Before you know about the climate of India, you must know what is climate and the meaning of climate. Climate has a different meaning in different conditions. In Cambridge Dictionary you can find different meanings about climate. According to the Cambridge dictionary, Climate means the general weather conditions usually found in a particular place for a very long period of time of more than thirty years.
Climate is different from weather. Weather refers to the state of the atmosphere over an area at any given period of time. Weather can change throughout the day but the climate of a country is the same for many years.
The climate of India is a monsoon type. This type of climate is found in south and southeast Asia. There are variations in climatic conditions in India. The coastal regions of India show the least amount of difference between the temperatures of night and day. In the interior regions, the difference in temperatures of day and night is huge.
There are different factors which are affecting the climate of India. These are briefly given below:
The factors affecting the climate of India
Climate of India is affected by the various factors which are controls the variations in temperature in the Indian climate. The factors are divided into six types, namely:
- Distance from the Sea
- Monsoon Wind
- Jet Streams
India lies between 8°4’N and 37°6’N latitudes. The Tropic of Cancer divides the country into two equal halves. The area located to the south of Tropic of cancer experiences high temperature and no severe cold season throughout the year whereas, the areas to the north of this parallel enjoy a subtropical climate. Here, summer temperature may rise above 40°C and it is close to freezing point during winter.
When the altitude increases, The temperatures decreases. Temperature decreases at the rate of 6.50C for every 1000 meters of ascent. It is called the normal lapse rate.
Places in the mountains are cooler than the places on the plains. The places located at higher altitudes even in south India have a cool climate.
Ooty and several other hill stations of South India and of the Himalayan ranges like Mussourie, Shimla, etc., are much cooler than the places located on the Great Plains.
Distance from the Sea
Distance from the sea does not cause only temperature and pressure variations but also affects the amount of rainfall. A large area of India, especially the peninsular region, is not very far from the sea and this entire area has a clear maritime influence on climate. This part of the country does not have a very clearly marked winter and the temperature is equable almost throughout the year.
Areas of central and north India have much seasonal variation in temperature due to the absence of influence of seas. Here, summers are hot and winters are cold. The temperature at Kochi does not exceed 30°C as its location is on the coast while it is as high as 40°C at Delhi, since it is located in the interior part.
Air near the coast has more moisture and greater potential to produce precipitation. Due to this fact, the amount of rainfall at Kolkata located near the coast is 119 cm and it decreases to just 24 cm at Bikaner which is located in the interior part.
Monsoon winds are the most dominant factor which affects the climate of India. These are seasonal reversal winds.
India remains in the influence of these winds for a considerable part of a year. The sun’s rays are vertical over the central part of India during the mid-June, the summer season ends in India by the end of May. It is because the sunset of southwest monsoon brings down the temperature of the entire India and causes moderate to heavy rainfall in many parts of the country. Similarly, the climate of southeast India is also influenced by northeast monsoon.
Relief of India has a great bearing on major elements of climate such as temperature, atmospheric pressure, direction of winds and the amount of rainfall.
The Himalayas acts as a barrier to the freezing cold wind blows from central Asia and keep the Indian subcontinent warm. As such the north India experiences tropical climate even during winter.
During the southwest monsoon, areas on the western slope of the Western Ghats receive heavy rainfall. On the contrary, vast areas of Maharashtra, Karnataka, Telangana, Andhra Pradesh, and Tamilnadu lie in rain shadow or leeward side of the Western Ghats receive very little rainfall.
Jet streams are the fast-moving winds blowing in a narrow zone in the upper atmosphere. According to the Jet stream theory, the onset of southwest monsoon is driven by the shift of the sub-tropical westerly jet from the plains of India towards the Tibetan plateau.
The easterly jet streams cause tropical depressions both during southwest monsoon and retreating monsoon.
Monsoon of India
The word ‘monsoon’ has been derived from the Arabic word ‘Mausim’ which means ‘season’. It blows from the south-west to north-east during summer and from the north-east to south-west during winter.
Monsoons are a complex meteorological phenomenon. According to the Dynamic concept, Monsoon wind originates due to the seasonal migration of planetary winds and pressure belts following the position of the sun.
During the summer solstice, the sun’s rays fall vertically over the Tropic of cancer. Therefore, all the pressure and wind belts of the globe shift northwards.
At this time, Inter -Tropical Convergence Zone (ITCZ) also moves northward, and a major part of Indian landmass comes under the influence of southeast trade winds. While crossing equator this wind gets deflected and takes the direction of southwest and becomes southwest monsoon.
During the winter season, the pressure and wind belts shift southward, thereby establishing the north-east monsoon over this region. Such systematic change in the direction of planetary winds is known as monsoon.
Seasons of India
The India Meteorological Department (IMD) recognised 4 seasons in India.
- The cold weather season (Winter)
- The hot weather season (Summer)
- Monsoon season (Rainy)
- Post monsoon season (Autumn)
The Cold weather season(Winter)
The Cold weather season also known as winter season. The vertical rays of the sun fall over tropic of Capricorn which is far away from India during this period. India receives the slanting sun’s rays which results in low temperature.
The cold weather season is characterised by clear skies, fine weather, light northerly winds, low humidity and large day time variations of temperature. During this season a high pressure develops over north India and a north-westerly wind blows down the Indus and Ganges valleys.
