Introduction The natural environment is made of landforms and drainage systems and atmospheric conditions. Some atmospheric conditions cause heat and discomfort and others may be cool, windy, bright or wet. The atmospheric conditions are dictated by various parameters like geographic location of an area, or month of the year.
Weather refers to the state of the atmosphere over an area at any point of time. Weather conditions may fluctuate often. Climate refers to the sum total of weather conditions and variations over a large area for a long period of time (over 30 years). The elements of weather and climate are: temperature, atmospheric pressure, wind, humidity and precipitation.
On the basis of the generalised monthly atmospheric conditions, the year is divided into seasons such as winter, summer or rainy seasons. The world is divided into climatic regions, which may vary from region to region and also from one season to another.
Climatic conditions in India:
In India, we have the ‘monsoon’ type of climate which refers to the seasonal reversal in the wind direction during a year.
South and the southeast parts of Asia generally have this type of climate.
Despite an overall unity in the general pattern, there are perceptible regional variations in climatic conditions within the country.
In summer, the temperature rises up to 50°C in some parts of the Rajasthan desert, whereas it may be around 20°C in Pahalgam in Jammu and Kashmir.
Drass in Jammu and Kashmir experiences temperatures as low as minus 45°C on a winter night. On the other hand, at the same time the temperature at Thiruvananthapuram may be around 22°C.
In certain places there is a wide difference even between day and night temperatures. In the Thar Desert the day temperature may rise to 50°C, and drop down to 15°C the same night.
Areas like Meghalaya have an annual precipitation of over 400 cm whereas it is only 10 cm in Ladakh and western Rajasthan.
Most parts of the country receive rainfall from June to September. But the Tamil Nadu coast gets a large portion of its rain during October and November.
There is decrease in rainfall generally from east to west in the Northern Plains.
These variations have given rise to variety in lives of people – in terms of the food they eat, the clothes they wear and also the kind of houses they live in.
Climatic Controls
Climate is controlled by six major factors. They are:
Latitude: The solar energy varies according to latitude at different parts of the earth due to its curvature. Due to this, air temperature decreases from equator to the poles.
Altitude: The density of the atmosphere is less at higher altitudes and the temperature also decreases.
Pressure and wind system: This depends on the latitude and altitude of the place and influences temperature and rainfall patterns.
Distance from the sea: The sea moderates the climate. People who stay far away from the sea experience extreme weather conditions, like extremely hot summers and cold winters. Such extreme weather conditions are known as continentality.
Ocean currents: Ocean currents along with onshore winds affect the climate of coastal areas.
Relief features: The sheltered side of mountains are drier. This is because high mountains act as barriers for hot or cold winds and may cause precipitation if they lie in the path of rain bearing winds.
Factors Affecting India’s climate
Latitude
India’s climate has characteristics of tropical as well as subtropical climates.
The Tropic of Cancer runs through the middle of the country from the Rann of Kuchchh to Mizoram.
The areas lying to the south of the Tropic of Cancer belong to the tropical area while the other areas lie in the subtropics.
Altitude
The average elevation in the coastal areas of India is about 30 meters, whereas the average elevation in the mountains in the north is about 6,000 meters.
So, the Himalayas act like a barrier that prevents the cold winds of Central Asia to enter the Indian subcontinent.
That is why the Indian subcontinent gets comparatively milder winters as compared to Central Asia.
Pressure and wind
Major atmospheric conditions that govern the Indian climate and its associated weather conditions are:
Pressure & surface winds;
Upper air circulation;
Western Cyclonic disturbances; and
Tropical cyclones.
The Indian subcontinent lies in the region of north-easterly winds.
These winds originate from the subtropical high-pressure belt of the northern hemisphere and blow towards south.
They get deflected to the right due to the Coriolis force and then move towards the low pressure area near the equator.
Coriolis force: An apparent force caused by the earth’s rotation. The Coriolis force is responsible for deflecting winds towards the right in the northern hemisphere and towards the left in the southern hemisphere. This is also known as ‘Ferrel’s Law’. Remaining in comment
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