Permafrost, active layer and meteorological data (2010–2020) from a relict permafrost site at Mahan Mountain, Northeast of Qinghai-Tibet Plateau

Relict permafrost presents an ideal opportunity to understand the impacts of climatic warming on the ground thermal regime since it is characterized by mean annual ground temperature close to 0 °C and relatively thin permafrost. The long-term and continuous observations of permafrost thermal state and climate background are of great importance to reveal the links between the energy balance on hourly to annual timescales, to evaluate the variations of permafrost thermal state over multi-annual periods and to validate the remote sensing dataset. Until now there are few data available in relict permafrost regions although those data are important to understand the impacts of climate changes on permafrost especially in the boundary regions between permafrost and seasonally frozen ground regions. In this study, we present 11 years of meteorological and soil data in a relict permafrost site of the Mahan Mountain on the northeast of the Qinghai-Tibet Plateau. The meteorological data are comprised of air and ground surface temperature, relative humidity, wind speed and direction, shortwave and longwave downward and upward radiation, water vapor pressure, and precipitation on half-an-hour timescale. The active layer data include daily soil temperature and soil moisture at five different depths. The permafrost data consist of ground temperature at twenty different depths up to 28.4 m. The high-quality and long-term datasets are expected to serve as accurate forcing data in land surface models and evaluate remote-sensing products for a broader geoscientific community. The datasets are available from the National Tibetan Plateau/Third Pole Environment Data Center (https://doi.org/10.11888/Cryos.tpdc.271838, Wu and Xie, 2021).

Sea surface features and internal waves in the sea

On several oceanographic cruises conducted by Andhra University, an unusual sea-surface phenomenon was observed which consisted of long streaks of alternately smooth and rough water. On one occasion at the northern end of "Swatch of No Ground", temperature structure was measured at the same time as a passing of such series of wide sea surface streaks.

Utilization of Thermally Activated Building System with Horizontal Ground Heat Exchanger Considering the Weather Conditions

The thermally activated building system (TABS) can reduce the peak load by integrating with the ground heat exchangers. When integrated, the cost of groundwork and stability of the ground temperature would counteract because the weather conditions would influence the ground temperature in shallow depth. However, previous studies on TABS assumed constant ground temperatures such as average outdoor air temperature. In this study, ground temperatures in different depths are simulated for their detailed investigations, and simulated results of ground temperature were applied to building energy simulations for observing the load-handled ratio (LHR), representing the peak load reduction by TABS evaluated in various weather conditions. Simulation results of ground temperatures from 1 m to 39 m depths show that the temperature stabilized at 2 m to 11 m depths depending on the characteristics of the outdoor air temperature. LHR increased as the ground depth increased because the ground temperature at shallow depths increased during peak hours. Ground depths of 8 m were found ideal for maintaining consistent LHR for all weather conditions. Detailed observation of ground temperature and its effect on LHR in various weather conditions can help system engineers design and operate the TABS with the ground system.

Long-Term Variability in Ground Thermal State in Central Yakutia’s Tuymaada Valley

This paper presents the results of long-term temperature monitoring at the Yakutsk and Zeleny Lug stations, which are experimental sites, for the thermal state of valley permafrost landscapes under the conditions of modern climate warming. An analysis of the long-term data from meteorological stations in the region clearly showed one of the highest trends of increase in the mean annual air temperature in the north of Russia. Here, we established quantitative regularities in the long-term variability of the ground temperature at the bottom of the active layer and at zero amplitude. The dynamics of the ground temperature of the layer of zero amplitude during climate warming indicate the thermal stability of permafrost. The main regulating factor of the thermal state of grounds in permafrost landscapes is short-term fluctuations in the regime of snow accumulation. Active layer thickness is characterized by low interannual variability, weak climate warming responses, and insignificant trends. The results of studies of the thermal regime of soils can be extended to the same types of valley landscapes in the Lena River, and are a reliable basis for predicting heat transfer in natural and disturbed landscapes.

The influence of solar heating upon ground temperature

To predict the superficial ground temperature due to solar radiation as a function of the depth and rock physical properties, the Finite Volume Method was employed upon an energy conservation model. ANSYS Transient Thermal was selected to simulate a 3D geological volume, 1625 m wide, 2000 m long and with variable height as a function of topographical data. As a result, the variability of ground temperature during a 24h day was assessed. A set of climatological data was used to evaluate the ground temperature for the colder periods. The numerical results were compared against the Kusuda and Achenbach’s analytical solution to evaluate the possibility of extending the validity of a widely used method, from daily to intraday data.

Initialization of Thermal Models in Cold and Warm Permafrost

Equilibrium modelling, also known as spin-up, is a technique for initializing a stable thermal regime in ground temperature models for permafrost regions. The results act as a baseline for subsequent transient analyses of ground temperature response to climate change or infrastructure. In practice, spin-up procedures are often loosely described or neglected, and the criteria by which a stable thermal regime is evaluated are rarely defined or presented explicitly. In this paper, model results show that no single criterion based on thresholds of inter-cycle temperature change can be used to identify a stable thermal regime in all spin-up scenarios. Results from simulations using a wide range of initialization temperatures and conditions show the number of spin-up cycles can range between 10 to 10,000, and a spin-up criterion as fine as 0.00001 ^oC/cycle is required to achieve a stable thermal regime suitable for deeper warm permafrost models. The implications of selected threshold criteria are examined in follow-up transient analyses and show that warm permafrost models can be highly sensitive to initial temperature profiles based on the criterion utilized. The results alert scientists and engineers to the importance of initialization on site-specific and regional permafrost models for transient ground temperature analyses.