Introduction to Indian Weather Seasons:

India experiences a rhythmic annual climate cycle with four distinct seasons: cold weather, hot weather, southwest monsoon, and retreating monsoon.

How does the Indian Weather Seasons Shape Winter Climate Dynamics in Northern and Peninsular India?

Temperature Dynamics in Indian weather seasons: 

• Winter Climate Dynamics in Northern and Peninsular India during the Indian weather seasons: Usually, the cold weather season sets in by mid-November in northern India. 
  • The mean daily temperature remains below 21°C over most parts of northern India. 

Mean Monthly Temperatures of the Day in January

• Cold Experiences in Northern India’s:  Especially in regions like Punjab, Haryana, and Rajasthan, can be very cold, with temperatures sometimes dropping below freezing. 
• This cold is attributed to three reasons:
  • Continental Climes: States like Punjab, Haryana, and Rajasthan are far away from the moderating influence of sea and experience continental climate.
  • Himalayan Influence: The snowfall in the nearby Himalayan ranges creates a cold wave situation and
    • Around February, the cold winds coming from the Caspian Sea and Turkmenistan bring cold waves along with frost and fog over the north-western parts of India.
  • Moderating Seas in Indian climate: In contrast, the Peninsular region doesn’t experience a sharp cold season due to the sea’s moderating influence and its equatorial proximity. 
    • Thus, coastal regions, like Thiruvanantapuram, maintain a mild temperature range throughout the year.

Pressure and Surface Winds (January)

Pressure and Wind Patterns during the Solstice in India:

• Winter Solstice: Sun’s Dance Over the Tropic of Capricorn: By the end of December (22nd December), the sun shines vertically over the Tropic of Capricorn in the southern hemisphere. 
• Winter Pressure Patterns and Wind Dynamics in India: During winter, high-pressure conditions dominate northern India, while the south has slightly lower pressure. 
  • The isobars of 1019 mb and 1013 mb pass through northwest India and the far south, respectively.
  • Winds, driven by these pressure differences, move from the northwestern high-pressure zone to the southern low-pressure areas. (Refer Figure)

Rainfall Exceptions and Northeast Dynamics in India:

• Winter Monsoons: The Quiet Season in India’s Rainfall Symphony: Generally, winter monsoons don’t bring rain to India, primarily because of their low humidity and the land’s anti-cyclonic circulation. 
• However, there are exceptions:
  • Mediterranean Influence: Weak temperate cyclones from the Mediterranean can cause rainfall in northwestern India, 
  • North-eastern regions like Arunachal Pradesh and Assam experience 25-50 mm of rain during the winter.
  • Northeast Monsoon Dynamics: The northeast monsoon, after collecting moisture over the Bay of Bengal, results in heavy rainfall along the Tamil Nadu coast and nearby south-eastern regions in October and November.

 India: Mean Monthly Temperature of the Day in July

Indian Weather Seasons: Embracing the Heat in the Hot Weather Season

Temperature Dynamics:

• Summer’s Arrival: Northern India’s Temperature Surge : As the sun moves northward from March, northern India witnesses rising temperatures, marking the onset of summer, which spans April, May, and June. (Refer Figure)
  • Temperatures typically range between 30°C to 32°C. By May, northwestern regions like Gujarat and Madhya Pradesh often experience scorching temperatures up to 48°C.
• Gentle Summers in Southern Part: In contrast, southern India enjoys a milder summer, with temperatures maintained between 26°C and 32°C, due to its peninsular location and the oceans’ moderating effects. 
• Consistent Coastal Climes: Coastal regions see minimal temperature variation from north to south, and the mean daily minimum during these summer months rarely falls below 26°C.

Pressure and Wind Patterns in Northern India:

• Summer’s Grip: Intense Heat and Atmospheric Shifts : Summer brings intense heat and falling air pressure to northern India. 
• Northward Movement of the ITCZ: Shaping Monsoon Troughs and Low-Pressure Dynamics: The ITCZ, influenced by the subcontinent’s heat, shifts northward by July, centering around 25°N. 
  • This change creates a low-pressure monsoon trough stretching from the Thar desert to the Chotanagpur plateau. 
• Loo’ Hot Winds and Dust Storms Ballet in Northern India: During summer afternoons, hot winds called ‘Loo’ blow, especially in the ITCZ’s heart. 
  • Dust storms are frequent in May across regions like Punjab, Haryana, and Uttar Pradesh, offering brief relief from the intense heat with their accompanying light rains. 
• Clash of Air Masses: Intense Storms and Weather Turmoil in Northern India: Occasionally, the clash between dry and moist air masses results in intense local storms, characterised by strong winds, heavy rains, and even hailstorms.

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