RAS question
According to Koeppen's climate classification, the western desert region of Rajasthan falls under which climate type?
Correct answer: (B) BWhw — Hot desert (arid).
Under Koppen's climate classification, Rajasthan's western Thar Desert has the BWhw hot-desert, or arid, climate type.
Explanation
Under Koppen's scheme, Rajasthan's western Thar region is classified as BWhw, the hot-desert or arid climate type. It has scorching summers, dry winters, less than 25 cm of highly irregular rainfall, a large day-night temperature range, scarce water, and vegetation dominated by thorny shrubs and grasses. The Rajasthan Forest Department / Arid Forest Research Institute manual describes the western part of the western sandy plain as the Thar Desert and places the BWhw belt in west Jodhpur, Jaisalmer, Bikaner, Ganganagar, Hanumangarh, and western Churu. This core desert belt lies west of the Aravalli, where rainfall decreases from east to west; summer temperatures rise very high and fall rapidly at night. Thus, BWhw denotes the core western desert, not Rajasthan's adjoining semi-arid or monsoon zones.
Why the other options are wrong
- (A) Cwg is a monsoon climate with dry winters. In Rajasthan, it occurs in eastern and south-eastern areas, including parts of Udaipur, Chittorgarh, Kota, Baran, Jaipur, Alwar, Bharatpur, and Dholpur, not in the western Thar's core desert region.
- (C) Aw is the tropical savannah type with humid and dry conditions, associated with southern districts such as southern Udaipur, Dungarpur, Banswara, Pratapgarh, and Jhalawar; it does not describe Rajasthan's western desert.
- (D) BSh is the hot semi-arid steppe type. It receives more rainfall than the BWhw desert belt and belongs to the adjoining semi-arid transition belt, not the core hot-desert area.
Concept
RAS often asks about Rajasthan's climatic regionalisation under Koppen's classification, particularly the differences among hot-desert, semi-arid steppe, monsoon, and tropical-savannah zones. This classification connects rainfall and temperature patterns with vegetation, agriculture, desert ecology, and Rajasthan's physical geography.