Maximum Ground Temperature Research Articles

Spatiotemporal characteristics and variability in the thermal state of permafrost on the Qinghai–Tibet Plateau

AbstractPermafrost degradation on the Qinghai–Tibet Plateau (QTP) has significant impacts on climate, hydrology, and engineering and environmental systems. To understand the temporal and spatial characteristics of permafrost on the QTP, we quantified the variation in active layer thickness (ALT), permafrost thermal state, and future permafrost change under different scenarios using observational data, reanalysis data, and the numerical permafrost model. Generally, ALT ranged from 0.5 to 6.0 m with an average of 2.39 m, and mean annual ground temperature (at a depth of zero annual amplitude for ground temperature) mainly ranged between 0 and −3°C with an average of −0.85°C. The soil temperatures in different layers based on the ERA5‐Land data revealed even stronger increasing trends, for example, 0.245, 0.245, 0.244, and 0.238°C/decade at depths of 0–7, 7–28, 28–100, and 100–289 cm from 1980 to 2021, compared to those during the period from 1960 to 2021, which were 0.153, 0.156, 0.155, and 0.149°C/decade, respectively. The average warming trends in annual mean soil temperature were 0.153 and 0.243°C/decade from 1960 to 2021 and 1980 to 2021, respectively. The average rate of thickening of the ALT among the 10 active layer observation sites was 2.84 cm/year. There was a significant warming trend in ground temperature above ~15 m with warming of 0.063 to 0.120, 0.026 to 0.182, 0.101 to 0.314, and 0.189 to 0.303°C/decade at the QTB01, QTB06, QTB08, and XDTGT sites, respectively, and yearly minimum ground temperatures exhibited stronger warming trends than maximum ground temperatures. In addition, the simulation revealed significant increases in ground temperature at the Xidatan (XDT) and Tanggula (TGL) sites under both historical and future Representative Concentration Pathway (RCP) scenarios, but the increases in ground temperature were significantly greater at TGL than XDT. These findings provide important information for understanding the variability in permafrost degradation processes and improving simulations of permafrost change under climate change on the QTP.

Assessing the Impact of a Shallow Geothermal System Operation through Multi-Layer Temperature Monitoring in a Mediterranean Climate

Shallow Geothermal Energy (SGE) exchanges heat with the ground. In continuous, long-term operation, the initial temperature field can be disturbed, and subsurface thermal changes can be developed. In this paper, the thermal impact of a SGE system under a Mediterranean climate is handled. Temperature monitoring was conducted on 15 investigation boreholes equipped with a total of 92 thermal sensors placed at specific depths. Investigation boreholes were drilled 1–2 m from SGE system borehole heat exchangers installed in a university building. The analysis handles a one-year monitoring period of SGE system operation. Temperature depth profiles, reaching up to 140 m depth, were registered with a 10 min time step, resulting in a large amount of data. Ground thermal conductivity was estimated experimentally and semi-empirically, allowing us to obtain, using a numerical model, the initial undisturbed ground temperature profiles and compare them with the monitored values. Climate data were recorded by the university meteorological station. Globally, the measured and computed data were coherent, and a non-negligible impact of the SGE system operation in the first year was observed. The building orientation as well as the nearby departments had significant impacts on the shallow ground temperature. Maximum ground temperature changes observed at depths higher than 10–20 m, ranging from 2 to 3 °C as observed in different boreholes, indicate that the system is operating efficiently.

Структура и изменение термальных полей южной группы Камбального вулканического хребта (Камчатка) по температурным съемкам грунтов

Ground temperature survey at three thermal fields of the southern group of the Kambalny volcanic ridge (South Kambalny Near, Central and Far thermal fields) was carried out. Their current state is characterized. The formation of temperature anomalies is determined by the peculiarities of the geological structure of each thermal field.The maps of temperature surveys obtained in 2021 and 1965 are compared. Changes in the conditions of convective heat flow unloading in the geologic structure of thermal fields are shown. The size of temperature fields on all geologic structures of the southern group of the Kambalny volcanic ridge have significantly increased over time. The area of the most warmed areas of thermoanomalies has increased. The maximum ground temperatures increased by 10 °С on average. Some thermoanomalies (boiling and pulsating water boilers and vapor-gas jets) increased their flow rates and (or) temperature. New warmed areas within the thermal anomalies were discovered.

