intensities, long-wave radiation intensities, and underlying surface reflectivity levels on radiation error was calculated through a computational fluid dynamics (CFD) method. The mapping relationship was established between the various influencing factors and the solar radiation error. A back-propagation (BP) network algorithm was used to fit the discrete data obtained from the simulation to obtain the solar radiation error correction equation. Finally, the solar radiation error correction equation was verified. Outdoor experiments were conducted to confirm this system’s measurement accuracy. According to the experimental findings, the root-mean-square error was only 0.095 °C, which is a relatively high degree by which to reduce the temperature error. In addition, the average difference between the corrected value of the temperature observation system and the reference value was barely 0.084 °C.

Surface Energy Budget, Albedo, and Thermal Inertia at Jezero Crater, Mars, as Observed From the Mars 2020 MEDA Instrument

AbstractThe Mars Environmental Dynamics Analyzer (MEDA) on board Perseverance includes first‐of‐its‐kind sensors measuring the incident and reflected solar flux, the downwelling atmospheric IR flux, and the upwelling IR flux emitted by the surface. We use these measurements for the first 350 sols of the Mars 2020 mission (Ls ∼ 6°–174° in Martian Year 36) to determine the surface radiative budget on Mars and to calculate the broadband albedo (0.3–3 μm) as a function of the illumination and viewing geometry. Together with MEDA measurements of ground temperature, we calculate the thermal inertia for homogeneous terrains without the need for numerical thermal models. We found that (a) the observed downwelling atmospheric IR flux is significantly lower than the model predictions. This is likely caused by the strong diurnal variation in aerosol opacity measured by MEDA, which is not accounted for by numerical models. (b) The albedo presents a marked non‐Lambertian behavior, with lowest values near noon and highest values corresponding to low phase angles (i.e., Sun behind the observer). (c) Thermal inertia values ranged between 180 (sand dune) and 605 (bedrock‐dominated material) SI units. (d) Averages of albedo and thermal inertia (spatial resolution of ∼3–4 m2) along Perseverance's traverse are in very good agreement with collocated retrievals of thermal inertia from Thermal Emission Imaging System (spatial resolution of 100 m per pixel) and of bolometric albedo in the 0.25–2.9 μm range from (spatial resolution of ∼300 km2). The results presented here are important to validate model predictions and provide ground‐truth to orbital measurements.

Construction of emergency snow shelters using the results of air, snow and ground temperature measurements

This paper presents the use of ground, snow, and air temperature measurements for the construction of makeshift snow shelters. In Poland, in the coldest places (the Tatra Mountains, the Orava Basin) the temperature values at the contact of the ground surface with the snow cover usually oscillate in the range from 0°C to −3°C. Therefore, when constructing snow shelters, a snow insulation layer should not be left on the ground inside the shelter, which blocks the heating of the shelter interior by the heat accumulated in the ground A very big influence on the temperature inside snow shelters is the size of the entrance opening and the height of its location. The larger the opening and the higher it is located in relation to the ground, the lower the temperature values and the greater the vertical thermal gradient occur inside the shelter. The temperature in a properly constructed snow shelter is regulated by covering the entrance hole. The thickness of the walls, and especially the roof of the shelter, should not exceed 40 cm. Walls with a thickness of 30 cm provide sufficient thermal insulation.

Geology, Structure, Ground Temperature and Groundwater Level in Aquifer Taliks in the Shestakovka River Basin, Eastern Siberia

The objective of this study was to evaluate subaerial taliks’ geology, configuration, ground temperature and groundwater level in the continuous permafrost environment of Central Yakutia (Eastern Siberia). The study included geophysical surveys, borehole drilling and measurements of ground temperature and groundwater level variation in a talik aquifer in the Shestakovka research watershed. The talik occupies a gentle, sandy slope covered by a sparse pine forest. Its thickness varies from 3 to 17 m. The talik has several water-conducting branches along its slope. The seasonal thaw layer outside the talik and the talik itself form a single aquifer at the end of the summer. Water-saturated deposits in the talik have a temperature of about 0 °C throughout the year and do not freeze because of the constant filtration of water through the pores and convective heat transfer. Although the groundwater level is relatively close to the land surface, at a depth of just 1–3 m, it has very weak response to snowmelt and precipitation events. The maximum groundwater level occurs in February under cryogenic pressure due to deep seasonal ground freezing above the talik aquifer. Complicated relations between the landscape and the groundwater in the given geological conditions lead to the long-term existence of talik aquifers in the continuous permafrost environment.

