Chapter 4 Climate

Mawsynram receives the highest rainfall in the world. It is situated in the East Khasi Hills locality of Meghalaya in north-eastern India, 65 kilometers from Shillong. It is claimed to be the wettest place on Earth, with an average rainfall of 11,872 millimeters every year. Due to the high elevation, it rarely gets truly hot in Mawsynram.

The wind blowing in the northern plains in summers is Loo. It is a resilient, hot and dry summer wind that blows over the western Indo-Gangetic Plain area of North India and Pakistan. The Loo primarily originates in the large desert areas of the northwestern Indian subcontinent, the Great Indian Desert, the Cholistan Desertand the desert areas of Southern Baluchistan.

Western disturbances are the cause of most winter and pre-monsoon seasonal rainfall across the northwest India. Western disturbances are usually linked with gloomy sky, dropping of night temperature and unusual rains.

Monsoon normally arrives in India in early June. It is traditionally defined as a periodic reversing wind complemented by resultant variations in precipitation. The southwest summer monsoon is a four-month period lasting from June to September when enormous convective rainstorms dominate India's weather. India has an average rainfall of 118 centimeters.

Seasons occur due to shift in the Earth’s position. The cold weather season begins during mid-November in Northern India and stays till February. Cold winds originated from the west are the chief agent of winter season. Due to the presence of Sun, the days are warm and nights are cold. This season helps in cultivation of Rabi crops.

India's climate is strongly influenced by the Himalayas and the Thar Desert. Monsoon winds, the geographical location of the country, winds blowing from the West and other relief features of the earth play a great role in directing the climate of India.

The contribution of various geographical factors affecting the climate:

(i) Monsoon winds: India's climate is controlled by monsoon winds. In summer, monsoons are onshore winds. These winds give most of the rainfall to the country. In winter the monsoon winds blow from land to sea as N.E. Monsoons. These are dry winds.

(ii) The extent of the country: India is a vast country. The northern part lies in the temperate region and experiences hot summers and cool winters. The southern part lies nearer the equator and has hot season throughout the year.

(iii) Location of the Himalayas: The Himalayas act as a climatic barrier. This mountain wall protects India from the cold winds of Central Asia in winter. The Himalayas check the on-shore. S.W. Monsoons and force these to give rainfall.

(iv) The Indian Ocean: India lies at the head of the Indian Ocean. S.W. Monsoons originate from this ocean in summer and give rainfall over most of the country. Cyclones also originate over this ocean.

(v) The western disturbances: The western disturbances (cyclones) originate from the Mediterranean Sea and enter India in winter. They are responsible rainfall in north-western parts of India in winter.

(vi) Distance from the sea: The coastal areas experience marine climate. Generally, these areas have an equable climate, but the interior regions experience an extreme or continental type of climate, e.g. north-west India.

(vii) Relief of the land: Relief influences the distribution of temperature and rainfall in India. Mountainous areas have low temperatures. The windward slopes such as the Western Ghats receive heavy rainfall while the leeward slopes (Deccan Plateau) lie in the rain-shadow and are dry.

India has a monsoon type of climate because:

(i) It is strongly directed by the monsoon winds.

(ii) Monsoon in India is further divided into Pre-monsoon, monsoon and post-monsoon seasons.

(iii) India exists in the tropical area (viz. half of it is located at the south to the Tropic of Cancer between 20°N and 20°S).

(iv) The atmospheric conditions, surface winds, upper air circulation, western disturbances and tropical cyclones play a significant role in controlling the climate of the country.

(v) There is an active corolis force that deflects winds towards the right in the Northern Hemisphere and left in the Southern Hemisphere.

The climate of India is strongly influenced by monsoon winds. The mariners who travelled to India in historical times were the first ones to have noticed a phenomenon of the monsoon. They witnessed the benefit from the reversal wind system when they came to India by ships. India has a monsoon type of climate due to its geographical location. On the northern side, India is surrounded by Himalayas and on its eastern side there are many mountain ranges that fetch cool breeze.

