Thornthwaite climate classification of India:
The following are the important points of Thornthwaite climatic classification:
- Thornthwaite presented climate classification in 1931, 1933, and 1948.
- In his 1933 presentation; gave the concept o precipitation effectiveness and temperature effectiveness.
- In his 1948 concept; gave the potential evapotranspiration concept
Evapotranspiration:
Combined, evaporation from the soil and transpiration from vegetation is called Evapotranspiration.
Precipitation effectiveness:
Plants' growth is not only dependent on precipitation but precipitation effectiveness.
Precipitation effectiveness P/E ratio=total monthly precipitation/ Evapotranspiration
P/E index= sum of 12-month P/E ratio.
Based on the P/E index, Thornthwaite classified five humidity regions:
- A ( P/E index>128)- Wet- Rainforest.
- B( P/E Index 64 to 127) - Humid- Forest
- C( P/E index 32 to 63)- Subhumid - Grassland.
- D(P/E index 16-32)- Semi Arid-Steppe
- E(P/E index less than 16)- Arid-Desert
Rainfall variation measures in the following alphabet:
r= rainfall all the year
s= rainfall deficient in summer
w= rainfall deficient in winter
d=rainfall deficient all over the year.
Temperature efficiency:
Temperature efficiency is calculated mean average temperature through the years.
Based on Temperature efficiency:
- A' tropical: T/E index more than 128.
- B' Subtropical: T/E index 64-127.
- C' Temperate: T/E index 32 - 63
- D' Taiga: T/E index 16-31
- E' Tundra: T/E index 1-15.
- F' Frost: T/E index 0.
Based on the above three-category variable:
- Precipitation effectiveness, rainfall variation, and temperature effectiveness, there are 32 main climatic regions and 120 subs climatic regions of the world.
- India has been divided into 12 climatic regions.
- A: Per humid
- B: Humid
- C1: Moist Sub Humid
- C2: Dry Sub Humid
- D: Semi-Arid
- E: Arid
- Western Ghats
- Most parts of the NorthEastern States
- Adjoining region of the Perhumid region
- Narrow belt Adjoining region of the humid region of Western Ghats.
- Eastern India comprises West Bengal and Orissa
- Northern Narrow belt of the Ganga basin.
- Part of Uttar Pradesh, Bihar, MP, Chhattisgarh, Jharkhand
- Western Maharastra and Southern Gujarat
- Part of Punjab and Haryana
- Eastern part of Rajasthan, Maharashtra, Karnataka, Lenangna
- Western Pat of Tamilnadu.
- Western Rajasthan
- Western Himalayan
- Rainshadow zone of western Ghats
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