Climatic Regions of India Part 2: Characteristics

Climatic Regions of India

Part 2

Trewartha’s Classification of Climatic Regions

• G.T. Trewartha modified the climatic classification of Koeppen in 1954 and divides the country into four major climatic regions which are further sub-divided into seven meso-climatic divisions.

They are:

Tropical Rainforest Climate (Am)

• This climate is characterized by high temperatures (above 18.2 °C) and heavy precipitation (above 200cms).
• The western coastal plain and Sahyadris and parts of Assam and Meghalaya comes under this climatic region.
• The characteristic vegetation of this region is primarily dense evergreen forests.

The Tropical Savannah Climate (Aw)

• The mean annual temperature in this climatic type remains around 27°C while the mean annual rainfall is less than 100 cm and has a marked dry season.
• This climate type includes the greater parts of the Peninsular India, excluding the coastal plains and the western slopes of the Western Ghats.

The Tropical Steppe Climate (BS)

• The mean annual temperature in this climatic zone is about 27°C and receives an annual rainfall of less than 75 cm.
• It covers the rain-shadow area of the Western Ghats including parts of Maharashtra, Telangana, Andhra Pradesh, Karnataka, and Tamil Nadu.

The Sub-tropical Steppe Climate (BSh)

• This is a semi-arid climate and streches over parts of Gujarat, eastern Rajasthan, Mahanadi, Andhra Pradesh, and southern Haryana.
• The mean annual temperature in this climate region is above 27°C, however, the mean monthly temperature of January remains only about 15°C and annual range of temperature is significantly high.
• The mean annual rainfall is low and varies between 60 – 75 cm.

The Tropical Arid Climate (BWh)

• This refers to the climate in the region west of the Aravallis, stretching over the Thar Desert.
• The mean maximum temperature during the months of May and June often goes above 48°C.
• The mean annual rainfall is less than 25 cm with the lowest rainfall in the country is recorded in this climate in the district of Ganganagar.
• Consequenty, the majority of natural vegetation in this region is in the form of thorny bushes.

The Humid Subtropical Climate (Caw)

• This climatic region covers the greater parts of the Great Plains of India, stretching from Punjab to Assam.
• The mean monthly temperature for the coldest month of January is less than 18°C, while the maximum temperature during the summer season may cross 45°C.
• The average annual rainfall decreases from east to west, from 250 cm in the east to only about 65 cm in the west.

Mountain Climate (H)

• This climatic region covers the hilly parts of the states of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Arunachal Pradesh, as well as the hilly parts of north-east India.
• In this climate, the average temperature for the summer season measures around 17°C, while the average January temperature is as low as 8°C.
• The average temperature of all the months is, however, closely influenced by the slope of the mountains as well as the topographical features.
• In general, the rainfall decreases from east to west with the Western Himalayas receiving some amount of rainfall from the western disturbances during the winter season.

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