Impact of climate change on snow distribution in Japan estimated using data from the remote weather stations (AMeDAS) and Spot VGT

Change of the amount of snow by climate change is possibly remarkable in Japan, because air temperature is relatively high as snowy area in the world. And the change of the amount of snow cover highly depends on the supply form of precipitation (rain or snow) in winter corresponding to the change of the temperature in addition to the change of precipitation. And vegetation distribution of Japan is highly affected by snow conditions (snow duration and snow accumulation). To evaluate the change of snow condition in Japan climate change, daily change of SWE of 1km mesh was estimated using daily precipitation and air temperature of AMeDAS(Automated Meteorological Data Acquisition System) data. And using this model, changes of SWE and snow cover period were estimated in condition of global warming. Daily air temperature and precipitation on 1km mesh were estimated over all of Japan by interpolation of the AMeDAS data. AMeDAS is a system that observes the temperature and precipitation, etc. per hour automatically in about 1,300 places (about 17km spacing) in Japan. And daily change of SWE of each point was calculated using degree-day method and threshold temperature for the distinction between snow and rain using these data. We used precipitation and air temperature data of AMeDAS for 23 years from 1980 to 2002. Snow melt coefficient and elevation dependency of winter precipitation of each grid were optimized by snow duration estimated using satellite data (S3 index of Spot VGT) from 1990 to 2000 To estimate the change in the snow accumulation for the years from 2031 to 2051 and from 2081 to 2100, we used the climate change scenario of a high-resolution Regional Climate Model with a 20-km mesh size (RCM20) developed at the Meteorological Research Institute based on the Special Report for Emission Scenario (SRES)-A2. Estimated snow duration was evaluated in 10 points of mountainous snow measurement stations. Averaged error was about 4 days from 1980 to 1999. And estimated SWE was evaluated at 14 points in Niigata and Gunma prefecture from 2000 to 2001. Averaged error of SWE was about 32% in this period. Estimated change of SWE and snow cover period according to air temperature rise was remarkable at plain field along Sea of Japan in main land. Estimated decrease of snow cover period in this area was more than 80% in condition from 2 to 3 degrees air temperature rise for the years from 2031 to 2051.