- India's climate closely mirrors that of a tropical country, despite its northern part (north of the Tropic of Cancer) being situated in the temperate belt.
- The Indian subcontinent is geographically separated from the rest of Asia by the towering Himalayan ranges, which act as a barrier, obstructing the southward movement of cold air masses from Central Asia.
- During winters, the northern half of India experiences temperatures that are 3°C to 8°C warmer than other areas at similar latitudes.
- In contrast, during the summer season, the sun's overhead position results in the climate in southern parts resembling an equatorial dry climate.
- The plains in North India are influenced by a hot dry wind known as 'loo,' blowing from the Thar, Baloch, and Iranian Deserts.
- This wind elevates temperatures to levels comparable to those in the southern parts of the country.
- Consequently, the entirety of India, situated south of the Himalayas, can be climatically classified as a tropical country.
India experiences a distinctive tropical monsoon climate, characterized by the seasonal reversal of winds in the Arabian Sea and Bay of Bengal. This climatic pattern creates a pronounced wet and dry season, making India's climate more accurately classified as tropical monsoon type rather than solely tropical or partially temperate.
Features of Indian Climate:
Regional Climatic Diversity: India exhibits high climatic diversity due to its varied topography, including factors like location, altitude, distance from the sea, and relief.
Rainfall:
- Distinct Wet and Dry Seasons: Most regions experience clear distinctions between wet and dry seasons. However, places like the Thar Desert and Ladakh have no wet season.
- Variability in Annual Rainfall: Mean annual rainfall varies significantly across the country. For instance, Mawsynram and Cherrapunji in Meghalaya receive approximately 1,000 cm of annual rainfall, while Jaisalmer rarely exceeds 12 cm.
- Regional Contrasts: The Ganga delta and coastal plains of Odisha witness intense rainfall in July and August, whereas the Coromandel Coast experiences dry conditions during these months.
- Monsoon Onset Differences: Places like Goa, Hyderabad, and Patna receive southwest monsoon rains by the first quarter of June, while Northwestern India awaits rains until early July.
Temperature:
- Diurnal and Annual Variations: Significant diurnal (daily) and annual temperature variations are observed.
- Extreme Ranges: The Thar Desert experiences the highest diurnal temperature ranges, while the Himalayan regions record the highest annual temperature ranges.
- Coastal Moderation: Coastal regions exhibit comparatively lower diurnal and mean annual temperature ranges.
- Temperature Extremes: In December, temperatures can drop to -40°C in some places in Jammu and Kashmir, while coastal regions maintain average temperatures of 20-25°C.
- Seasonal Extremes: Winters are moderately cold across most regions, while summers can be extremely hot.
- Himalayan Contrasts: The Himalayan regions face harsh winters but enjoy moderate summers.
The combination of these factors contributes to the unique and diverse climate experienced across different parts of India.
Factors Affecting the Climate of India
Factors Related to Location and Relief
Latitude:
- The Tropic of Cancer runs through the central part of India, creating a subtropical and temperate zone in the north and a tropical zone in the south.
- The tropical zone experiences consistently high temperatures throughout the year.
Himalayan Mountains:
- Act as a climatic divide, protecting the subcontinent from cold northern winds.
- Trap monsoon winds, compelling them to disperse moisture across India.
Distribution of Land and Water:
- Surrounded by the Indian Ocean on three sides, creating differential heating between land and sea.
- Coastal areas experience a more moderate climate, while interior regions face climate extremes.
Distance from the Sea:
- Coastal areas with long coastlines exhibit an equable climate.
- Inland areas lack the moderating influence of the sea, leading to climate extremes.
Altitude:
- Temperature decreases with higher altitude.
- Mountainous areas are cooler due to thin air, showcasing variations like Agra at 16°C in January compared to Darjeeling at 4°C.
Relief:
- Physiography influences temperature, air pressure, wind patterns, and rainfall distribution.
- Windward sides of the Western Ghats and Assam receive more rainfall during the monsoon, while leeward areas remain dry.
Factors Related to Air Pressure and Wind
Surface Pressure and Winds (Winter Season):
- High-pressure center north of the Himalayas causes dry continental air mass from the north.
- Collisions with trade winds in northwestern India lead to variable contact zones, affecting wind patterns.
Jet Stream and Upper Air Circulation:
- Westerly winds blow over Asia, parallel to the Tibetan highlands, creating jet streams.
- Tibetan highlands act as a barrier, causing jet streams to split.
- Southern branch influences India's winter weather.
Western Cyclonic Disturbance and Tropical Cyclones:
- Westerly jet stream brings cyclonic disturbances from the west and northwest during winter.
- Tropical cyclones form over the Indian Ocean and Bay of Bengal, impacting coastal regions.
Inter-Tropical Convergence Zone (ITCZ) and Southwest Monsoon (Summer Season):
- ITCZ shifts northward, attracting winds from all directions, initiating the southwest monsoon.
- Easterly jet stream influences the monsoon trough, causing a reversal of winds from northeast to south and southwest.
Jet Streams and Upper Air Circulation (Summer Season):
- Easterly jet stream in June, moving over the Peninsula, influences monsoon patterns.
- Tropical depressions guided by the easterly jet stream impact the distribution of monsoon rainfall.
- Understanding these factors provides insights into India's diverse climates during different seasons, shaping its unique meteorological characteristics.
FAQs - India's Climate and Factors Influencing It
1. Why is India's climate often referred to as tropical, despite its northern part being in the temperate belt?
Ans. India's tropical climate is primarily due to its location south of the Tropic of Cancer, which creates high temperatures. The temperate influences are mitigated by geographical barriers, such as the Himalayas, blocking cold air from Central Asia.
2. What role do the Himalayan Mountains play in India's climate?
Ans. The Himalayas act as a climatic divide, shielding India from cold northern winds. They also trap monsoon winds, ensuring the dispersion of moisture across the subcontinent.
3. How do seasons affect temperatures in different parts of India?
Ans. During winters, the northern half experiences temperatures 3°C to 8°C warmer than similar latitudes. In summers, the sun's position results in southern parts resembling an equatorial dry climate.
4. What is the 'loo,' and how does it impact North India's climate?
Ans. The 'loo' is a hot dry wind blowing from the Thar, Baloch, and Iranian Deserts. It raises temperatures in North India, making them comparable to the southern parts of the country.
5. How would you classify India's climate?
Ans. India's climate is best classified as a tropical monsoon type due to the seasonal reversal of winds in the Arabian Sea and Bay of Bengal, resulting in distinct wet and dry seasons.
6. What contributes to India's climatic diversity?
Ans. India's diverse topography, including factors like location, altitude, distance from the sea, and relief, contributes to its high regional climatic diversity.
7. Why do coastal areas in India have a more equable climate?
Ans. Coastal areas exhibit a more moderate climate due to their long coastlines, benefiting from the sea's moderating influence. In contrast, inland areas experience climate extremes.
8. How does altitude impact temperature in India?
Ans. Temperature decreases with higher altitude. Mountainous areas are cooler due to thin air, resulting in variations such as Agra experiencing higher temperatures compared to Darjeeling.
9. What factors contribute to the variability in India's annual rainfall?
Ans. The distribution of land and water, distance from the sea, and the influence of relief play significant roles in the variability of annual rainfall across different regions in India.
10. How do jet streams influence India's climate during different seasons?
Ans. Jet streams, especially the westerly and easterly ones, play crucial roles in India's weather patterns, influencing the movement of cyclonic disturbances, tropical cyclones, and the onset of monsoons.
