Formation Mechanism of Snow and Rain Spatial Distributions in the Kanto Plain

  • Tomohiro ICHIZAWA, 2014: Formation Mechanism of Snow and Rain Spatial Distributions in the Kanto Plain .

Abstract

In previous studies, snow and rain distribution using spatially detailed observation data hasn’t been much investigated. This study uses above distribution and conducts example analysis of two cases with difference in snow and rain distribution in the Kanto plain. In order to investigate a formation mechanism of snow and rain spatial distribution in the Kanto plain, it also analyze with above two case studies and numerical simulation.

In the snowfall case on 14 January, 2013, a low pressure system rapidly developed with travelling along the southern coast of Honshu Island and brought heavy snowfall in the Kanto Plain. As a result of example analysis with detailed snow and rain distribution, rainfall was observed in the west and east part of the Kanto Plain, snowfall was in the central part, which corresponds with air temperature distribution from 0 to 2℃. Some air temperature drops were observed at a hundred and several tens of meter points. The reproductive experiment suggests that above rainfall in the west part of is caused by the westerly winds blowing down along the mountains in the west part of the Kanto Plain. The result of sensitivity experiments shows that cooling of snow melting has an impact on snowfall in the central part of the Kanto Plain. The temperature change with terrain altitude influences snowfall in the northwesterly part.

In the second case on 6 February, 2013, a low pressure system passed through the southern coast of the Kanto Plain, snowfall was observed in the northwesterly part of the Kanto Plain, rainfall was in the southeasterly part. Spatially detailed observation data of snow and rain indicates growth and decay of the phenomena, which corresponds with surface temperature chance. This feature was well reproduced by a numerical experiment. The result of sensitivity experiments shows that the temperature change with terrain altitude plays an important role in snowfall in the northwesterly part in the Kanto Plain, and evaporation cooling effect of rain and melting cooling effect of snow influenced before beginning of snowfall and rainfall on the ground.

Key words: snow and rain distribution, spatially detailed observation data, numerical experiment, evaporation cooling of rain drop, melting cooling of snow