Subarctic climate - akantaikikou

A cold climate unique to the subarctic zone. It is also called a cold or cool temperate climate. In the Köppen climate classification, it corresponds to climate D, where the average temperature of the coldest month is below -3°C and the average temperature of the warmest month is above 10°C. It is limited to the northern part of Eurasia and North America. In the Southern Hemisphere, there is almost no land at the corresponding latitude, so there is no subarctic climate as a living space. The winters are long and cold with snow. In summer, the daytime hours are long, so there is a lot of sunlight, and it becomes quite hot for a short period of time, and the annual temperature range is very large. It is the coldest region in the world except for Antarctica, and the freezing period of rivers, lakes, and harbors and the period of snowfall can last several months. In summer, low pressure areas develop and there is a lot of rain, making agriculture possible. The northern limit of agricultural activity is near the border between the number of months with an average monthly temperature of 10°C or higher for more than four months and the number of months with an average monthly temperature of 10°C or higher for less than three months. Based on the seasonal distribution of precipitation, the subarctic climate is divided into subarctic rainy climates with precipitation all year round (cold rainy climates, cold humid climates) and subarctic summer rainy climates with more precipitation in the summer (cold summer rainy climates, subarctic winter rainy climates). Based on vegetation, it can also be divided into coniferous forest climates (taiga climates) in the north and continental mixed forest climates in the south.

[Shuji Yamashita]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

亜寒帯に特有な寒冷な気候。冷帯気候または冷温帯気候ともいう。ケッペンの気候区分では、最寒月の平均気温零下3℃未満、最暖月の平均気温10℃以上のD気候に相当する。ユーラシア大陸と北アメリカ大陸の北部に限られる。南半球ではこれに対応する緯度にほとんど陸地はないので、居住空間としての亜寒帯気候は存在しない。積雪のある厳寒の冬は長い。夏は昼間時間が長いため日射量が多く、短期間ではあるがかなり高温になり、気温の年較差が非常に大きいのが特徴である。南極大陸を除くと世界中でもっとも寒冷な地域で、河湖や港湾の凍結期間や積雪期間は数か月にも達する。夏は低圧部が発達し、雨が多くなるので農耕が可能となる。農業活動の北限は、月平均気温10℃以上の月が4か月以上と3か月以下の境付近にある。亜寒帯気候は降水の季節配分から、年中降水のある亜寒帯多雨気候（冷帯多雨気候、冷帯湿潤気候）と降水が夏に多い亜寒帯夏雨気候（冷帯夏雨気候、亜寒帯冬季少雨気候）とに細分される。また植生に着目して、北部の針葉樹林気候（タイガ気候）と南部の大陸性混交林気候に二分することもある。

［山下脩二］

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