Distribution Law of the Initial Temperature Field in a Railway Tunnel with High Rock Temperature: A Model Test and Numerical Analysis

The distribution of the initial temperature field of a high-rock-temperature tunnel is critical for determining the tunnel line and the construction scheme. This study used model testing, numerical analysis, and field measurement to investigate the initial temperature field distribution of a tunnel with high rock temperatures. A model test system was developed, and the experimental results show that the boundary conditions set by the model are reasonable. The results show that the temperature along the tunnel line is high in the middle and low at both ends. Obviously, the periodic boundary conditions have a significant influence on the temperature field distribution. Then, the corresponding two-dimensional unsteady numerical model is established, and the numerical model is verified by the model test. Next, the numerical model is applied to the actual Jiwoxiga tunnel, which is a high-rock-temperature tunnel. The results show that the maximum ground temperature in the direction of the Jiwoxiga tunnel line is 52.5 °C, the tunnel lengths with ground temperatures above 28 °C account for 96.25% of the total tunnel length, and the tunnel length with a ground temperature above 45 °C comes to nearly 1200 m. In addition, this result is also verified by the field drilling data and field-measured data after excavation. The effectiveness and accuracy of the numerical model are fully demonstrated. This study provides theoretical support for the design and construction of high rock temperature tunnels.

Spatial-temporal distribution of biogas production from agricultural waste per capita in rural China and its correlation with ground temperature

Biogas production from agricultural waste has played a key role in recent years in reducing the environmental pollution risk of agricultural waste and alleviating energy shortage in rural China. However, few studies have focused on the effect of ground temperature on biogas production from agricultural waste from a quantitative point of view and the solution to increasing the temperature of biogas digesters in the cold season to improve biogas production from agricultural waste in rural areas at a provincial scale. Here, we calculated the spatial-temporal distribution of biogas production from agricultural waste per capita in rural China from 2001 to 2016 and agricultural waste per capita in rural China in 2016. Furthermore, we analyzed the correlation between biogas production from agricultural waste per capita in rural China and ground temperature. Finally, we proposed a solution to increase the temperature of biogas digesters in rural China in the cold season after analyzing its energy utilization. Results showed that the biogas production from agricultural waste per capita in rural China was correlated with the average and maximum ground temperature in January, February, March, November, and December from 2001 to 2016. The results also indicated that the suggested heating mode of biogas production from agricultural waste in rural China differed greatly among provinces. The provinces with high agricultural waste per capita in rural areas and low averaged biogas production from agricultural waste per capita are Inner Mongolia, Heilongjiang, and Xinjiang, which needed the suggested heating mode of biogas production from agricultural waste for increasing the temperature of biogas digesters in rural China in the cold season. Our findings provide a reference for biogas production from agricultural waste, greenhouse gas emission reduction, and the spatial layout of energy utilization in rural China.

Decreased temperature variance associated with biotic composition enhances coastal shrub encroachment