The north-western parts of India, like Haryana, Punjab, Rajasthan, UP., Delhi, experience diurnal temperature. Here the temperature goes up to 48 Celsius. This happens because thelow pressure conditions intensify the north-western parts during May-June. Also, the south-west monsoon enters in peninsular India, which increases humidity in its north-western parts.Hot, dry winds namely Loo, starts blowing and dust storms spurt as south-westerly winds blow violently to compensate the low pressure condition formed in north-western parts of the country.

The north-western India is surrounded by the desert. The desert sand becomes hot during the day and quickly cools down in the night which affects the daytime temperature of the neighboring regions.

Malabar coast falls in the Arabian Sea branch of monsoon or western trade winds that do heavy rainfall in Malabar. Collision of rain bearing clouds against elevated landforms of Western Ghats causes rain in Malabar region during the month of July every year.

The Coromandal Coast receives rainfall due to North-eastern winds.

Jet streams are high-velocity westerly winds blowing through a narrow zone, around 12,000 meters over the troposphere. These are actually, westerly winds blowing at higher altitude. Their velocity (speed) recorded in summer is about 110 km/h and about 184 km/h. in winter. These blow at the mid-latitude and over sub-tropical regions (north half of India).

These streams are located over 27-30° north latitude. The westerly flows are responsible for western disturbances and the easterly flows cause tropical depressions during monsoon and even in early winter season.

Monsoons are generally rain bearing and directing winds. This term has been derived from the Arabic word "mausim” first used by the Arab traders who used to visit India for trading purposes through sea routes. It means season. We therefore, can state them seasonal reversal of the wind system in monsoon.

"Monsoon Break refers to the happening of wet and dry spells during the rainy season. Monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals. The monsoon rains take place for a few days continuously with some rainless breaks. These wet and dry spells of the monsoon rains is termed as monsoon break.

The term "unifying bond" implies an attachment or affection of something with another. India has a unique combination of seasons. The different parts of the country experience different climates during the same time. Though different parts of the country have a different climate at the same time, Monsoon is a period which happens to come around the same time every year. The seasonal reversal of the wind system provides a rhythmic cycle of seasons. Indian festivities, plant and animal lives, agricultural calendar, etc. share close ties with the monsoon. Hence, monsoon acts as a unifying bond in India.

The rainfall decreases from east to the west in Northern India because monsoon rises from both the Arabian Sea and the Bay of Bengal, which causes heavy rainfall in the Brahmaputra valley and the Assam hills. As soon as they move toward Himalayas they take western turn and move up the Ganga valley, but due its westward approach it become drier and drier resulting in lesser rainfall North West India. The shrinking moisture levels results in decrease in rainfall from east to the west.

In winters, the sun moves toward the south, the low pressure channel over the northern plains becomes feebler causing the monsoon wind to blow from northeast to south during this period. During summers, low pressure area develops in the interior of Asian continent impacting the North-Western India. Because of this sea begin to blow toward the landmasses. The shift in the progress of monsoon combined with the variation in season causes reversal of wind direction in the Indian sub-continent.

The bulk of rainfall in India is received during the four months of the rainy season i.e. June, July, August and September. This is the period of South-West Monsoons blowing from sea to land. These sea to land Winds are the rain giver, as these moisture-laden winds are on-shore winds. The tropical cyclones add to the amount of rainfall. Easterly tropical jet stream, too, helps in the monsoonal rain during this period.

Tamil Nadu gets rain during monsoons due to the southwest monsoon winds which blow towards the northern hemisphere. In winters, it receives rainfall due to the northeast trade winds. They are offshore winds which blow from land to sea but due to India's topography, they change direction and flow over the Bay of Bengal and pick up moisture. Thus when they blow towards Tamil Nadu coast during winter, they bring rains.

Tropical cyclones are depressions originating over Bay of Bengal. These tropical cyclones are often destructive. They cause heavy rains. These cyclones strike West Bengal and Bangladesh (Ganga Delta). They cross theEastern coast and affect the states of Orissa, Andhra Pradesh, Tamil Nadu and Kerala. The thickly populated deltas of Mahanadi, Godavari, Krishna and Kaveri are the main targets of these tropical cyclones.

