Climate Systems

 Subarctic Climate

Deep in the interior of high latitude continents lies the  subarctic climate. Like the humid continental climate, continentality plays a major role in determining the characteristics of the  subarctic climate.  Bitterly cold winters and mild summers result in the largest annual temperature range of any climate on Earth.

Figure 9.34 Snow covered coniferous forest, typical natural vegetation of the  subarctic climate. (Photo credit: T. Smylie, U. S. Fish and Wildlife Service.) Conical shape of coniferous trees helps capture insolation from low sun angles typical of the  subarctic.

Geographic Distribution

The subarctic climate is only found in the Northern Hemisphere because there is no large landmass at the same latitude in the Southern Hemisphere. Vast expanses of the  subarctic climate stretch across northern North America from Newfoundland to Alaska.  subarctic climate is found in northern Eurasia from Scandinavia through most of Siberia.

Controlling Factors

Located in a large continental landmass between 50^o to 70^o  latitude the  subarctic climate is removed from any moderating influence of an ocean. It therefore experiences a very large range in annual temperatures. During the summer it is dominated by the Westerlies and cyclonic activity, during the winter it is the Polar High and Easterlies. The  subarctic climate is noted for its long cold winters, no wonder given that it is found in the source region for continental polar air masses. Other air masses of significance are maritime polar and continental arctic.

Figure 9.35 Climograph for Yakutsk, Russia Latitude/Longitude = 62.1 N; 129.49 W Average Annual Temperature (C) = -10.08 Annual Temperature Range (C) = 63 Total Annual Precipitation (mm) =213 Summer Precipitation (mm) = 157 Winter Precipitation (mm) = 56

Distinguishing Characteristics

Temperature

The  subarctic climate has brief, cool summers and bitterly cold winters. The  subarctic experiences the lowest temperatures outside of Antarctica, and the largest annual temperature range of any climate. Though the summer is short, the day length is quite long with June days lasting  18.8 hrs at 60^oN. Daytime temperatures can rise above 25^o C (77^oF), while dropping to 10^o C (50^oF)during the evening. The freeze free period is of course short, being only three months long. However, a freeze can occur in any month.

Precipitation

Total annual precipitation in the  subarctic is fairly small, amounting to no more than 380 mm (15 in) to 500 mm (21 in) over the year. Most of the precipitation is cyclonic in origin and concentrated during the warmer months (except along coasts) where air masses are more humid. Notice that the summer precipitation at Yakutsk is three times that of winter. The extremely cold temperatures, coupled with the subsidence of the Polar High, are responsible for the meager precipitation that falls during the winter. 

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