Regime shift from grasslands to shrub-dominated landscapes occur worldwide driven by altered land-use and climate change, affecting landscape function, biodiversity, and productivity. Warming winter temperatures are a main driver of expansion of the native, evergreen shrub, Morella cerifera, in coastal landscapes. Shrub establishment in these habitats alters microclimate, but little is known about seasonal differences and microclimate variance. We assessed influence of shrubs on microclimate variance, community composition, and community physiological functioning across three vegetation zones: grass, transitional, and shrub in a coastal grassland. Using a novel application of a time-series analysis, we interpret microclimatic variance modification and elucidate mechanisms of shrub encroachment at the Virginia Coast Reserve, Long-Term Ecological Research site. As shrub thickets form, diversity is reduced with little grass/forb cover, while transpiration and annual productivity increase. Shrub thickets significantly reduced temperature variance with a positive influence of one day on the next in maximum air, minimum air, and maximum ground temperature. We also show that microclimatic temperature moderation reduces summer extreme temperatures in transition areas, even before coalescence into full thickets. Encroachment of Morella cerifera on the Virginia barrier islands is driven by reduced local exposure to cold temperatures and enhanced by abiotic microclimatic modification and biotic physiological functioning. This shift in plant community composition from grassland to shrub thicket alters the role of barrier islands in productivity and can have impacts on the natural resilience of the islands.

The impact of multiple climatic and geographic factors on the chemical defences of Asian toads (Bufo gargarizans Cantor)

Chemical defences are widespread in nature, yet we know little about whether and how climatic and geographic factors affect their evolution. In this study, we investigated the natural variation in the concentration and composition of the main bufogenin toxin in adult Asian toads (Bufo gargarizans Cantor) captured in twenty-two regions. Moreover, we explored the relative importance of eight climatic factors (average temperature, maximum temperature, minimum temperature, average relative humidity, 20–20 time precipitation, maximum continuous precipitation, maximum ground temperature, and minimum ground temperature) in regulating toxin production. We found that compared to toads captured from central and southwestern China, toads from eastern China secreted higher concentrations of cinobufagin (CBG) and resibufogenin (RBG) but lower concentrations of telocinobufagin (TBG) and cinobufotalin (CFL). All 8 climatic variables had significant effects on bufogenin production (ri>0.5), while the plastic response of bufogenin toxin to various climate factors was highly variable. The most important climatic driver of total bufogenin production was precipitation: the bufogenin concentration increased with increasing precipitation. This study indicated that the evolution of phenotypic plasticity in chemical defences may depend at least partly on the geographic variation of defensive toxins and their climatic context.

Quantifying Impacts of Mean Annual Lake Bottom Temperature on Talik Development and Permafrost Degradation below Expanding Thermokarst Lakes on the Qinghai–Tibet Plateau

Variations in thermokarst lake area, lake water depth, lake age, air temperature, permafrost condition, and other environmental variables could have important influences on the mean annual lake bottom temperature (MALBT) and thus affect the ground thermal regime and talik development beneath the lakes through their direct impacts on the MALBT. A lake expanding model was employed for examining the impacts of variations in the MALBT on talik development and permafrost degradation beneath expanding thermokarst lakes in the Beiluhe Basin on the Qinghai–Tibetan Plateau (QTP). All required boundary and initial conditions and model parameters were determined based on field measurements. Four simulation cases were conducted with different respective fitting sinusoidal functions of the MALBTs at 3.75 °C, 4.5 °C, 5.25 °C, and 6.0 °C. The simulated results show that for lakes with MALBTs of 3.75 °C, 4.5 °C, 5.25 °C, and 6.0 °C, the maximum thicknesses of bowl-shaped talik below the lakes at year 300 were 27.2 m, 29.6 m, 32.0 m, and 34.4 m; funnel-shaped open taliks formed beneath the lakes at years 451, 411, 382, and 356 after the formation of thermokarst lakes, with mean downward thaw rates of 9.1 m/year, 10.2 m/year, 11.2 m/year, and 12.0 m/year, respectively. Increases in the MALBT from 3.75 °C to 4.52 °C, 4.25 °C to 5.25 °C, and 5.25 °C to 6.0 °C respectively resulted in the permafrost with a horizontal distance to lake centerline less than or equal to 45 m thawing completely 36 years, 32 years, and 24 years in advance, and the maximum ground temperature increases at a depth of 40 m below the lakes at year 600 ranged from 2.16 °C to 2.80 °C, 3.57 °C, and 4.09 °C, depending on the MALBT. The ground temperature increases of more than 0.5 °C at a depth of 40 m in year 600 occurred as far as 74.9 m, 87.2 m, 97.8 m, and 106.6 m from the lake centerlines. The simulation results also show that changes in the MALBT almost have no impact on the open talik lateral progress rate, although the minimum distances from the open talik profile to lake centerlines below the lakes with different MALBTs exhibited substantial differences.