The western part of Rajasthan is desert. It gets an annual rainfall less than 20 cms. Rajasthan is under the influence of South West Summer monsoons. The Aravallis system lies parallel to the direction of South West monsoons coming from Arabian Sea. So these low mountain system is unable to check these winds, so western Rajasthan is practically dry. The southern parts get some rainfall. This area lies at a great distance from the Bay of Bengal. The Bay of Bengal monsoons become dry and lose their moisture when they reach Rajasthan. Also, Rajasthan and Gujarat are ata great distance from the Himalayan region so, theydo not come under the influence of monsoons giving rain in the sub-Himalayan region. The leeward slopes of Western Ghats remain in rain-shadow, but there is no guarantee of rainfall hence, this area also comes under the drought prone areas of the country.

In India, there are perceptible regional variations in climatic conditions within the country.

(i) In summer, the temperature may be 50°C or more in some parts of Rajasthan desert, whereas it may be around 20°C in Pahalgam in Jammu and Kashmir. On a winter night, the temperature at Dassin Jammu and Kashmir may be as low as -45°C, while Thiruvananthapuram may have a temperature of +20°C.

(ii) In certain places there is a wide difference between day and night temperatures. In the Thar Desert, the day temperature may be 50°C and drops down to near freezing point the same night. On the other hand, there is hardly any difference between day and night temperatures in the Andaman and Nicobar Islands or in Kerala.

(iii) While precipitation is mostly in the form of snowfall in the upper parts of Himalayas, it only rains over the rest of the country.

(iv) The annual precipitation varies from 400 cm in Meghalaya to less than 10 cm in Ladakh and Western Rajasthan.

(v) Most parts of the country receive rainfall from June to September, but Tamil Nadu coast receives rainfall during autumn and early winter.

To understand the mechanism of monsoons the following facts are important

(i) The difference in the rate of heating and cooling of land and sea on a large scale. During summers a low pressure area develops on the Indian landmass while the seas around experience comparatively high pressure.

(ii) The shift of the position of the Inter-Tropical Convergence Zone. This is the equatorial trough normally positioned about 5°N of the equator, also known as the monsoon trough during the monsoon season.

(iii) The presence of high pressure area, east of Madagascar approximately at 20°S over the Indian Ocean. The intensity and position of this high pressure area affects the Indian monsoons.

(iv) The Tibetan high level plateau gets intensely heated during summers which results in strong vertical currents and formation of high pressure over the plateau at about 9 kilometers above sea level.

(v) The movement of the westerly jet to the north of the Himalayas and the presence of the tropical easterly jet over the Indian peninsula during summers.

Apart from this, it has also been noticed that changes in the pressure conditions over the southern Oceans also affect the monsoons.

The temperature, atmospheric pressure, wind, humidity and precipitation usually determine the weather conditions at any point of time (a day or a week) and space. Weather is generally expressed as cool, hot, windy, calm, cloudy, bright, wet or dry. Actually, atmospheric conditions are called the weather. We experience hot weather in summers, cold weather in winters, wet weather in the rainy season and cool and dry during October-November and the March and April respectively.

Weather phenomenon changes rapidly. Any day may have different weather conditions. We just feel suffocated due to humidity and scorching heat of July month. Suddenly the clear sky is covered with clouds and it starts raining with lightning and strong wind. Something of such strange happens when cyclonic depression causes damages in deltas of the Mahanadi, Kaveri, Godavari and Krishna rivers.

Following are the characteristics of the cold season:

(i) It begins from mid-November in Northern India and pervades here till February. The mid-months, i.e., December and January are the coldest months.

(ii) The temperature gradually decreases during this period from the south to the north. For example, in Chennai 20°-25°C while it is 10°15°C in northern plains.

(iii) Days are experienced warm while the nights are cold. Days are cut short while nights are longer.

(iv) Most part of the country remains dry (i.e., without winter rain) during this period and only Tamil Nadu coast including Coromandel coast receive heavy winter rains.

(v) Coastal areas enjoy moderate temperature throughout the year while the rest of the country experiences cold, heat, humid and moderate according to the cycle of the seasonal change. It means the reversal of winds or monsoon type climate has more seasonal variations to experience.

