Decadal Changes In Soil And Atmosphere Temperature Differences Linked With Environment Shifts Over Northern Eurasia

The difference between soil and air temperatures (Delta T) in a specified time is dependent on meteorological conditions, properties of soil and land covers. Understanding Delta T is critical in assessing land-atmosphere thermal interactions in changing environment. However, systematic knowledge of interannual variations and responses of Delta T to the environmental changes (e.g., snow cover and soil moisture) at decadal scales remain limited. Here, variations of the mean annual air and soil temperatures, and Delta T were investigated at 217 sites in northern Eurasia during 1981-2015. It is found that changes in the mean annual air and soil temperatures were inconsistent as the average increase in soil temperature was generally less than that of air. The relationships between trends in soil and air temperatures were significant in the upper ground (0.2 and 0.8 m) over the seasonal frost region but insignificant in the permafrost regions and deeper ground. During the period, widespread changes in Delta T occurred and closely responded to the environmental changes, but the relationships varied with soil depth. Among the tested factors, trends in snow cover thickness dominantly control trends in Delta T, followed by trends in snow cover duration and solar radiation. Both linear and nonlinear analyses indicate enhanced relationships between trends in snow depth and Delta T as depth increases. This study provides the first view of decadal trends in Delta T and conjunctions with the environmental changes during 1981-2015 over northern Eurasia. The findings are relevant to quantify land-atmosphere thermal interactions given impacts of future environmental changes.