Snow/Ice and Cloud Responses to Future Climate Change around Hokkaido

Abstract

Wintertime climate around Hokkaido is highly sensitive to fluctuations in snow and sea-ice. We examined future climate change in heavy snowfall region around Hokkaido, using the Pseudo-Global-Warming method (PGW) by a regional climate model. The boundary conditions of the PGW run were obtained by adding the difference between the future (2090s) and past (1990s) climates simulated by coupled general circulation models, into the 6-hourly reanalysis and daily sea surface temperature data. The PGW experiments show that snow depth decreases significantly over mountainous areas. However, snow cover decreases mainly over plain areas, which accelerates surface warming due to the decreased snow albedo. Despite the snow reductions, precipitation increases over the mountainous areas because of enhanced water vapor content. However, precipitation decreases over the Japan Sea and neighboring the coastal areas, suggesting a weakening of the convergent cloud band which is formed by convergence between cold northwesterly from the Eurasian continent and anticyclonic circulation over the Okhotsk Sea. Our results indicate the contrasting cloud responses to future climate change over the Japan and Okhotsk Seas in terms of meso-scale climate system.