Soil thermal conductivity (lambda), which describes the ability of the soil to transfer heat, is critical to understand the thermal regime of ground surfaces. In this study, in situ measurements of lambda were conducted at two field sites in the permafrost region of the central Qinghai-Tibet Plateau (QTP) and the results were used to evaluate 11 schemes of lambda at depths of 10-50 cm during the freeze-thaw cycle period. Our analyses revealed that lambda had a remarkable seasonal variation, due to the significant effects of soil moisture content and ice-water phase changes as temperature changed during the freeze-thaw cycle period. Among the selected schemes, the Johansen scheme, its three derivatives (i.e., the He scheme, Yang scheme and Zhao scheme), and the Campbell scheme were significantly superior to others. Moreover, the Johansen scheme ranked among the top schemes for frozen soil, while the Campbell scheme gave the most accurate values for unfrozen soil. The effects of different estimation methods of quartz content (q), dry lambda and the Kersten number (K-e) on the predicted schemes results were also evaluated. The results showed that, the methods used for the estimation of q and K-e had the greatest influence on the calculation results for the permafrost region. Overall, this research provides insights for the development of a lambda scheme for the permafrost region of the central QTP.

The representation of snow is a crucial aspect of land-surface modelling, as it has a strong influence on energy and water balances. Snow schemes with multiple layers have been shown to better describe the snowpack evolution and bring improvements to soil freezing and some hydrological processes. In this paper, the wider hydrological impact of the multi-layer snow scheme, implemented in the ECLand model, was analyzed globally on hundreds of catchments. ERA5-forced reanalysis simulations of ECLand were coupled to CaMa-Flood, as the hydrodynamic model to produce river discharge. Different sensitivity experiments were conducted to evaluate the impact of the ECLand snow and soil freezing scheme changes on the terrestrial hydrological processes, with particular focus on permafrost. It was found that the default multi-layer snow scheme can generally improve the river discharge simulation, with the exception of permafrost catchments, where snowmelt-driven floods are largely underestimated, due to the lack of surface runoff. It was also found that appropriate changes in the snow vertical discretization, destructive metamorphism, snow-soil thermal conductivity and soil freeze temperature could lead to large river discharge improvements in permafrost by adjusting the evolution of soil temperature, infiltration and the partitioning between surface and subsurface runoff.

With increasing global warming, the skiing season is shortened to different degrees all over the world. As a crucial way to ensure the sustainable development of the ski industry, snow storage has been gradually studied and applied in Europe. Covering thermal insulation materials is a key engineering measure for the success of snow storage. This study used numerical methods rather than an experimental method to evaluate the thermal insulation performance of nine snow storage coverage schemes in Harbin, Beijing, and Altay, China. We investigated the thermal insulation performance of nine snow storage coverage schemes (three natural materials and six artificial ones) using a solar radiation method and an implicit finite difference method. Sensitivity analyses were conducted, and the cost performance of schemes 5-9 were analyzed. Based on the cost and thermal insulation performance, we used schemes 4 (geotextile, straw bale), 5 (geotextile, extruded polystyrene foam), and 7 (geotextile, polyurethane foam) to evaluate the snow storage effects in Harbin, Beijing, and Altay. Results showed that among schemes 1-9, scheme 7 has the best thermal insulation performance. If natural materials are used, then scheme 3 gives the best thermal insulation performance. Among schemes 5-9, scheme 5 is the most economical. The heat transfer in Beijing is higher than that in Harbin and Altay, while the latter two show similar heat transfers. The combination of meteorological conditions and coverage schemes influence the melting rate of snowpacks. The melting rate of snowpacks can be reduced with an optimized coverage scheme. The proposed methods can serve the selection of coverage schemes for snow storage.

Dynamical downscaling generally performs poorly on the Tibetan Plateau (TP), due to the region's complex topography and several aspects of model physics, especially convection and land surface processes. This study investigated the effects of the cumulus parameterization scheme (CPS) and land-surface hydrology scheme (LSHS) on TP climate simulation during the wet season using the RegCM4 regional climate model. To address these issues and seek an optimal simulation, we conducted four experiments at a 20 km resolution using various combinations of two CPSs (Grell and MIT-Emanuel), two LSHSs (the default TOPMODEL [TOP], and Variable Infiltration Capacity [VIC]). The simulations in terms of 2-m air temperature, precipitation (including large-scale precipitation [LSP] and convective precipitation [CP]), surface energy-water balance, as well as atmospheric moisture flux transport and vertical motion were compared with surface and satellite-based observations as well as the ERA5 reanalysis dataset for the period 2006-2016. The results revealed that the model using the Grell and TOP schemes better reproduced air temperature but with a warm bias, part of which could be significantly decreased by the MIT scheme. All schemes simulated a reasonable spatial distribution of precipitation, with the best performance in the experiment using the MIT and VIC schemes. Excessive precipitation was produced by the Grell scheme, mainly due to overestimated LSP, while the MIT scheme largely reduced the overestimation, and the simulated contribution of CP to total precipitation was in close agreement with the ERA5 data. The RegCM4 model satisfactorily captured diurnal cycles of precipitation amount and frequency, although there remained some differences in phase and magnitude, which were mainly caused by the CPSs. Relative to the Grell scheme, the MIT scheme yielded a weaker surface heating by reducing net radiation fluxes and the Bowen ratio. Consequently, anomalous moisture flux transport was substantially reduced over the southeastern TP, leading to a decrease in precipitation. The VIC scheme could also help decrease the wet bias by reducing surface heating. Further analysis indicated that the high CP in the MIT simulations could be attributed to destabilization in the low and mid-troposphere, while the VIC scheme tended to inhibit shallow convection, thereby decreasing CP. This study's results also suggest that CPS interacts with LSHS to affect the simulated climate over the TP.