The characteristics of Monsoon season is discussed below:

a. It gives water in to most of theparts of the country except some leeward sides’ rain shadow regions and desert areas.

b. Early in the season, the windward side of the Western Ghats receives heavy rainfall of more than 250 cm.

c. The rain shadow areas of Deccan Plateau and parts of Madhya Pradesh also get scanty rains.

d. The maximum rainfall is recorded in the north-eastern parts of the country. Mawsynram happens to be the wettest place in the world.

e. Indian monsoon takes “breaks” viz. sprinkled with rainless intervals. This happens because of the monsoon trough, caused due to spatial distribution of rainfall.

f. The frequency and intensity of tropical depressions also determine the amount and duration of monsoons.

g. The monsoon trough over the northern plains becomes weaker causing the months of October-November, a period of transition from hot rainy season to dry winter conditions.

The effects of Monsoon season is discussed below:

a. When the rains are heavy, the rivers get flooded causing heavy damage in the plains year after year.

b. A dry spell would cause as much misery as the river floods.

c. The characteristic of monsoon has a very destabilizing effect on Indian economy that continues to be predominantly agricultural and severely dependent on rained irrigation.

(i) The Western Coast and NorthEastern India receives rainfall over 400 cm. Mawsynram and Cherrapunji in Meghalaya are known for receiving maximum rainfall in the world. The Andaman Islands and Lakshadweep Islands are also known to receive annual rainfall above 400 cm.

(ii) The parts of Northern Kashmir, Western Rajasthan, Deccan plateau and Punjab are known to be the areas that receive scanty rainfall that is less than 20 cm. In Northern part of India, rainfall decreases toward the west, while in the peninsular region except for Tamil Nadu, the rainfall decreases eastwards.

(iii) South west monsoon is a compound and a self-evolved weather system unique to Indian subcontinent. The south west monsoon in India moves in south-west direction. In India there are only south-west and north-east monsoons. Because of the corolis effect, the south-east monsoon becomes south west trade winds.

A. Dances:

a. Bharatnatyam: This is a multi-dimensional dance form that has been able to retain the principles enunciated in Bharata's Natya Bhasha. It has survived in the precincts of South Indian temples. It is a solo dance by women. This dance form has three aspects at functional level; namely Nritta, Nritya and Natya. Kerala, Tamil Nadu states are the regions where this dance is performed.

b. Manipuri: As the name itself implies, this dance is originated from Manipur state of India. The Manipuri dance form is called Jagoi is considered to be one of the major dance forms of the country. Only movement of body and not codified gestures and expressions are incorporated with this dance. The dancer puts on a gorgeous dress covering her face with a veil and a skirt embedded with mirrors.

c. Kathkalli: This dance is performed in Kerala state. A story is expressed through the gestures and expressions with this dance. It embodies in a high degree the principles laid down in the ancient Hindu scriptures of dance and drama.

d. Kathak: It is performed in north India (Delhi, Haryana, U.P., Rajasthan etc.). It was patronized by the rulers of the north Indian princely states during the British regime.

B. Languages:

a. Hindi: Throughout India barring some southern states.

b. Urdu: It is spoken in Muslim majority states.

c. Bengali: It is spoken mostly in West Bengal and some parts of Orissa and Bihar. (iv) Gujarati: In Gujarat state,

d. Marathi: In Maharashtra state.

e. Dravidian Languages: It is a group of Tamil, Telugu, Kannada and Malayalam spoken inthe states of Tamil Nadu, Andhra Pradesh, Karnataka and Kerala.

C. Festivals:

a. Diwali: Diwali, the most prominent Hindu festival of India, is celebrated with a lot of pomp and show. Diwali is a festival of lights and decoration.

b. Holi: Holi signifies the victory of good over evil and the arrival of spring.Holi is the festival of colors. This festival is celebrated all over the country.

c. Durga Puja: One of the important festivals of India, Durga Puja is celebrated with grandeur by Bengalis, throughout the country. It commemorates Lord Rama’s invocation of Goddess Durga before going to war with the demon king Ravana.

d. Guru parb: The most important Sikh festival of India, special assemblies on the lives and teachings of the gurus, and langars (community meals) are organized in the gurudwaras. Karah Prasad is distributed among all, and hymn chanting processions are held in the city.

e. Eid: Eid is one of the major festivals of India for the Muslim community. People dress up in fineries, attend a special community prayer in the morning, visit friends, and relatives and exchange sweets. Children are given idi(money or gift) by elders.

f. Bihu: Popular among the festivals of India celebrated in the North East, Bihu is the harvest festival of Assam.

g. Pongal: The four-day long harvest festival of South India is one of the most famous festivals of India. People prepare Pongal dish and wear their traditional attire. Celebrities include bonfires, dance, cattle races, sweets, and savories.