In south India, the general direction of wind is from east to west. The mean temperature increases from north to south, the decrease being sharp as one moves northwards in the north-western part of the country. Daily minimum temperatures range from 22°C in the extreme south, to 10°C in the northern plains and 6°C in Punjab.
The rain during this season generally occurs over the Western Himalayas, Tamilnadu and Kerala. Western disturbances and associated trough in westerlies are main rain bearing system in northern part of the country. The jet stream plays a dominant role in bringing these disturbances to India. These disturbances cause rainfall in Punjab, Haryana and Himachal Pradesh, and snowfall in the hills of Jammu and Kashmir. This rainfall is very useful for the cultivation of winter wheat.
The hot weather season(Summer)
The hot weather season also known as pre-monsoon season. During this season, the vertical rays of the sun falls over the peninsular India. There is a steady increase in temperature from south to north.
Summer is hot and dry in the entire country in the initial part of this season. Weather over the land areas of the country is influenced by thunderstorms with rain. Sometimes with hail mostly in the middle and later part.
Temperature starts increasing all over the country during this season. By April, the interior parts of south India record daily temperatures of 30°C–35°C. Central Indian land mass becomes hot with day-time maximum temperature reaching about 40°C at many locations.
Many stations in Gujarat, North Maharashtra, Rajasthan, and North Madhya Pradesh exhibit high daytime and low night-time temperatures during this season. Due to atmospheric pressure conditions, the winds blow from southwest to northeast direction in the Arabian Sea and Bay of Bengal.
They bring pre monsoon showers to the west coast during the month of May. There are few thunder showers called “Mango Showers” which helps in quick ripening of mangoes along the coast of Kerala and Karnataka. “Norwesters” or “Kalbaisakhis” are the local severe storms or violent thunderstorms associated with strong winds and rain lasting for short durations.
It occurs over the eastern and north eastern parts over Bihar, West Bengal and Assam during April and May. They approach the stations from the north-westerly direction.
The Monsoon season also known as the southwest monsoon season. The monsoon is the most significant feature of the Indian climate. The onset of the southwest monsoon takes place normally over the southern tip of the country by the first week of June, advances along the Konkan coast in early June and covers the whole country by 15th July. The monsoon is influenced by global phenomenon like ElNino.
Prior to the onset of the southwest monsoon, the temperature in north India reaches upto 46°C. The sudden approach of monsoon wind over south India with lightning and thunder is termed as the ‘break’ or ‘burst of monsoon’. It lowers the temperature of India to a large extent.
The monsoon wind strikes against the southern tip of the Indian landmass and gets divided into two branches. One branch starts from the Arabian sea and the other from the Bay of Bengal.
The Arabian sea branch of southwest monsoon gives heavy rainfall to the west coast of India as it is located on the windward side of the Western Ghats. The other part which advances towards the north is obstructed by the Himalayan Mountains and results in heavy rainfall in the north.
As Aravalli Mountain is located parallel to the wind direction, Rajasthan and western part do not get much rainfall from this branch. The wind from Bay of Bengal branch moves towards northeast India and Myanmar. This wind is trapped by a chain of mountains namely Garo, Khasi and Jaintia are mainly responsible for the heaviest rainfall caused at Mawsynram located in Meghalaya.
Later on, this wind travel towards west which results in decrease in rainfall from east to west. Over all about 75% of Indian rainfall is received from this monsoon. Tamilnadu which is located in the leeward side receives only a meagre rainfall.
Post monsoon season(Autumn)
It is known as the Northeast monsoon season. The southwest monsoon begins to retreat from north India by the end of September due to the southward shifting pressure belts. The southwest monsoon wind returns from Indian landmass and blows towards Bay of Bengal. The Coriolis force deflects this wind and makes it to blow from northeast.
The season is associated with the establishment of the north-easterly wind system over the Indian subcontinent. Andhra Pradesh, Tamilnadu, Kerala and south interior Karnataka receive good amount of rainfall accounted for 35% of their annual total.
Many parts of Tamilnadu and some parts of Andhra Pradesh and Karnataka receive rainfall during this season due to the storms forming in the Bay of Bengal. Large scale losses to life and property occur due to heavy rainfall, strong winds and storm surge in the coastal regions.
The day time temperatures start falling sharply all over the country. The mean temperature over the northwestern parts of the country shows a decline from about 38°C in October to 28°C in November.
Distribution of rainfall
The average annual rainfall of India is 118 cm. The spatial distribution of rainfall in the country is highly uneven. About 11% area receives over 200 cm of annual rainfall, 21% area receives 125 to 200 cm, 37% area receives 75 to 125 cm, 24% area gets 35 to 75 cm and 7% area gets less than 35 cm.
The Western coast, Assam, South Meghalaya, Tripura, Nagaland, and Arunachal Pradesh are the heavy rainfall areas that get more than 200 cm rainfall. The whole of Rajasthan, Punjab, Haryana, Western and Southwestern parts of Uttar Pradesh, Western Madhya Pradesh, the entire Deccan Trap, or Plateau region east of Western Ghats except for a narrow strip along Tamilnadu coast receives a low rainfall of less than 100 cm. The rest of the areas receive a rainfall ranging between 100 and 200 cm.