The impact of climatic and non-climatic factors on land surface temperature in southwestern Romania

Land surface temperature is one of the most important parameters related to global warming. It depends mainly on soil type, discontinuous vegetation cover, or lack of precipitation. The main purpose of this paper is to investigate the relationship between high LST, synoptic conditions and air masses trajectories, vegetation cover, and soil type in one of the driest region in Romania. In order to calculate the land surface temperature and normalized difference vegetation index, five satellite images of LANDSAT missions 5 and 7, covering a period of 26 years (1986–2011), were selected, all of them collected in the month of June. The areas with low vegetation density were derived from normalized difference vegetation index, while soil types have been extracted from Corine Land Cover database. HYSPLIT application was employed to identify the air masses origin based on their backward trajectories for each of the five study cases. Pearson, logarithmic, and quadratic correlations were used to detect the relationships between land surface temperature and observed ground temperatures, as well as between land surface temperature and normalized difference vegetation index. The most important findings are: strong correlation between land surface temperature derived from satellite images and maximum ground temperature recorded in a weather station located in the area, as well as between areas with land surface temperature equal to or higher than 40.0 °C and those with lack of vegetation; the sandy soils are the most prone to high land surface temperature and lack of vegetation, followed by the chernozems and brown soils; extremely severe drought events may occur in the region.

Variations in the ground temperatures of permafrost in the two watersheds of the interior and eastern Qilian Mountains

The Qilian Mountains, which are composed of a series of approximately northwest–southeast-oriented mountains, are one of main alpine permafrost areas in the Qinghai–Tibet Plateau in northwestern China. From east to west, variations in permafrost environments are remarkable. The source areas of the Shule River (SASR) and the Datong River (SADR) are located in the interior and eastern part of the Qilian Mountains. In this study, variations in the ground temperatures of permafrost in the two watersheds represented the characteristics of interior and eastern permafrost environments in the Qilian Mountains. A total of 20 and 30 boreholes, along with ground temperatures measured at 10–15 m depths, were collected in the two areas. The maximum ground temperature in the SASR was 0.7 °C, and the minimum was −3.4 °C. The variations in the ground temperatures can be explained by elevation and local slope facing. The lapse rates of the ground temperatures with elevation were 5.9 °C/km for the south-facing slope, 8.0 °C/km for the gentle flat terrain and approximately 5.7 °C/km for the north-facing slope. It was estimated that the 0 °C ground temperature was located at approximately 3800 m in the flat terrains, at approximately 3880 m on the south-facing slope terrains, and at approximately 3710 m on the north-facing slope terrains. In the SADR, the maximum and minimum ground temperatures were 2.54 and −2.78 °C, respectively. The elevation, vegetation types and soil moisture content can explain most of the variations in the ground temperatures. The lower limits of the permafrost were 3620 m for the wet meadow and 3710 m for the moist meadow. The lapse rates of the ground temperatures with elevation were 3.4 °C/km for wet meadow and 3.0 °C/km for moist meadow. The differences in the ground temperatures of the two areas were primarily caused by regional climatic differences, particularly the varying precipitation and evaporation. However, more areas must be studied to elucidate the regional differentiation of permafrost distribution and the underlying reasons for this differentiation.

