Geography-ncert-notes / Geography NCERT Notes / Climate and Climatic Regions

Climate and Climatic Regions

  • Climate of a country includes the study of temperature, rainfall, atmospheric pressure as well as the direction and velocity of winds over a arge period of time.

Introduction to Climate:

  • The term "climate" originates from the Greek word Klima, signifying inclination, slope, or latitude.
  • The climate is defined as the average meteorological conditions at a location over an extended period.
  • Factors influencing climate include:
    • Latitudinal and longitudinal extent
    • Sea level
    • Distance from continents and oceans
    • Prevalent wind types
    • Precipitation patterns
    • Oceanic waves and currents
    • Relief features
    • Soil type
    • Local geographic characteristics

Classification of Climate:

  • The Greeks pioneered climate classification based on temperature, distinguishing between warm temperate and cold zones. These zones gradually extend from the Equator to the poles.
  • The continent of Asia spans from the Equator to the North Pole, encompassing diverse climate zones.
  • Regions with consistent climates are termed climatic regions.
  • Key factors include latitude, altitude, proximity to the sea, temperature, vegetation types, and the impact of evaporation. Among these, latitude is the primary determinant of an area's climate.

Diagrammatic Representation of World Climate

Koeppen's Scheme of Classification of Climate

  • The most widely used classification of climate is the empirical climate classification scheme developed by V Koeppen.
  • Koeppen identified a close relationship between the distribution of vegetation and climate.
  • He used the values of temperature and precipitation and related them to the distribution of vegetation and used these values for classifying the climates.
  • It is an empirical classification based on mean annual and mean monthly temperature and precipitation data.
  • He used capital and small letters to designate climatic groups and types.
  • Koeppen recognised five major climatic groups, four of them are based on temperature and one on precipitation.
  • The capital letters A, C, D and E delineate humid climates and B dry climates.
  • The climatic groups are sub-divided into types, designated by small letters, based on seasonality of precipitation and temperature characteristics
  • The seasons of dryness are indicated by the small letters f, m, w and s. (f-no dry season), (m-monsoon climate), (w-winter dry season) and (s-summer dry season).

Climate Types According to Koeppen

Group

Climate Types According to Köppen

Type

Letter Code

Characteristics

A

Tropical Humid Climate

Tropical wet

Af

No dry season

A

Tropical Humid Climate

Tropical monsoon

Am

Monsoonal, short dry season

B

Dry Climate

Subtropical desert

BWh

Low-latitude arid or dry

B

Dry Climate

Subtropical steppe

BSh

Low-latitude semi-arid or dry

B

Dry Climate

Mid-latitude desert

BWk

Mid-latitude arid or dry

B

Dry Climate

Mid-latitude steppe

BSk

Mid-latitude semi-arid or dry

C

Temperature C-Warm (Mid-Latitude Climates)

Subtropical

Cfa

No dry season, warm summer

C

Temperature C-Warm (Mid-Latitude Climates)

Dry hot summer

Cs

Dry hot summer

C

Temperature C-Warm (Mid-Latitude Climates)

Marine West coast

Cfb

No dry season, warm and cool summer

D

Cold Snow Climates (Continental)

Subarctic

Df

No dry season, severe winter

D

Cold Snow Climates (Continental)

Winter dry

Dw

Winter dry and very severe winter

E

Cold Climates

Tundra

ET

Polar ice cap

E

Cold Climates

Perennial ice

EF

Highland with snow cover

H

Highland

Highland

H

Mediterranean

H

Highland

No true summer

H

No true summer

  • The lowercase letters a, b, c, and d denote the severity of temperature.
  • The B-Dry climates are further categorized using capital letters S for steppe or semi-arid and W for deserts.

Group A: Tropical Humid Climates:

  • Tropical humid climate spans between the Tropic of Cancer and Tropic of Capricorn, characterized by the Sun being overhead throughout the year and the presence of the Inter Tropical Convergence Zone (ITCZ), resulting in a hot and humid climate.
  • The annual temperature range is minimal, with high annual rainfall. The tropical group comprises three main types:

Tropical Wet Climate (Af):

  • Found near the Equator in areas such as the Amazon Basin in South America, Western equatorial Africa, and the islands of the East Indies.
  • Experiences significant rainfall every month, with thunder showers in the afternoon.
  • Uniformly high temperature with negligible annual temperature range, fostering tropical evergreen forests with dense canopy cover and large biodiversity.

Tropical Monsoon Climate (Am):

  • Present over the Indian subcontinent, Northern Australia, and the North-Eastern part of South America.
  • Heavy rainfall occurs mainly in summer, while winters are dry.

Tropical Wet and Dry Climate (Aw):

  • Found North and South of Af-type climate regions, bordering dry climate on the Western part and Cf or Cw on the Eastern part.
  • Savannas grow in tropical regions 8° to 20° from the Equator, characterized by warm to hot conditions in all seasons.
  • Mean annual precipitation ranges from 80 to 150 cm, with a dry season typically longer than the wet season. Savanna landscapes feature tall grass and short trees, known as bush-veld, providing a habitat for diverse animals.
  • Extensive Aw climate is found to the North and South of the Amazon forest in Brazil, adjoining parts of Bolivia and Paraguay in South America, Sudan, South and Central Africa.

Group B: Dry Climates:

  • Characterized by very low rainfall inadequate for plant growth, covering large latitudes from 15° to 60° North and South of the Equator.
  • Divided into Subtropical Steppe (BSh), Subtropical Desert (BWh), Mid-latitude Steppe (BSk), and Mid-latitude Desert (BWk).
  • Subtropical Steppe (BSh) and Subtropical Desert (BWh):  Located in the transition zone between humid and dry climates.
  •  Subtropical Steppe receives enough rainfall for sparse grassland growth, while variability in rainfall affects life more in the Steppe than in the desert, often causing famine.
  • Mid-latitud