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Unit 19


Unit Overview

This unit examines the "cool" climates, which occur either in the upper-middle to higher latitudes, or at high-elevation locales, or both. The main sections are:

  • The major humid microthermal (D) climates
  • The polar (E) climates
  • High-altitude (H) climates

The D climates are located in the middle latitudes, predominantly in the interior portions of Northern Hemisphere continents. The E climates are located poleward of the D climates and receive little precipitation because of the lack of water vapour in the air. The H climates are located at high elevations, and as a result are relatively cold compared to surrounding climates. H climates can be considered anomalies when viewed from the regional perspective. Finally, owing to the location of pollutant-emitting facilities in the D climates and the prevalent westerly winds, acid precipitation is an important geographically displaced environmental problem in this zone.

Unit Objectives

  • To expand the discussion of typical D, E, and H climates and to interpret representative climographs for those zone
  • To highlight a major environmental-climatic problem of many climate regions: acid precipitation
  • To characterize the general influence of altitude on climatic conditions

Glossary of Key Terms

Acid precipitation Abnormally acidic rain, snow, or fog resulting from high levels of the oxides of sulfurs and nitrogen that exist as industrial pollutants in the air.
Highland climate Climate of high-elevation areas that exhibit characteristics of climates located poleward of those found at the base of those highlands; the higher one climbs, the colder the climate becomes - even in the low latitudes. Thus H climate areas are marked by the vertical zonation of climates.
Humid microthermal climate The weakly heated continental climates of the Northern Hemisphere's upper midlatitudes, where the seasonal rhythms swing from short, decidedly warm summers to long, often harsh winters; mostly confined to the vast interior expanses of North America and Eurasia poleward of 45 degrees N.
Permafrost The permanently frozen layer of subsoil that is characteristic of the colder portions of the D-climate zone as well as the entire E-climate zone; can exceed 300 m (1000 ft) in depth.
pH scale Used to measure acidity and alkalinity of substances on a scale ranging from 0 to 14, with 7 being neutral; below 7 increasing acidity is observed as 0 is approached, while above 7 increasing alkalinity is observed as 14 is approached.
Polar climate Climate in which the mean temperature of the warmest month is less than 10° C (50° F); the tundra (ET) subtype exhibits warmest-month temperatures between 0° C (32° F) and 10° C (50° F), while in the (coldest) icecap (EF) subtype the average temperature of the warmest month does not reach 0° C (32° F).
Vertical zonation Characteristic of H climates, the distinct arrangement of climate zones according to altitudinal position; the higher one climbs, the colder and harsher the climate becomes.

Unit Outline

  • The major humid microthermal (D) climates
    • Located poleward of meso thermal climates in Northern Hemisphere
    • Harsh winters and warm summers
    • Period longer than a month when temperature is below O°C (32°F)
    • Humid continental (Dfa/Dwa/,Dtb/Dwb) and taiga (Dfc/Dwc, Dfd, Dwd) climates
      • humid continental climates in upper-midlatitudes
      • taiga climate is subarctic
      • both humid continental and taiga are moist year round (Dt)
      • on interiors of large landmasses, dry-winter climates occur (Dw)
        • permafrost is a permanently frozen layer of topsoil
      • environmental problem of acid precipitation in D climate zones
  • The polar (E) climates
    • Located beyond the Arctic and Antarctic Circles (66 degrees N & S)
    • Six months of light in summer, six months of darkness in winter
      • extensive ice fields in winter months
    • Average temperature for warmest month is less than 10° C (50° F)
    • The tundra (ET) climate
      • warmest average monthly temperature between 0° C (32° F) and 10° C (50° F)
      • stunted trees, mosses, lichens
    • The ice cap (EF) climate
      • lowest annual temperatures on Earth
      • warmest monthly average temperatures are not above freezing
  • High-altitude (H) climates
    • Vertical zonation with altitude
      • climates become progressively colder with increasing altitude, mimic the pattern as climates progress from the equator to higher latitudes
      • tropical or desert climate, surface - 1200m [4,000 feet])
      • subtropical climate, 1200m [4,000 feet] - 2400m [8,000 feet]
      • mesothermal climate, 2400m [8,000feet] - 3600m [12,000 feet]
      • microthermal climate, 3600m [12,000feet] - 4800m [16,000 feet]
      • permanent ice and snow, above 4800m [16,000 feet]

Review Questions

  1. Compare and contrast the tundra (ET) and icecap (EF) climates.
  2. Describe the vertical zonation scheme of H climates.