Seed germination of the invasive species Piper aduncum as influenced by high temperature and water stress

SummaryPiper aduncum is a common woody weed throughout the tropics and a successful invader in many areas. As this species most often dominates roadsides and forest margins, and these habitats frequently experience extreme changes in temperature and water availability, it is important to understand how the seeds adapt to these stresses. This study investigated the effect of high temperatures and water stress, continuous, periodic or transient, on P. aduncum seed germination before or after imbibition. It was found that P. aduncum seeds exhibited only intermediate tolerance and did not germinate at temperatures above 35°C or water potentials below −0.6 MPa. However, this species is well adapted to local conditions, with fruit ripening in the rainy season, seed desiccation tolerance to eRH 8%, rapid germination under wet conditions, higher temperature tolerance than the maximum ground temperature, germination of most seeds after 60 h continuous heat treatment or daily periodic heat treatments up to 5 h at 40°C and insensitivity to 12 h heat treatment at 40°C during the whole germination process. The intermediate tolerance to high temperature and water stress of P. aduncum, in combination with local environmental conditions in Xishuangbanna, makes P. aduncum an intermediate invader in this area.

Active layer characterization by instrumented dynamic cone penetrometer in Ny-Alesund, Svalbard

Global warming may induce an increase of active layer thickness in the Arctic region. The freezing and thawing of the active layer can damage infrastructures such as roads, railways, and embedded pipe lines in cold regions. A few methods, however, have been proposed to characterize the active layer. The objective of this study is to evaluate the characteristics of the active layer by laboratory and field tests, especially using the instrumented dynamic cone penetrometer (IDCP). Geographical and geological characteristics of Ny-Alesund, Svalbard are introduced, and the geotechnical properties, microstructure observations, and thermal properties of the Ny-Alesund soils are investigated. In addition, subsurface temperatures monitored for a year are discussed. The IDCP, which is able to measure the energies transferred into the rod head and the cone tip, is applied to the evaluation of the strength variation and the thickness of the active layer in Ny-Alesund. During dynamic penetration tests, the IDCP can produce profiles of the corrected cone tip resistance as well as the dynamic cone penetration index (DCPI). The results show that the active layer thickness estimated from the DCPI and corrected cone tip resistance profiles is approximately 1700mm. Furthermore, the bottom of the active layer significantly corresponds to that estimated by the maximum ground temperature profile with a soil thermal diffusivity of 5.5·10−7m2·s−1. This study represents the characteristics of Ny-Alesund soils investigated with a variety of laboratory tests, and suggests that the IDCP may be effectively used for active layer characterization.

An experiment to test key hypotheses of the drivers of reptile distribution in subalpine ski resorts

SummaryAlpine and subalpine ecosystems support many endemic species. These ecosystems are increasingly under threat from human‐induced disturbances such as habitat loss and fragmentation as a consequence of ski resort development and expansion. However, limited peer‐reviewed research has investigated the impacts of ski‐related disturbances on wildlife, particularly on reptiles.To address this knowledge gap, we conducted reptile surveys to determine the patterns of reptile distribution and abundance in Australian ski resorts. Then, using a factorial experimental design, we investigated 1) the influence of temperature and predation in driving observed distributions and 2) how a common ski resort management practice – mowing of modified ski slopes – affected thermal regimes and rates of predation of reptiles on ski runs.We found that the removal of vegetation structural complexity through mowing resulted in significantly higher rates of predation on plasticine models, as well as significantly altered thermal regimes.Crucially, mown ski runs had higher maximum ground temperatures that frequently exceeded the recorded critical maximum body temperatures of the target species of lizards. Thus, mowing has the potential to render these areas unsuitable for thermoregulatory purposes for a large proportion of the potential activity period of reptiles.Together, modifications of the thermal environment and elevated rates of predation appear to explain the avoidance of ski runs by reptiles. To facilitate the persistence of reptiles in disturbed subalpine environments, management plans must focus on implementing strategies that reduce the impact of human activities that alter temperature regimes and predation rates on lizards.Synthesis and Applications. We suggest that the retention of structural complexity on ski runs (e.g. through the cessation of mowing during peak reptile activity periods) and/or revegetation with native plant communities will concurrently provide refuge from predators and buffer against extreme temperatures, making ski runs more hospitable to reptiles. Based on our findings, we emphasize that effective management strategies targeting subalpine biodiversity conservation require an understanding of the drivers that determine species distributions in these landscapes.