Assessment of permafrost disturbances caused by two parallel buried warm-oil pipelines: A case study at a high-latitude wetland site in Northeast China

Multiple studies demonstrate that narrow-linear strong disturbances triggered by pipeline engineering activities have resulted in rapid permafrost degradation. However, the extent, duration, and severity of permafrost disturbances induced by two parallel buried warm-oil pipelines remain unclear. Here, we examine the thermal disturbances of the China-Russia crude oil pipelines (CRCOPs I and II) on the surrounding permafrost. Ground temperature measurements on and off the right-of-way of the CRCOPs and an electrical resistivity tomography survey were conducted at a selected high-latitude wetland site in northeastern China. The observations showed that warm oil flow in pipelines dissipated heat to the surrounding soil, resulting in the thawing of underlying permafrost accompanied by the formation and development of thaw bulbs around the pipes. Currently, the thaw bulb of CRCOP-I was about four times as large as that of CRCOP-II, mainly due to the longer 7-year working duration of CRCOP-I. To quantify the permafrost disturbances around the pipeline, a conductive heat transfer model was established. A numerical simulation of the soil thermal regime around the pipeline suggested the initial growth of the thaw bulb was quite fast but gradually slowed with time, of which the shape was modified to ellipse from a semicircle. The existence of CRCOP-II would accelerate the warming of permafrost on the CRCOP-I right-of-way due to the small separation distance between them. We expect that the thaw bulbs of the two pipelines will expand larger than previously estimated due to the adverse effects of pipeline settlement and surface water flow, sparking a wider permafrost disturbance.

Field measurement and numerical investigation of artificial ground freezing for the construction of a subway cross passage under groundwater flow

Artificial ground freezing is an environmentally friendly and reliable method to provide temporary ground improvement and groundwater isolation under adverse geological and hydrological conditions. Groundwater flow supplies a substantial source of heat which has an undesirable impact on the closure of frozen soil body. Furthermore, the phenomenon of frost heave and thaw settlement may threaten the surrounding structures. In terms of a ground freezing case in Beijing Metro Line 19, field measurement of ground temperature and deformation were conducted for the prediction of the formation of frozen curtain and the site stability. A hydro-thermal coupling model considering the effect of groundwater flow and phase transition was proposed to quantify the temperature distribution. The numerical model considers the soil particles, crystal ice and liquid water as separate phases, and thermal parameters as variable values related to temperature. Through two basic physical laws and corresponding governing equations, the model captures the relevant coupled relationship in heat and mass transfer. The proposed model is validated by means of the field measured data. Furthermore, the influence of groundwater velocities on the closure of frozen curtain was investigated. The results indicate groundwater flow has an adverse influence on the formation of freezing curtain, even leading to a failure to the closure. The thickness and temperature of frozen curtain with a groundwater velocity of 2 m/d can attain the design values after freezing for 50 days. Moreover, the ground and tunnel deformation in the process of freezing construction were well controlled.

Study on temperature of cylindrical wet grinding considering lubrication effect of grinding fluid

The improved cylindrical wet grinding temperature (ICWGT) model considering the lubrication effect of the grinding fluid is established and solved numerically. In doing so, the Newton–Raphson method is used to solve the hydrodynamic pressure of grinding fluid, and the fast Fourier transform (FFT) method is employed to accelerate the deformation calculation. Furthermore, the convective heat transfer coefficient (CHTC) is calculated based on the heat transfer theory, and the moving heat source method is adopted to obtain the grinding temperature. Meanwhile, the effectiveness of ICWGT is verified through the grinding temperature measurement experiment of alloy steel. Then, the cylindrical wet grinding temperature for alloy steel considering the lubrication effect of grinding fluid is studied and compared at varied grinding process parameter, and some rules are revealed.

