Unit 18

HUMID MESOTHERMAL (C) CLIMATES

Unit Overview

This unit examines the C climates of the Köppen climate classification system. The main sections are:

  • The perpetually moist (Cf) climates
  • The dry-summer (Cs) climates
  • The dry-winter (Cw) climates

The C climates tend to be located at lower latitudes within the middle latitude zone. The major C climates are the Cf climates, which are located typically on middle latitude land masses either at lower latitudes (e.g., Charleston, South Carolina) on the eastern side or higher latitudes on the western side (e.g., Seattle, Washington). These climates do not have a pronounced dry season from a climate perspective, and they receive much precipitation from frontal lifting (e.g., mid-latitude cyclones).

Cs climates are equator-ward of the Cf climates on the western side of landmasses. These Mediterranean climates are impacted heavily in the summer season by the eastern edge of subtropical high-pressure cells, thus the summers are exceptionally dry. In the winter, the subtropical high weakens, allowing mid-latitude cyclones to affect the Cs climates.

The Cw climate is very similar to the Aw climate. Cw climates can exist not only in the middle latitudes but also in highland areas of the lower latitudes.

Unit Objectives

  • To expand our understanding of the various C climates
  • To interpret representative climographs depicting actual conditions in these climate areas
  • To highlight a major environmental-climatic problem of many C climate areas¿drought


Glossary of Key Terms

Drought The below-average availability of water in a given area over a period lasting several months.
Mesothermal climate The moderately heated climates that are found on the equatorward side of the middle latitudes, where they are generally aligned as interrupted east- west belts; transitional between the climates of the tropics and those of the upper midlatitudes where polar influences begin to produce harsh winters.


Unit Outline

  • The perpetually moist (Ct) climate
    • (Cra) humid subtropical climate created by warm, moist air traveling around the western margins of the subtropical highs
      • located in southeastern comers of 5 major continents
      • rainfall totals almost as high as tropical rainforests
    • The marine west coast (Cfb, Crc) climate
      • occurs on coasts affected by the westerlies year round
      • Cfb climate is warmer than Crc climate
  • The dry-summer (Cs) climates
    • Mediterranean climate, abundant sunshine and long, dry summers
    • Csa climate is warmer than Csb
  • The dry-winter (Cw) climates
    • Similar to the tropical savanna climate, but more rainfall and cooler mean temperatures
      • winter dry season, sometimes called the subtropical monsoon climate
      • Cwa associated with high elevations in tropical latitudes, Cwb is cooler


Review Questions

  1. Describe generally the global distribution of C climates.
  2. Compare and contrast the Cr, Cs, and Cw climates.
  3. What were the causes and effects of the Drought of 2001?