4:00 PM - 4:15 PM
[MIS01-19] Evaluation of Global warming response of snowpacks over Mt. Iwaki in northern Japan by using a 2-km resolution non-hydrostatic climate model and a physical snowpack model
Keywords:Physical Snowpack Model, Mt. Iwaki, Non-hydrostatic Regional Climate Model, Climate Change
Rising temperatures due to climate change will change the duration and properties of snowpack. Change in the properties of snowpack from dry to wet may cause a change in the occurrence of wet-avalanches. Therefore, it is important to estimate changes in amount of snow and properties of snowpack in snow covered areas, particular on mountain slopes.
The purpose of this study is to quantitatively estimate the change in amount of snow and properties of snowpack of at difference altitudes in the present climate (1980-1999) and in the future climate (2076-2095), when the global mean temperature will rise by about 4 K (RCP8.5 scenario). The three study sites are at the base point (438 m), hillside point (1,238 m), and top point (1,625 m) of Mt. Iwaki in Aomori, Japan. Numerical calculations are performed by combining the outputs of a non-hydrostatic regional climate model (NHRCM developed by MRI/JMA) and the snowpack transformation model (SNOWPACK). This study focused on melt forms, which is an indicator of melting conditions and is related to wet avalanches, and hoar (faceted crystals and depth hoar), which is a weak snow layer after snow accumulation. After obtaining bias-corrected values from weather and snow measurements of NIED's SW-Net at the hillside and JMA's AMeDAS at the base, the present and future climates were compared.
Estimates of snow depth based on NHRCM decreased at all three sites in the future climate. The maximum snow depths are found in March for the present climate, but it appears in February for the future climate. They are about 290 cm at the hillside point and 320 cm at the top point in March for the present climate, while about 140 cm at the hillside point and 160 cm at the top point in February for the future climate, respectively. This indicates snow thawing will occur at least one month earlier in the future climate. Because the temperature at the top point is about 2.5K lower than that at the hillside point and the amount of melting is less, the maximum decrease in snow depth is larger at the hillside point than at the top point. Snowpack could be observed in April at the base point in the present climate, and in May at the hillside point and top point, but is almost completely obliterated in the future climate in the month.
The ratio of melt forms to snow depth decreased in some months at the base point in the present climate, but continued to increase consistently in the future climate. At the hillside point and top point, the percentage of melt forms decreased from November to December in the present climate, but increased in the future climate. This indicates that the temperature increase is also causing melting in December. In addition, the rapid increase in melt forms occurred in March to April in the present climate, but February to March in the future climate, indicating that the peak of melting occurs about one month earlier. The peak of wet snow avalanches is estimated to be earlier because wet snow avalanches likely to occur when rapid increase in melt forms is observed.
The ratio of hoar to snowpack decreased during the entire period because of the predominance of melt forms at the base point in the future climate. The percentage of hoar decreased during the months when the percentage of melt forms increased significantly at the hillside point and top point of the future climate as well.
The purpose of this study is to quantitatively estimate the change in amount of snow and properties of snowpack of at difference altitudes in the present climate (1980-1999) and in the future climate (2076-2095), when the global mean temperature will rise by about 4 K (RCP8.5 scenario). The three study sites are at the base point (438 m), hillside point (1,238 m), and top point (1,625 m) of Mt. Iwaki in Aomori, Japan. Numerical calculations are performed by combining the outputs of a non-hydrostatic regional climate model (NHRCM developed by MRI/JMA) and the snowpack transformation model (SNOWPACK). This study focused on melt forms, which is an indicator of melting conditions and is related to wet avalanches, and hoar (faceted crystals and depth hoar), which is a weak snow layer after snow accumulation. After obtaining bias-corrected values from weather and snow measurements of NIED's SW-Net at the hillside and JMA's AMeDAS at the base, the present and future climates were compared.
Estimates of snow depth based on NHRCM decreased at all three sites in the future climate. The maximum snow depths are found in March for the present climate, but it appears in February for the future climate. They are about 290 cm at the hillside point and 320 cm at the top point in March for the present climate, while about 140 cm at the hillside point and 160 cm at the top point in February for the future climate, respectively. This indicates snow thawing will occur at least one month earlier in the future climate. Because the temperature at the top point is about 2.5K lower than that at the hillside point and the amount of melting is less, the maximum decrease in snow depth is larger at the hillside point than at the top point. Snowpack could be observed in April at the base point in the present climate, and in May at the hillside point and top point, but is almost completely obliterated in the future climate in the month.
The ratio of melt forms to snow depth decreased in some months at the base point in the present climate, but continued to increase consistently in the future climate. At the hillside point and top point, the percentage of melt forms decreased from November to December in the present climate, but increased in the future climate. This indicates that the temperature increase is also causing melting in December. In addition, the rapid increase in melt forms occurred in March to April in the present climate, but February to March in the future climate, indicating that the peak of melting occurs about one month earlier. The peak of wet snow avalanches is estimated to be earlier because wet snow avalanches likely to occur when rapid increase in melt forms is observed.
The ratio of hoar to snowpack decreased during the entire period because of the predominance of melt forms at the base point in the future climate. The percentage of hoar decreased during the months when the percentage of melt forms increased significantly at the hillside point and top point of the future climate as well.