Control of Short‐Stature Vegetation Type on Shallow Ground Temperatures in Permafrost Across the Eastern Canadian Arctic

AbstractThe Arctic has warmed three times the rate of the global average, resulting in extensive thaw of perennially frozen ground known as permafrost. While it is well understood that permafrost thaw will continue and likely accelerate, thaw rates are nonuniform due, in part, to the expansion of Arctic trees and tall shrubs that may increase ground temperatures. However, in permafrost regions with short‐stature vegetation (height &lt; 40 cm), our understanding of how ground temperature regimes vary by vegetation type is limited as these sites are generally found in remote high‐latitude regions that lack in situ ground temperature measurements. This study aims to overcome this limitation by leveraging in situ shallow ground temperatures, remote sensing observations, and topographic parameters across 22 sites with varying types of short‐stature vegetation on Baffin Island, Canada, a remote region underlain by rapidly warming continuous permafrost. Results suggest that the type of short‐stature vegetation does not necessarily correspond to a distinct shallow ground temperature regime. Instead, in permafrost regions with short‐stature vegetation, factors that control snow duration, such as microtopography, may have a larger effect on evolving ground temperature regimes and thus permafrost vulnerability. These findings suggest that anticipating permafrost thaw in regions of short‐stature vegetation may be more nuanced than previously suggested.

Sex and Body Colour Affect the Variation in Internal Body Temperature of Oedaleus decorus asiaticus in Natural Habitats in Inner Mongolia, China

Oedaleus decorus asiaticus is one of the most harmful locusts in agricultural and pastoral areas in China. Plagues of this grasshopper can aggravate grassland degradation and cause huge damage to the livestock industry. Fungal biopesticides are seen as a suitable means of controlling grasshoppers and locusts. However, the efficiency of fungal biopesticides is dependent on temperature. Currently, there is limited knowledge on the thermal biology of this grasshopper in natural habitats. In this study, ground temperature measurements were made in conjunction with measurements of internal body temperatures using thermocouples and hand-held thermometers. The grasshoppers were randomly caught during the daytime in 2017 and 2018 in eight different locations in Inner Mongolia Autonomous Region, China. Our results indicated that the average internal body temperature of nymphs as well as adults of O. d. asiaticusis was higher than the ground temperature and that it increases/decreases with increases/decreases in ground temperature, respectively, during the daytime. Moreover, the adult internal body temperature is significantly higher than that of the nymphs at different times of the day, specifically around 6:00, 10:00, 13:00, and 18:00. Female internal body temperatures were significantly higher than those of the males by an average of 0.90 °C. Additionally, the average internal body temperature of the brown morphs was higher than that of the green morphs by approximately 1.17 °C. These findings demonstrate that brown morph insects might be more tolerant of fungal biopesticides and hence the biopesticides may take longer to kill them. Hence, ecophysiological adaptations to climate change may affect how fungal biopesticides could be used in the future.

Experimental investigation into the potential of using a shallow ground-cooled condenser in Lebanon

The aim of this paper is to investigate the potential of using shallow geothermal energy in Lebanon for cooling a power cycle. The study includes ground temperature measurement, operating system management, and pressure drop assessment. Temperatures were monitored at six positions underground reaching to a depth of 2 m in Bekaa-Lebanon during the whole of 2020. The temperature sensors were placed at depths of 0.3, 0.6, 1, 1.3, 1.6, and 2 m underground. At 2 m depth, the ground temperature showed high stability with an annual temperature difference of 7 °C, while that of high and low ambient temperatures were 40 °C and 33 °C, respectively. Based on the comparison between ambient and ground temperatures, the ground cooling system can operate 207 days/year partially with full operations of 51 days. This shows that shallow geothermal energy has a great potential to activate a ground-based cooling system in this region. However, to avoid heat accumulation, use of another heat exchanger is recommended to support the ground cooling system. This heat exchanger can also provide coolth compensation when the power cycle is turned off. The pressure drop inside the heat exchangers was found to be highly significant, hence, it was essential to add an intermediate water loop between the power cycle and the ground loop.

