Impact of Land-Use Change on Winter Precipitation in Hokkaido, Japan

Abstract

The effect of historical land-use change on winter precipitation in Hokkaido, Japan is evaluated by sensitivity experiments using a regional climate model and past and current land-use maps. The regional climate model successfully simulates winter precipitation characteristics, such as heavy precipitation in central mountain areas and around the Japan Sea coast, and a gradual decrease in precipitation from west to east. A comparison of model simulations using 1850 and 1985 land-use maps shows that precipitation has decreased approximately 1.7 mm mon^-1, especially over deforested areas. This decrease is mainly a result of reduced evapotranspiration (approximately 2.4 mm mon^-1) from lower net radiation associated with increased snow cover and higher surface albedo. Meanwhile, precipitation has increased in mountainous areas and on leeward slopes as a result of intensified upward air motion, which is attributed to a decrease in surface roughness caused by deforestation and the strengthening of horizontal wind speeds.