Observation of Ground Temperature at Shallow Layer of Different Dune Types in the Tazhong Area

Land surface temperature affects the capability of long wave radiation,and it is an important parameter for studying climate change. The variation of air temperature and precipitation was often stressed in studying climate change in the Taklimakan Desert in the previous studies,but ground temperature in the desert was infrequently studied. In this paper,MicroLite 16K LITE5016 was used to examine the spatial distribution and temporal variation of ground temperature at shallow layer of different dune types in the Tazhong area located in the central Taklimakan Desert,where oceanic airstream is difficult to arrive. The Tazhong area is characterized by a typical continental climate with frequently and intensely wind-blown sand movement. The area of mobile dunes in Tazhong occupies more than 80% of the total area of the Taklimakan Desert. Temperature variation here is drastic,the maximum temperature is as high as 45.6 ℃,and the diurnal-nocturnal temperature difference is over 40 ℃. The annual sunshine duration in this area is 2 700 hours,accumulated temperature ≥0 ℃ is over 4 000 ℃,and the total solar radiation is 5 700-6 000 MJ/m2. Precipitation in this area is low,the annual precipitation is no more than 50 mm and only 4-5 mm in minimum,and it is extremely arid climate. The values of ground temperature at different depths (0 cm,10 cm and 20 cm) over a mobile dune and an artificially-fixed dune in the Tazhong area were measured during the period from August 3rd to 10th,2009. The results are as follows:(1) Daily range of ground surface temperature was high in summer both for mobile dune and artificially-fixed dune,it was decreased with the increase of depth,and it was the lowest at depth of 20 cm; furthermore,the maximum ground temperature occurred 2 hours later from noon,and the minimum one occurred at dawn; (2) The ground temperature of artificially-fixed dune was lower than that of mobile dune; (3) The difference between ground temperature and air temperature was the highest in summer; (4) Wind speed affected significantly the ground surface temperature regardless of mobile dune or artificially-fixed dune.

Modeled impacts of changes in tundra snow thickness on ground thermal regime and heat flow to the atmosphere in Northernmost Alaska

Seasonal snow covers the tundra surface for up to nine months of each year on the Alaskan North Slope. Variations in the snow thickness could strongly influence the thermal regime of the underlying soil and permafrost, and the surface energy balance. The impacts of increases and decreases in the tundra snow thickness on the thermal regime of snow surface, active layer, and permafrost, and on the conductive heat flow to the atmosphere were investigated numerically, by using an improved surface energy balance approach based one-dimensional heat transfer model. The baseline inputs for the numerical model are mean daily meteorological data and surface albedos collected at Barrow, Alaska from 1995 through 1999. Based on a study for the long-term mean daily maximum and minimum snow thickness distributions at Barrow in the snow season of 1948 through 1997, a snow thickness factor was defined and five simulation cases were run for the snow season of 1997–1998 by changing the snow thickness factor. The modeled results indicate that changes in snow thickness have significant impacts on ground thermal regimes and conductive heat flow to the atmosphere. Decreasing the snow thickness by 50% led to the maximum ground temperature decrease of 1.48 °C at 0.29 m depth, and 0.72 °C at 3.0 m depth; the magnitude of the mean conductive heat flow to the atmosphere for December increase of 4.3 Wm − 2 . Increasing the snow thickness by 50% resulted in the maximum ground temperature increase of 1.44 °C at 0.29 m depth, and 0.66 °C at 3.0 m depth; the magnitude of the mean conductive heat flow to the atmosphere for December decrease of 1.57 W m − 2 . On an annual basis, variation in the snow thickness by 50%, the ground temperature variations of more than 0.25 °C occurred as deep as 8.0 m below the ground surface. The modeled results also show that changes in snow thickness have a relatively small influence on the snow surface temperature.

