Chapter - 4
Climate
️ Weather and Climate :-
Weather is a transient state of the atmosphere , whereas climate refers to the average of weather conditions over a relatively long period of time . The weather changes quickly, such as in a day or a week, but the change in climate occurs in 50 or more years .
️ Factors affecting Indian weather :-
- Surface distribution of air pressure and heat.
- Upper air circulation, inflow of air masses.
- Rain-bringing systems – Western Disturbances and Tropical Cyclones.
Main features of Indian monsoon :-
Change in the direction of the wind according to the season; Monsoon winds are uncertain and irregular (suspected).
To provide wide uniformity to the Indian climate despite the variation in the regional nature of monsoon winds.
️ Factors affecting the climate of India :-
India extends north of the equator. The Tropic of Cancer passes almost through it, the Himalayan mountain range surrounds it in the north and the Indian Ocean in the south. These conditions affect the climate here in the following way:-
Latitude:- The southern part of India lies between the equator and the Tropic of Cancer. Therefore, there is a tropical effect here, while the north part of the Tropic of Cancer falls in the temperate zone.
Mountain range: - The Himalayan mountain range located in the north of India prevents the cold winds coming from the North Pole from coming into India, due to which the climate in the Indian subcontinent remains equitable. This mountain range helps in raining by stopping the monsoon winds.
The distribution of water and land:- The peninsular part of India being surrounded by the Bay of Bengal on one side and the Arabian Sea on the other affects the climate here, due to which the south-west winds help to absorb moisture.
The northern part of India is landlocked, so the temperature here becomes very high in summer and very low in winter.
Apart from this, the distance from the coast, height above sea level and relief also affect the climate.
️ Traditional Seasons of India :-
The traditional seasons of India are made on a bi-monthly basis, so their number is 6. Their names are – Basant, March – April, Summer: May – June, Rain: July – August, Sharad: September – October, Hemant: November – December and Shishir: January – February .
According to Koppen, the climatic regions of India :-
According to Koppen the following are the climatic regions of India :-
Monsoon type of short dry season (Amw) :- This type of climate along the west coast.
Dry monsoon type in summer (As):- The region with this type of climate is spread along the Coramandal coast.
Tropical savanna type climate (Aw): - This type of climate is found in almost the entire peninsular India except some areas of the coastal region.
Semi- arid steppe climate (BShw): - Found in the interior of the peninsula and in some parts of Gujarat, Rajasthan, Haryana, Punjab, Jammu and Kashmir.
Warm desert type climate (BWhw): - This type of climate is found only in the western part of Rajasthan.
Dry winter region (Cwg): - This climate is found in most of the northern plains of India.
Cold wet winter region (Dfc): - This climate is found in the eastern region.
Polar climate (E): - This type of climate is found in Kashmir and nearby mountain ranges.
️ Intratropical Convergence Zone (ITCZ) :-
The Inter-Tropical Convergence Zone is a low pressure area located at the equator. In this region, the trade winds come from the opposite direction and as a result the wind starts rising.
ITC in the month of July. Jade gets situated in the Gangetic plain around 20° to 25° north latitude. It is also called monsoon trough. This monsoon trough encourages the development of thermal low air over north and north-west India.
The trade winds of the southern hemisphere cross the equator between 40° and 60° east longitudes due to the northward movement of the ITCZ.
Under the influence of the Coriolis force, the direction of these trade winds crossing the equator becomes from south-west to north-east. This is the South-West monsoon. In winter, ITCZ shifts to the south and the direction of the winds also changes from south-west to north-east, this is the north-east monsoon.
El Ni No: -
El-Nino literally means 'Child Christ/Isa'. This is the term used for a meteorological phenomenon. Which usually happens in the month of December near the Peruvian coast around Christmas.
In this, the Peruvian ocean current, which is also called Humboldt current. Its water becomes relatively hot. The effect of this event is seen on the climate of the world, somewhere there are droughts and somewhere there are floods i.e. unexpected events come to the fore. Its effect is also seen on the climate of India.
️ Monsoon :-
The word is derived from the Arabic language. The word monsoon means change in the direction of the winds according to the seasons.
️ Monsoon Blast :-
When the moisture laden winds become extremely heavy, they release their surplus moisture with great thunder. Which reaches the ground in the form of torrential rain. These rains are so heavy that they flood a wide area in a few hours. Heavy rainfall starts suddenly by the Southwest Monsoon. This natural phenomenon is called monsoon eruption.
️ Monsoon break :-
When the monsoon winds fail to bring rain for two weeks or more, there is a dry period in the rainy season, it is called monsoon break. This is either due to the weakening of tropical cyclones or a change in the status of the Inter-Tropical Convergence Zone in India. The inversion of temperature in western Rajasthan prevents the rise of water laden with water vapor and there is no rainfall.
व Monsoon discharge: -
Withdrawal or withdrawal of monsoon is called withdrawal of monsoon. From the beginning of September, the monsoon starts withdrawing from North-West India and by mid-October it withdraws from the rest of India except South India. The returning monsoon winds pick up water vapor from the Bay of Bengal and bring rain to Tamil Nadu in the form of the North-East Monsoon.
️ Understanding Monsoon :-
The nature and composition of monsoon is understood on the basis of meteorological data collected from land, oceans and upper atmosphere in different parts of the world. The air pressure found between Tahiti in French Polynesia (approximately 180 D and 1490 W) in the eastern Pacific Ocean and Port Darwin in the Indian Ocean east of Australia (12 ° 30' D and 131 ° E). The intensity of monsoon can be predicted by measuring the difference of The India Meteorological Department makes long-term forecasts about the likely behavior of the monsoon on the basis of 16 factors (parameters).
️ Seasons in India according to the Indian Meteorological Department :-
According to the Indian Meteorological Department, there are generally four seasons in India. Which are as follows:-
- winter season
- summer season
- south-west monsoon season
- Monsoon retreat
️ Mechanism of weather in summer :-
Surface air pressure and winds: -
At the beginning of the summer season, when the Sun enters the Uttarayan position, there is a reversal in air circulation in both the lower and higher levels of the subcontinent.
By mid-July, the low pressure belt near the surface called the Inter-Tropical Convergence Zone (ITCZ) shifts north and is located approximately parallel to the Himalayas at 20° to 25° north latitude. She goes .
Jet – Flow :-
At an altitude of about 12 km above the earth's surface, the air currents moving in a horizontal direction in the troposphere are called jet air flow. This jet stream does the work of bringing western disturbances to India in winter. These disturbances enter India only because of the change in the position of the jet stream. Similarly, the eastern jet-flow attracts tropical cyclones towards India.
️ Mechanism of weather in winter :-
Surface air pressure and winds: -
The weather of India in winter is influenced by the distribution of air pressure in Central and West Asia. At this time, a high pressure center is established over Tibet to the north of the Himalayas. To the south of this high pressure center, the flow of winds starts along with the land at low level towards the Indian subcontinent.
The surface winds that move outward from the high pressure center of Central Asia reach India in the form of dry continental winds. These continental winds come in contact with the trade winds in North-West India. But the status of this contact area is not permanent.
️ The season of withdrawal of monsoon ie the return of monsoon :-
By the second week of September, the south-west monsoon starts returning from northern India and returns from the south by mid-October and early December. Unlike the southerly eruption, the withdrawal of monsoon winds is quite gradual.
With the return of monsoon winds, the sky becomes clear. The day temperature rises slightly but the nights become pleasant. The daily temperature difference becomes high in this season. The cyclones originating in the Bay of Bengal move from southeast to north-west and bring substantial rainfall.