Multi-Parameter Protocol for Geocryological Test Site: A Case Study Applied for the European North of Russia

An increase in air temperature leads to a significant transformation of the relief and landscapes of the Arctic. The rate of permafrost degradation, posing a profound change in the Arctic landscape, depends on air temperature, vegetation cover, type of soils, surface and ground waters. The existing international circumpolar programs dedicated to monitoring the temperature state of permafrost TSP (Thermal State Permafrost) and active layer thickness CALM (Circumpolar Active Layer Monitoring) are not sufficient for a comprehensive characterization of geocryological conditions. Yet, no standardized protocol exists for permafrost monitoring and related processes. Here, we propose a novel multi-parameter monitoring protocol and implement it for two sites in the European part of the Russian Arctic: the Yary site along the coast of the Baydaratskaya Bay in the Kara Sea (68.9° N) within the continuous permafrost area and the Hanovey site in the Komi Republic (67.3° N) within the discontinuous permafrost area. The protocol includes drilling boreholes, determining the composition and properties (vegetation cover and soils), snow cover measurement, geophysical imaging, active layer estimation and continuous ground temperature measurements. Ground temperature measured in 2014–2020 revealed that amplitudes of surface temperature fluctuations had no significant differences between the Yary and Hanovey sites, while that the mean annual temperatures between the areas had a considerable difference of greater than 3.0 °C. The period of the presence of the active layer changed with the year (e.g., ranging between 135 and 174 days in the Yary site), showing longer when the air temperatures in summer and the preceding winter were higher. Electrical resistivity tomography (ERT) allowed determining the permafrost distribution and active layer thicknesses. Thermometry results were consistent with our geophysical data. Analyzing the composition and properties of frozen soils helped better interpret the data of geophysical and temperature measurements. By integrating the study of the soil properties, ground temperatures, and ERT, our work allowed us to fully characterize these sites, suggesting that it helps better understand the thermal state at any other research sites in the European north of Russia. Our suggested monitoring protocol enables calibrating and verifying the numerical and analytical models of the heat transfer through the earth’s surface.

Study on heat transfer characteristics of the deep-buried ground heat exchanger under different multi-pipe layouts

The pipe group layout and buried pipe spacing in large-scale applications are of great significance for guiding the design of pipe group systems and improving the utilization potential of regional geothermal resources. This work takes a deep-buried coaxial double-pipe heating project at a depth of 2,539 m in Xi'an as an example. It establishes three-dimensional full-scale numerical models that couple the internal and external heat transfer with a multi-pipe system based on the measured ground temperature distribution, ground thermophysical parameters, and an in-situ experiment. The multi-pipe models are divided into two categories based on the pipe layout's minimum basic unit: the straight-line and the equilateral triangle models. Both model categories contain three independent deep-buried coaxial double-pipes, and each model involves four spacings of buried pipes (5 m, 10 m, 15 m, and 20 m). Based on the established models, the heat transfer characteristics of buried pipes under different pipe layouts and buried pipe spacing are studied, and the influences of ground thermal conductivity on the heat transfer in multiple pipes are discussed. Consequently, this study provides a scientific reference for the design of pipe groups for large-scale utilization of geothermal energy in medium-deep layers.

Thermal Forcing of the Nocturnal Near Surface Environment by Martian Water Ice Clouds

AbstractWe explore the potential role of clouds in moderating the nighttime temperature within Gale crater, as observed by the Rover Environmental Monitoring Station (REMS) instrument suite aboard the Curiosity rover. Just prior to aphelion, the decreasing trend in minimum daily temperature within Gale slows down. We investigate if this is due to increased formation of twilight and nighttime clouds, re‐radiating heat and reducing atmospheric and surface cooling. While diurnal analysis of REMS temperatures shows brief atmospheric warmings of 3–5 K post‐sunset during the occurrence of these clouds, an absence of similar warmings in the ground temperature measurements make it unlikely that clouds are the primary source. Seasonally, however, clouds that persist overnight could cause a warming of daily minimum surface temperatures in the Ls∼20°–50° season. This period can serve as a baseline and allow the potential effects of clouds to be more clearly discerned in the REMS temperature measurements. For this season, and in the peak of the aphelion cloud belt season, our modeled atmospheric energy budget shows a nocturnal decay signature of downward IR reflected and re‐emitted flux consistent with the presence and impact of clouds. The expected approximate exponential decay of this flux post‐sunset is damped more heavily in cloudier seasons than less cloudy or dusty seasons, suggesting formation and thickening of ice clouds as atmospheric nighttime temperatures cool.