Cold Snow Forest Climates (D)

Cold snow forest climates are the climates of the vast northern interiors of continents — places where winter is long, dark, and bitterly cold, and where the forest that grows is the boreal or taiga forest. These climates sit between roughly 40° and 70° north latitude, across the great landmasses of Europe, Asia, and North America. The key idea is that these are continental climates: far from the moderating influence of oceans, so the temperature swings between summer and winter are enormous.

The book divides this climate into two types, based on the moisture of the winter season. The first is Df — cold climate with humid winter. The second is Dw — cold climate with dry winter. The severity of winter increases as you move poleward — the higher the latitude, the harsher the cold season becomes.

Cold Climate with Humid Winters (Df)

This climate is found poleward of two other climate types: the marine west coast climate and the mid-latitude steppe. In other words, as you move inland and northward from those milder regions, you eventually enter the Df zone.

The defining features are straightforward:

• Winters are cold and snowy.
• The frost-free season is short — the growing period for plants is brief.
• The annual range of temperature is large, meaning summers are warm but winters are very cold.
• Weather changes are abrupt and short-lived — conditions can shift quickly rather than gradually.
• Moving poleward, the winters become even more severe.

So the picture is of a climate with a short, mildish summer and a long, harsh, snowy winter, where day-to-day weather is changeable.

Cold Climate with Dry Winters (Dw)

This type is much more restricted in extent, occurring mainly over northeastern Asia. The reason for its dryness lies in the behaviour of the atmosphere over this region.

In winter, a pronounced anticyclone (a high-pressure system) develops over the land. This high pressure suppresses precipitation and brings clear, intensely cold, dry conditions. In summer, this anticyclone weakens, and the change in pressure sets up a monsoon-like reversal of wind direction over the region.

The consequences are striking:

• Poleward, summer temperatures are lower. …