Climatic Regions of India
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.
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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