Climatic Regions of Snowy Winter and Frosty Winter in Japan

Abstract

Snow and frost are remarkable weather phenomena of winter. But it is general that these phenomena do not occur at the same time at the same place. Therefore, we can detect two climatic regions according to such chara-cteristics of winter, i. e. snowy regions and frosty regions. Such divisions are also significant to research from an environmental point of view on climates, because snow and frost have also important roles on our daily lifes and productive activities. Using the observed number of snowy days and frosty days, we researched dates of arrivals, retreats and durations of winter at various places and which is a predominant phenomenon among snow and host at each locality. 1) Frosty regions can be found at the Pacific Side of Japan and snowy regions are the Japan Sea Side. 2) An arrival of frost is about November and its retreat is April almost at every place in Japan. And generally speaking snow comes in December and ends at March. 3) Then at the Japan Sea Side, it is general that winter begins at December and ends at March both with snow. But at some places, it can be seen one or two months of frosty winter before and behind of these snowy months. (Cf. Tab.1) 4) Larger parts of Hokkaido are snowy. Frosty places can be found only at southeastern parts. In this region, frost and snow also begin to fall at October and end at April. Therefore, winter durations become t ro months longer than other regions. 5) At the Pacific Side, winter are comparatively longer than the Japan Sea Side. They continue from November to April. But at southern areas (Shikoku, Kyushu etc.), they are rather warmer and winter opens at December and closes at March. Especially at promontory of southern peninsulas, winter is very short. It is only one month. It begins at January and ends at that month. (3) Referring to the chi-square test, we considered that 3.8 days per month which have frost and snow respectively are significant as threshold values to recongnize an entrance or a retreat of winter. 4) Regional reprecentativenesses of snowy and frosty days as climatic elements are larger at the Japan Sea Side and smaller at the Pacific Side.