Note:- We can sum-up these dances in context to the states they performed as under:

Note: Students are advised to ask their parents, teachers or read concerned literature on Indian folk lore and seasonal cuisines. Generally, every child knows what types of diets/foods are prepared by his mother commiserating with the changing seasons. Similarly, there are songs like Chaiti, Malhar, Sravani, Barakha-Geet and Viraha etc. Thus, they may enhance their knowledge about the songs, cuisines, festivals and seasonal arts associated with the changing seasons particularly in their respective villages, districts and states.

a. Desert areas-

The climate in the deserts is extreme. The summers are very hot and dry. Sandstorms are common in this season. Water becomes scarce and in many places there is severe drought. Most places receive little or no rainfall.

b. North eastern areas-

Northeast is not a single unit. It consists of of 7 states with people belonging to diverse cultures, ethnic groups and religions. A person living in Assam will have a very different lifestyle from an individual living at Manipur. Life in the cities and small towns is different from life at far flung villages. However, there’s one characteristic in most Northeastern states that is common and that is simplicity.

c. South India

Different states of South India have different cultures. Different states have their own festivals, dance forms and food preferences. The climate however, is similar in these states due to their close geographical proximity.

Hint: Students should try and find out the climatic features of different parts on the basis of examples provided above and find out the different types of houses found in the different areas.

(i)

(ii)

(i) Shillong and Mumbai are the rainiest stations of India. Shillong is a hill station in northeast India and capital of the state of Meghalaya. It’s known for the manicured gardens at Lady Hydari Park. Mumbai is a densely populated city on India’s west coast. A financial center, it's India's largest city. The city's also famous as the heart of the Bollywood film industry.

(ii) Leh and Jodhpur are the driest stations of India. Leh, a high-desert city in the Himalayas, is the capital of the Leh region in northern India’s Jammu and Kashmir state. Jodhpur is a city in the Thar Desert of the northwest Indian state of Rajasthan.

(iii) Thiruvananthapuram and Chennai have equable climate. Thiruvananthapuram is the capital of the southern Indian state of Kerala. Chennai is located on the Bay of Bengal in eastern India, is the capital of the state of Tamil Nadu.

(iv) Jodhpur and Delhi have most extreme stations.

(v) Mumbai and Thiruvanthapuram. The total area of Mumbai is 603 sq. km and the usual weather is 29°C, with an average humidity of about 79%. The total areas of Thiruvanthapuram is 214 sq. km. Thiruvanthapuram doesn’t have much variation in the climate. In summer the maximum temperature goes up to 35°C and minimum reaches to 22°C. The place is extremely humid in summers.

(vi) Kolkata and Shillong. In the month of June Kolkata receives rain from the Bay of Bengal and in the month of July, the rainfall is influenced by the Arabian Sea branch. However, Shillong receives rainfall from only Bay of Bengal branch only.

(vii) Delhi and Kolkata. Due to their geographic location, both Delhi and Kolkata are influenced by both the branches of south-west monsoons. When the monsoon is influenced by the Bay of Bengal branch, these stations receive more rainfall as compared to the Arabian Sea branch.

(viii) Chennai and Bengaluru. During the retreat and north-east monsoon, cities of Southern India receive rainfall as they do not get much rainfall during the normal south-west monsoon. The north eastern monsoon takes place from December to March when the surface high-pressure system is strong.

(ix) Delhi and Jodhpurare the cities that receive winter showers due to western disturbances. Western Disturbances are important for the development of the Rabi crop, which includes the locally important staple wheat. Western disturbances originate in the Mediterranean region. An average of four to five western disturbances takes place during the winter season. The rainfall distribution and amount varies with every western disturbance.

(x)(a) February: Thiruvananthapuram and Mumbai.

(b) April: Nagpur and Chennai.

(c) May: Nagpur and Jodhpur.

(d) June: Nagpur and Delhi.

