Climatic Characteristics and Classification of Rajasthan — Full Notes

Q: What are Western Disturbances? Explain their origin and agricultural significance for Rajasthan.

Western Disturbances are extratropical cyclones originating over the Mediterranean Sea, carried eastward by mid-latitude westerly jet streams. They bring winter rainfall (Mawat/Mahawat, 1–5 cm per event, 4–8 events per season) to northern Rajasthan — Ganganagar, Sikar, Jhunjhunu. This moisture is critical for rabi crops: wheat, mustard, and gram. Without Mawat, rabi yields decline sharply.

Climatic Characteristics and Classification of Rajasthan

Paper II

Unit 3

Reading Time 42 min read

1. Rajasthan has 4 climatic zones by rainfall: Western Desert (<10 cm), Semi-arid (10–50 cm), Sub-humid (50–100 cm), Humid (>100 cm).
2. Köpppen classification assigns 4 zones to Rajasthan: Aw (tropical savanna — southeast), BSh (hot semi-arid steppe), BWhw (hot desert), Cwg (humid subtropical — east).
3. Mt. Abu receives ~150 cm annual rainfall — highest in Rajasthan; Jaisalmer receives ~10 cm — lowest in India for a district headquarters.
4. State average annual rainfall: ~57 cm (compared to India's ~117 cm). 75–80% of rainfall concentrated in the SW monsoon season (July–September).
5. Phalodi (Jodhpur district) recorded India's all-time highest temperature of 51°C on May 19, 2016.
6. Western Disturbances (पश्चिमी विक्षोभ) bring winter rainfall (Mawat/Mahawat) to northern and western Rajasthan, critical for rabi crops (wheat, mustard).
7. SW monsoon reaches Rajasthan via two branches: Arabian Sea branch (enters via Gujarat, weaker) and Bay of Bengal branch (enters via Vindhyas, dominant).
8. Fatehpur-Sikar belt is the coldest zone in winter, recording sub-zero temperatures; Churu holds the record for both extremes in the same year.
9. Rajasthan has 5 distinct seasons: Summer (March–June), Pre-monsoon/Hot Dry (May–June), SW Monsoon (July–September), Post-monsoon/Retreating (October–November), Winter (December–February).
10. Drought frequency: Rajasthan experiences drought in approximately 3 out of every 10 years; western districts face drought risk in 6–8 out of 10 years. El Niño years strongly correlate with drought.
11. Aravalli range acts as a climatic divide: windward (eastern) side receives 60–100 cm rainfall; leeward (western) side receives <50 cm — the Thar extends where the Aravalli is low or absent.
12. Climate change impacts: Rising mean temperatures (+0.5°C over 50 years in Rajasthan), increased heat wave frequency, shifting monsoon onset, and accelerating desertification of the Thar.
13. Loo (लू) is the hot dry wind blowing from west to east in May–June, with temperatures reaching 45–50°C; causes heat strokes and crop damage.
14. Annual rainfall variability in Rajasthan is extremely high: co-efficient of variation (CV) exceeds 40% in the desert zone (compared to ~20% for India as a whole).
15. Monsoon onset in Rajasthan: Bay of Bengal branch reaches southeastern Rajasthan by late June; northwestern Rajasthan by mid-July; withdrawal begins in September from northwest. / मानसून आगमन: दक्षिण-पूर्वी राजस्थान में जून के अंत तक; उत्तर-पश्चिम में जुलाई मध्य तक; सितंबर में उत्तर-पश्चिम से वापसी शुरू। ---

CORE Key Points at a Glance

1
Rajasthan has 4 climatic zones by rainfall: Western Desert (<10 cm), Semi-arid (10–50 cm), Sub-humid (50–100 cm), Humid (>100 cm).
2
Köpppen classification assigns 4 zones to Rajasthan: Aw (tropical savanna — southeast), BSh (hot semi-arid steppe), BWhw (hot desert), Cwg (humid subtropical — east).
3
Mt. Abu receives ~150 cm annual rainfall — highest in Rajasthan; Jaisalmer receives ~10 cm — lowest in India for a district headquarters.
4
State average annual rainfall: ~57 cm (compared to India's ~117 cm). 75–80% of rainfall concentrated in the SW monsoon season (July–September).
5
Phalodi (Jodhpur district) recorded India's all-time highest temperature of 51°C on May 19, 2016.
6
Western Disturbances (पश्चिमी विक्षोभ) bring winter rainfall (Mawat/Mahawat) to northern and western Rajasthan, critical for rabi crops (wheat, mustard).
7
SW monsoon reaches Rajasthan via two branches: Arabian Sea branch (enters via Gujarat, weaker) and Bay of Bengal branch (enters via Vindhyas, dominant).
8
Fatehpur-Sikar belt is the coldest zone in winter, recording sub-zero temperatures; Churu holds the record for both extremes in the same year.
9
Rajasthan has 5 distinct seasons: Summer (March–June), Pre-monsoon/Hot Dry (May–June), SW Monsoon (July–September), Post-monsoon/Retreating (October–November), Winter (December–February).
10
Drought frequency: Rajasthan experiences drought in approximately 3 out of every 10 years; western districts face drought risk in 6–8 out of 10 years. El Niño years strongly correlate with drought.
11
Aravalli range acts as a climatic divide: windward (eastern) side receives 60–100 cm rainfall; leeward (western) side receives <50 cm — the Thar extends where the Aravalli is low or absent.
12
Climate change impacts: Rising mean temperatures (+0.5°C over 50 years in Rajasthan), increased heat wave frequency, shifting monsoon onset, and accelerating desertification of the Thar.
13
Loo (लू) is the hot dry wind blowing from west to east in May–June, with temperatures reaching 45–50°C; causes heat strokes and crop damage.
14
Annual rainfall variability in Rajasthan is extremely high: co-efficient of variation (CV) exceeds 40% in the desert zone (compared to ~20% for India as a whole).
15
Monsoon onset in Rajasthan: Bay of Bengal branch reaches southeastern Rajasthan by late June; northwestern Rajasthan by mid-July; withdrawal begins in September from northwest. / मानसून आगमन: दक्षिण-पूर्वी राजस्थान में जून के अंत तक; उत्तर-पश्चिम में जुलाई मध्य तक; सितंबर में उत्तर-पश्चिम से वापसी शुरू।

PREDICTED Predicted RAS Questions

Based on PYQ trends and 2026 syllabus analysis

1 5M What are Western Disturbances? Explain their origin and agricultural significance for Rajasthan. 5 marks · 50 words

Model Answer

Western Disturbances are extratropical cyclones originating over the Mediterranean Sea, carried eastward by mid-latitude westerly jet streams. They bring winter rainfall (Mawat/Mahawat, 1–5 cm per event, 4–8 events per season) to northern Rajasthan — Ganganagar, Sikar, Jhunjhunu. This moisture is critical for rabi crops: wheat, mustard, and gram. Without Mawat, rabi yields decline sharply.

~50 words • 5 marks

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CORE Key Points at a Glance

PREDICTED Predicted RAS Questions