Climate India Flashcards
Factors Affecting India’s Climate
Latitude: India lies between 8°4’N and 37°6’N, so the Tropic of Cancer divides the country into tropical and subtropical zones. Altitude: The Himalayas block cold Central Asian winds, keeping northern India warmer in winter. Distance from the Sea: Coastal regions (e.g., Mumbai, Chennai) have a moderate climate, while inland areas (e.g., Delhi) face extreme temperatures. Pressure & Winds: The Indian climate is influenced by pressure belts, the ITCZ, and monsoonal winds.
Mechanism of Monsoons
The monsoon is caused by differential heating and cooling of land and sea. In summer, low pressure over the Indian subcontinent attracts moisture-laden winds from the Indian Ocean. The reversal of winds in winter leads to dry, cold winds blowing from land to sea. The ITCZ shifts northward in summer, aiding monsoon onset.
Jet Streams & Monsoons
Westerly Jet Stream: Influences winter weather, brings western disturbances. Easterly Jet Stream: Helps the onset of the summer monsoon. Jet streams control pressure systems, affecting rainfall patterns.
Monsoon Onset & Withdrawal
The monsoon typically hits Kerala around June 1st. It advances northward in phases, reaching most parts of India by mid-July. Withdrawal starts in September from the northwest and is complete by mid-October. This process affects the cropping cycle (Kharif & Rabi seasons).
Climatic Regions of India (Köppen’s Classification)
- Tropical Wet (Am): Western Ghats, NE India. 2. Tropical Wet & Dry (Aw): Central and Peninsular India. 3. Hot Desert (BWh): Rajasthan, Kutch. 4. Semi-Arid (BSh): Deccan Plateau, parts of Gujarat. 5. Humid Subtropical (Cwa): Northern plains, foothills of Himalayas. 6. Mountain (H): Himalayan region. Understanding these regions helps link climate to vegetation, agriculture, and population distribution.
El Niño, La Niña & Monsoons
El Niño: Warms Pacific Ocean, weakens monsoon, causes droughts in India. La Niña: Cools Pacific Ocean, strengthens monsoon, leads to excess rainfall. ENSO cycles are closely linked to monsoon variability and are crucial for predicting droughts and floods.
Loo
Type: Hot, dry summer wind. Region: Northern Plains (Punjab, Haryana, Delhi, Uttar Pradesh). Season: Pre-monsoon (April–June). Impact: Raises temperatures above 45°C, causes heatwaves, can lead to dehydration and sunstrokes.
Kalbaisakhi (Nor’westers)
Type: Sudden, violent thunderstorms. Region: West Bengal, Assam, Odisha, Bihar. Season: Pre-monsoon (March–May). Impact: Brings heavy rain, lightning, and hail; helps wheat and jute crops but can damage property and lives.
Mango Showers
Type: Pre-monsoon rainfall. Region: Kerala, Karnataka, coastal Andhra Pradesh. Season: April–May. Impact: Helps ripen mangoes and coffee crops, reduces heat before monsoon onset.
Western Disturbances
Type: Extra-tropical cyclones. Origin: Mediterranean region. Region: North and Northwest India. Season: Winter (Dec–Feb). Impact: Brings rainfall and snowfall to Himalayas, vital for rabi crops like wheat, but can also cause cold waves and fog.
Blossom Showers
Type: Pre-monsoon rainfall. Region: Kerala, Karnataka. Season: Spring (April). Impact: Aids in flowering of coffee plants, beneficial for spice crops.
Kathabaisakhi
Type: Local storm. Region: Odisha, West Bengal. Season: Pre-monsoon (April–May). Impact: Brings heavy rain and lightning, similar to Kalbaisakhi, but more intense in Odisha.
October Heat
Type: Hot, dry post-monsoon winds. Region: Most of India, especially central and southern regions. Season: Post-monsoon (Oct). Impact: High humidity and temperatures, causes discomfort, but fades as northeast monsoon sets in.
Trade Winds
Type: Steady, persistent winds. Region: Entire Indian Peninsula. Season: Throughout the year (most impactful during monsoon). Impact: Help drive the southwest monsoon, bringing rain to most of India.
Vasant Ritu (Spring)
Months: March–April Hindu Calendar: Chaitra, Vaishakha Features: Pleasant weather, blooming flowers, moderate temperatures. Cultural Significance: Celebrated with festivals like Holi and Vasant Panchami.
Grishma Ritu (Summer)
Months: May–June Hindu Calendar: Jyeshtha, Ashadha Features: High temperatures, dry conditions, occurrence of hot winds (Loo). Impact: Water scarcity in many regions; mangoes and summer crops grow.
Varsha Ritu (Monsoon)
Months: July–August Hindu Calendar: Shravana, Bhadrapada Features: Heavy rainfall due to southwest monsoon winds, high humidity. Impact: Essential for agriculture (Kharif crops), but can cause floods in low-lying areas.
Sharad Ritu (Autumn)
Months: September–October Hindu Calendar: Ashwin, Kartika Features: Clear skies, retreating monsoon, cooler evenings. Cultural Significance: Festivals like Navratri and Diwali are celebrated during this season.
Hemant Ritu (Pre-winter)
Months: November–December Hindu Calendar: Margashirsha, Pausha Features: Mild cold, dry weather, shorter days. Impact: Ideal for rabi crop sowing; pleasant weather for outdoor activities.
Shishir Ritu (Winter)
Months: January–February Hindu Calendar: Magha, Phalguna Features: Cold temperatures, fog in northern India, dry air. Impact: Affects travel and agriculture; important for crops like wheat and mustard.
Indian Calendar System
Hindu Lunar Calendar: Based on moon cycles, months start with new moon or full moon. Saka Era: Official calendar of India (begins in 78 AD). Months: Chaitra (Mar-Apr), Vaishakha (Apr-May), Jyeshtha (May-Jun), Ashadha (Jun-Jul), Shravana (Jul-Aug), Bhadrapada (Aug-Sep), Ashwin (Sep-Oct), Kartika (Oct-Nov), Margashirsha (Nov-Dec), Pausha (Dec-Jan), Magha (Jan-Feb), Phalguna (Feb-Mar). Importance: Tied to agricultural cycles, religious festivals, and cultural events.
Highest Rainfall in India
Location: Mawsynram, Meghalaya Average Annual Rainfall: ~11,871 mm (World’s Wettest Place) Reason for High Rainfall: Orographic rainfall caused by the Bay of Bengal branch of the southwest monsoon hitting the Khasi Hills. Nearby Wettest Spot: Cherrapunji (~11,777 mm). Impact: Lush greenery, biodiversity hotspot, unique living root bridges, but also frequent landslides and waterlogging issues.
Arakan Hills and Indian Monsoon
Location: Western Myanmar (close to northeast India). Geographical Role: Acts as an orographic barrier for monsoon winds. Impact on Monsoon: The southwest monsoon winds from the Bay of Bengal hit the Arakan Hills, get deflected northward, and turn towards northeastern India, intensifying rainfall in states like Meghalaya (e.g., Mawsynram, Cherrapunji). Key Mechanism: Orographic uplift causes heavy rainfall on the windward side, while the deflection of winds contributes to extreme rainfall in northeastern India. Significance: The hills are a crucial factor in creating one of the rainiest regions in the world and influencing India’s overall monsoon pattern.
