Weather and Climate: Classification of Climate, the Thermal Zones, Climatic Types

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Classification of Climate

The varied effects of the major weather elements in different parts of the world and also the varied nature of the earth’s surface give every location a distinct climate. Hence, the number of different climates is large. In order to easily understand and comprehend this large variety, the climate of the world has been classified into a few major groups, each having certain common important characteristics.

Image of classification of climate

Image of Classification of Climate

Although several attempts have been made by scholars to classify the climate of the world for the proper understanding of major climate types no single classification is perfect, as climate stands for the generalized and composite weather conditions. However, the Greeks, made the first attempt to classify the world climates on the basis of the distribution of temperature and insolation. They divided the world into five latitudinal thermal zones. The boundaries of these zones are fixed on the basis of the angle at which the sun’s rays strike the earth. The following are the thermal zones of the earth:

The Thermal Zones

Torrid Zone: It is the largest of the thermal zones. It covers almost half the area of the earth’s surface. It is situated between the Tropic of Cancer (23½oN) and the Tropic of Capricorn (23½o South). The sun’s rays are almost vertical throughout the year in this zone. The mid-day sun is overhead at the equator on equinoxes, i.e., on 21st March and 23rd September. It is also overhead at Tropic of Cancer on 21st June and at Tropic of Capricorn on 22nd December. The duration of day and night is always equal i.e., 12 hours each on the equator and they increase to 13 hours and 27 minutes at tropics. The range of temperature is lowest at the equator and it increases towards the tropics.

Temperate Zone: The temperate zones are on either side of the Torrid Zone. The North Temperate Zone lies between Tropic of Cancer (23½oN) and Arctic Circle (66½oN) The South Temperate Zone lies between Tropic of Capricorn (23½°S) and Antarctic Circle (66½°S) The sun is never overhead in this zone in winter season, the nights are longer and days are shorter and vice versa in summer. The difference between the duration of the day and night increases towards the poles. The maximum duration of day in summer and that of night in winter in the polar circles is 24 hours. When it is summer in the northern hemisphere it is winter in the southern hemisphere and vice versa.

Frigid Zones: Like the temperate zone, Frigid Zone is also found in both the hemispheres. The North Frigid Zone lies between Arctic Circle (66½oN) and North Pole (90oN). The South Frigid Zone lies between Antarctic Circle (66½oS) and South Pole (90oS). During winter season, the sun does not rise above the horizon for almost six months. These are the coldest regions of the world. The surface remains permanently frozen under thick snow.

Climatic Types

The concept of thermal zone is theoretical and explains the distribution of solar energy over the earth’s surface. There are several other factors besides the angle of the sun’s rays which influence the climate of a place. Keeping in view other factors responsible for the distribution and combined influence of temperature and rainfall, modern scientists have arrived at several classifications of climate and its types. The most widely used system of climatic classification in its various modified forms is that of Wladimir Koeppen (1846-1940). It is based upon temperature, precipitation, and their seasonal characteristics. The relationship of climate with the vegetation is also included with it. According to this scheme, the world has been divided into five climatic groups and they are further sub-divided into 13 climatic types. They are as follows:

Climatic Groups
Climatic Groups

Climatic Groups

Climatic Types

(A) Tropical climates (hot all seasons)

Af (i) Tropical rain forest

Aw (ii) Savanna Climate

Am (iii) Monsoon Climate

(B) Dry climates

Bw (iv) Desert Climate

Bs (v) Steppe Climate

(C) Warm temperate rainy or Middle latitude rainy climates (mild winters)

Cs (vi) Mediterranean Climate

Cw (vii) China Type Climate

Cf (viii)West European Climate

(D) Humid Middle latitude climates (severe winters)

Dw (ix) Taiga Climate

Df (x) Cool East-coast Climate

(xi) The Continental Climate

(E) Polar climates

Et (xii) Tundra Climate

Ef (xiii) Ice-cap Climate

In brief, it can be said that

  • Weather is the atmospheric condition of a place for a short period of time with respect to one or more of its elements. It is not permanent. Season is the period of a year which is characterized by a particular set of weather condition. It is mainly caused by the inclination of the earth’s axis and revolution of the earth round the sun. Its cycle is repeated year after year. Climate is the average weather conditions of a large area for the past several years. It is more or less permanent. Climate of any place or region is affected by several factors, such as distance from the equator, ocean currents, direction of mountains. slope and aspect, soil and vegetation cover etc. Ancient Greeks divided the world into torrid, temperate, and frigid zones based upon the distribution of temperature. Torrid zone is the hottest. The frigid zone is the coldest and the temperature zone lies in between the two. It has a mild temperature. The length of the day varies from equator to poles. The days and the nights are almost equal on the equator. The length of the day increases in summer and decreases in winter as we move towards the poles.

  • Climate types are the outcome of the classification based upon regions of their formation. W. Koeppen classified the world into five climatic groups, namely (A) Tropical Climate, (B) Dry Climate, (C) Humid Mid-latitudes Climate (mild winters), (D) Humid Mid-Latitudes Climate (severe winters), and (E) Polar Climate. His classification is based on temperature, precipitation, and their seasonal variation. He further sub-divided the climatic groups into 13 climatic types.

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