A potential climatic index for total Saharan dust: the Sun insolation

It is shown that the daily course of the total amount of dust in the atmosphere, based on the TOMS aerosol index (AI), is highly correlated (0.98) with the integrated daily solar insolation over the Sahara region for spatially and temporally averaged data. Moreover, the annual maximum is even reached nearly at the same day, i.e., the 17th (18th) June for the surface (top of the atmosphere) solar insolation, as compared to 21st June for the date of maximum atmospheric dust loading. Other factors like cloudiness, rainfall soil moisture, and wind probably play a more dominant role in smaller areas. The fact that on a very large scale, like the whole of the Sahara, the solar insolation becomes the one single forcing directly correlated with the total amount of dust in the atmosphere is suggesting a simple climatic index for the total dust loading in the atmosphere. This index is shown for the Saharan region only, while more studies are needed for other regions. The 3–4 day time‐lag between the maximum insolation and the maximum dust loading in the atmosphere is compared to about a one‐month delay with the maximum ground or air temperatures and may serve as an estimate to the surface response to the major forcing of the Sun. The maximum ground temperature, delayed to the 17th July, can be explained by the delay in the lagged‐heating of the deeper soil layers. The 3–4 day delay only with the Sun insolation is probably linked to the period in which the dust is maintained in the atmosphere until it is deposited. One application to the present finding may be for climate models, since such a high correlation for spatially and temporarily averaged data may be used as an integrated index for the total amount of Saharan dust and for potentially validating the complex model parameterizations in climate models.

Impact of the timing and duration of seasonal snow cover on the active layer and permafrost in the Alaskan Arctic

AbstractVariations in the timing and duration of seasonal snow cover are critical to the ground thermal regime at high latitudes, due to changes in surface conditions and the associated ground surface energy balance. This study uses a one‐dimensional heat transfer model with phase change, combined with a surface energy balance equation to analyse the impact of changes in the timing and duration of seasonal snow cover on the thermal regime of the active layer and permafrost. Based on meteorological data collected at Barrow, Alaska, a series of simulation cases was conducted by varying the snowpack onset date in autumn and the disappearance date in spring during 1997–98. Results show that the ground thermal regime is sensitive to variations in the timing and duration of seasonal snow cover. Delaying the snow cover onset date by 10 days in autumn and the disappearance date by 10 days in spring results in a decrease in ground temperature. The maximum ground temperature decreases at depths of 0.0, 0.5, 1.0, and 2.0 m were 9.0, 2.9, 2.0, and 1.1°C, respectively, and the mean annual ground temperature decreases were 0.7, 0.5, 0.4, and 0.4°C. Advancing the snow cover disappearance date by 10 days in spring leads to an increase in ground temperature. The maximum ground temperature increases at depths of 0.0, 0.5, 1.0, and 2.0 m were 6.6, 2.2, 1.5, and 0.7°C, and the mean annual ground temperature increases were 0.2, 0.2, 0.1, and 0.1°C, respectively. Variations in the timing and duration of seasonal snow cover also have an influence on active layer thickness, but the effect is limited. Copyright © 2003 John Wiley & Sons, Ltd.

Some features of the topography of mean monthly 300-mb surface over India

The range of variation of the monthly mean height of 300.mb surface over India suggest old classification of the radiosonde stations in India, Little relation is seen between the highest mean maximum ground temperature and the highest mean height of 300.mb surface, This surface is practically level over whole of India from June to September and later during the year, slopes down from south to north, from 70°N 'wards, the slope increasing every month upto January and falling thereafter. Over South India there is very the annual variation.