Sensitivity of the Northern Hemisphere warming trend to snowpack variability

Abstract

Abstract A marked decrease in land surface snow cover within the Northern Hemisphere under global warming will warm the atmosphere near the land surface. However, minimal information exists regarding the contribution of snowpack variation to inter-annual surface air temperature variability. The current study investigates the effects caused by snow water equivalent (SWE) change on surface air temperature (SAT). To this end, a SWE pacemaker experiment of AMIP-type is undertaken for the period 1901-2010, during which the MIROC6 atmospheric general circulation model’s SWE is continuously nudged towards SWE derived from an LMIP-type experiment. Compared to a reference MIROC6 simulation without SWE nudging, the spatial correlation of 1980-2010 inter-annual SWE trends in our experiment with those in GlobSnow observation data increased by 0.31 over the Northern Hemisphere. Similarly, the linear correlation of inter-annual SAT with reanalysis data is greater by 0.04, 0.04, 0.08, and 0.07 for autumn, winter, spring, and summer over the region from the reference experiment, respectively. It is shown that due to this SWE nudging, modeled inter-annual SAT change in the Northern Hemisphere becomes more accurate. Through a surface energy budget analysis, changes in SAT are attributed to changes in surface albedo, soil evaporation, and soil temperature. Areas of greater contribution of SWE variability to SAT variability appear to shift from south to north areas as snow melts. These results highlight surface albedo, snow hydrological, and land heat storage effects through which the SWE inter-annual trend on the land surface significantly controls atmospheric air temperature variability near the land surface.