Evaluation of air–soil temperature relationships simulated by land surface models during winter across the permafrost region

Abstract

Abstract. A realistic simulation of snow cover and its thermal properties are important for accurate modelling of permafrost. We analyse simulated relationships between air and near-surface (20 cm) soil temperatures in the Northern Hemisphere permafrost region during winter, with a particular focus on snow insulation effects in nine land surface models, and compare them with observations from 268 Russian stations. There are large cross-model differences in the simulated differences between near-surface soil and air temperatures (ΔT; 3 to 14 °C), in the sensitivity of soil-to-air temperature (0.13 to 0.96 °C °C−1), and in the relationship between ΔT and snow depth. The observed relationship between ΔT and snow depth can be used as a metric to evaluate the effects of each model's representation of snow insulation, hence guide improvements to the model's conceptual structure and process parameterisations. Models with better performance apply multilayer snow schemes and consider complex snow processes. Some models show poor performance in representing snow insulation due to underestimation of snow depth and/or overestimation of snow conductivity. Generally, models identified as most acceptable with respect to snow insulation simulate reasonable areas of near-surface permafrost (13.19 to 15.77 million km2). However, there is not a simple relationship between the sophistication of the snow insulation in the acceptable models and the simulated area of Northern Hemisphere near-surface permafrost, because several other factors, such as soil depth used in the models, the treatment of soil organic matter content, hydrology and vegetation cover, also affect the simulated permafrost distribution.

Effects of short-term variability of meteorological variables on soil temperature in permafrost regions

“…bryophytes and lichens), the soil organic layer, and their spatial extent and heights are of major importance (Yershov, 1998;Gouttevin et al, 2012;Jafarov and Schaefer, 2016;Wang et al, 2016). Snow generally insulates the soil from changing atmospheric temperature.…”

“…361-369) (Goodrich, 1982;Zhang, 2005;Jafarov and Schaefer, 2016;Wang et al, 2016), one would expect no to little additional effects of changing air temperature fluctuations on soil temperature, in particular on subsoil and permafrost temperature. However, air temperature variability will have an impact on snow height indirectly through snow density (Abels, 1892) and also directly when temperature periodically rises above the melting point.…”

Uncertainties in coupled regional Arctic climate simulations associated with the used land surface model

“…Furthermore, the snow properties (e.g., density and conductivity) are more realistically described in CLM4. The inspection of the temperature gradient across the air to soil surface (Figure ) shows that HIRHAM5‐CLM4 simulates a positive surface temperature offset (soil is warmer than air temperature) of up to +10 K indicating a realistic snow insulation [ Koven et al , ; Wang et al , ]. In contrast, HIRHAM5 shows a very poor performance in representing the surface temperature offset.…”

Effects of variability of meteorological measures on soil temperature in permafrost regions

“…Also, first modelling results confirm such simple response of increasing future soil temperature and active-layer thickness (Schaefer et al, 2011;Koven et al, 2011;Lawrence et al, 2012;Peng et al, 2016). As a result of increasing soil temperature and active-layer thickness, heterotrophic respiration is suggested to increase because of the temperature-25 response of biochemical functions (Arrhenius, 1889;van't Hoff, 1896;Lloyd and Taylor, 1994) and the additional availability of decomposable substrate (Koven et al, 2015) potentially leading to a positive climate-carbon cycle feedback (Zimov et al, 2006;Beer, 2008;Heimann and Reichstein, 2008).…”

“…1998; Gouttevin et al, 2012;Wang et al, 2016). Therefore, in this study we first analyze effects of climate variability on these soil insulating layers for a later explanation of the ultimate effects on soil temperature.…”