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Climate & Soils

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Rajasthan Geography: Detailed Climate & Soils Analysis

[!IMPORTANT] Climatic Extremes: Rajasthan experiences the highest diurnal (day-night) and annual temperature ranges in India due to its continental location and sandy terrain.

1. Core Determinants of Rajasthan's Climate

Latitudinal Location: Situated mostly north of the Tropic of Cancer (23.5°N), falling in the sub-tropical/warm temperate zone (except Banswara/Dungarpur in the Torrid zone).
Distance from the Sea: The Arabian Sea is ~400 km away, minimizing any moderating oceanic influence (Continental Climate).
The Great Aravalli Divide: Functions inversely to the monsoon winds. The Arabian Sea branch travels parallel to it without shedding much rain. It also blocks the Bay of Bengal branch (Purvaiya) from crossing into the western Thar desert.

2. The Scientific Climatic Classifications (Highly Expected for RAS)

A. Koppen’s Classification (Based on Vegetation, Temp, & Rainfall)

Code	Climate Type (English)	Focus Districts / Regions	Annual Rainfall
BWhw	Arid / Hot Desert Climate	Jaisalmer, Bikaner, N-W Barmer	10 - 20 cm
BShw	Semi-Arid / Steppe Climate	Jodhpur, Nagaur, Pali, Jalore, Churu	20 - 40 cm
Cwg	Monsoon Type with Dry Winter	Jaipur, Alwar, Bharatpur, Tonk (Eastern Plains)	60 - 80 cm
Aw	Tropical Humid / Savanna	Banswara, Dungarpur, Jhalawar, Baran	80 - 100 cm

[!TIP] Exam Hack: If the question mentions "Savanna" (Aw), always look for the southern-most or south-eastern tip (Banswara/Jhalawar). If it mentions "Steppe" (BShw), look for the Luni basin or Shekhawati.

B. Thornthwaite’s Classification (Based on Evaporation & Moisture Index)

EA'd: Hot Arid (Extreme West: Jaisalmer, Barmer, W. Jodhpur).
DA'w: Semi-Arid / Sub-Humid (Largest area, covers most of central/eastern Rajasthan).
DB'w: Mixed Semi-Arid (Northern regions: Ganganagar, Hanumangarh, Bikaner).
CA'w: Sub-Humid (Southern regions: Banswara, Dungarpur, Jhalawar).

C. Trewartha’s Classification (Simplified Koppen based on Rainfall)

BWh: Extreme Arid (Jaisalmer).
BSh: Semi-Arid (Maximum area coverage).
Caw: Sub-Humid (Eastern Rajasthan).
Aw: Tropical Humid (South & South-East).

3. The Seasons & Crucial Terminology

Summer (Greeshma - March to mid-June):
- Loo (लू): Scorching, dry westerly winds blowing in May-June.
- Bhabhulya (भभूल्या): Localized mini dust-storms/whirlwinds caused by severe localized low pressure.
Monsoon (Varsha - Mid-June to September):
- Purvaiya (पुरवैया): Moisture-laden winds from the Bay of Bengal entering from the east.
- Dogra (डोगरा): Pre-monsoon showers occurring in late May/early June.
Winter (Sharad/Shit - November to February):
- Mawat / Golden Drops (मावट): Lifesaving winter rainfall caused by cyclonic Western Disturbances originating in the Mediterranean Sea. Extremely beneficial for Rabi crops (Wheat, Mustard).

4. Soil Classifications: Traditional vs USDA

A. USDA (Scientific) Soil Orders in Rajasthan

Soil Order	Characteristics & Dominant Regions
Aridisols	Dry, mineral soils found extensively in the Western Arid region (Churu, Jodhpur, Jaisalmer).
Entisols	Young soils with no distinct horizons. Includes sandy/dunes. Dominant in West (Barmer, Bikaner).
Alfisols	Mature, fertile alluvial soils. Found in the Eastern Plains (Jaipur, Alwar, Bharatpur).
Inceptisols	Very young soils found along the Aravalli slopes and southern foothills (Udaipur, Rajsamand).
Vertisols	Clay-rich, dark, self-ploughing black soils. Found in the Hadoti Plateau (Kota, Bundi, Jhalawar).

[!NOTE] Soil Problems:

Salinity/Alkalinity (Reh/Kallar): Common in canal-irrigated areas (Ganganagar) and Luni basin. Cured by adding Gypsum.

Water-logging (Sem Problem): Severe in IGNP areas (Hanumangarh). Cured by planting Safeda (Eucalyptus) and Gypsum.

Gully Erosion (अवनालिका): Severe in the Chambal basin causing Badlands (Bihads).