(i) Thiruvananthapuram receives the rainfall caused by South West monsoon winds instantly as it is located on proximity to Indian Ocean. Monsoon winds enter here on 1st June every year and it receives heavy rains. Shillong receives rainfall by virtue of the Bay of Bengal branch of the S.W. monsoon. As monsoon winds change their course in July, it receives less rain in that month.

(ii) Mumbai falls in proximity to the Arabian Sea and monsoon winds starts blowing here in the second week of June. The monsoon takes time to reach to the places that are away from the coastal areas. In the subsequent weeks of June, the monsoon reaches to Thiruvananthapuram and Andhra Pradesh and from here it travels further.

(iii) Chennai falls in the rain shadow area of Eastern Ghats (i.e., at Coromandal Coast). Due to this, it receives scanty rain as compared to the South West monsoon winds of the Konkan Coast on the Western Ghats.

(iv) Shillong receives rain from both branches of South West monsoon viz. Bay of Bengal and that of Arabian Sea branch. The Bay of Bengal branch collides against the high peaks of mountains here and does heavy rain. Kolkata, on the other hand, is deprived of rain by the Bay of Bengal branch of south-west monsoon hence; this station receives rain only from the Arabian Sea branch of South West monsoon.

(v) Kolkata is rainier in July than in June unlike Shillong because it belongs to the Bay of Bengal branch of south-west monsoon. In July, Kolkata receives rain from the Arabian branch of southwest monsoon. While Shillong gets rain from Bay of Bengal branch in July and hence; it is rainier than Kolkata.

(vi) Both branches of South West monsoon (viz. Bay of Bengal branch and Arabian Sea branch) collide against the high mountain peaks inAssam, Meghalaya and Tripura and pour there heavily. Their route is than diverted to the west and these pour water in the northern plains. Delhi also falls adjacent to northern plains. The Arabian Sea branch of monsoon also enters here. It comes with motion parallel to Aravalis, pours its water on Delhi and then moves towards Jammu and Kashmir through Chandigarh on its way. Jodhpur falls in Rajasthan where Aravalli give easy way to forward this branch of monsoon resulting in scanty or no rain in Jodhpur. It falls in rain shadow area wherefrom clouds go but do not rain.

(i) Equable climate generally is experienced in all stations falling nearer to the sea as the moisture does not allow high pressure to be formed any time here. This fact, also applies on Thiruvananthapuram and we see here equable climate throughout the year.

(ii) South-West Monsoon Winds start retreating in September to October months. These are replaced by the North-East trade winds, i.e., winds blowing from extreme northwest of India. These winds receive vapor while moving over the Bay of Bengal to which they immediately carry to the Coromandal Coast in Tamil Nadu. These rain-bearing winds collide against Eastern Ghats and thus, Coromandal including Chennai receives heavy rain during winter season (viz. in November-December).

(iii) Jodhpur falls in the rain shadow region and it is situated proxy to the Thar desert. This station has therefore, extreme climate and dusty as also hot winds namely "Loo" starts blowing here during summer. As the water-bearing winds pass over it without raining, this station remains arid throughout the year.

(iv) North-east trade Winds blow throughout the year in Leh district of Jammu and Kashmir state. Monsoon winds never reach up to this altitude as they get lost their water completely. This station receives mostly snowfall because of its super altitude. Being it the coldest place, water-drops are frozen here. Thus, no rainfall or scanty precipitation we can only see here.

(v) Monsoon winds always prefer to blow over Thiruvananthapuram and Shillong irrespective of their distance from the sea. The winds blowing from Indian Ocean, Bay of Bengal and that of Arabian Sea simultaneously cover these stations during rainy season. Disturbances are caused over Andaman Sea and the Bay of Bengal as a result of the North-East trade winds

Usually fill the void created by the retreating monsoon during winter season. These winds while passing over above said sea; generally get vapor and do heavy rain in Shillong and Thiruvananthapuram. Thiruvananthapuram falls adjacent to the Arabian sea and Indian Ocean and Shillong is also nearer to Bay of Bengal and Andaman Sea. Delhi and Jodhpur are at larger distance from the sea coupled with nearer to the terrestrial region as also falling sub-tropical belt. Hence, both these stations receive heavy rain during three months while these remain dry during the next nine months of the year. We can state in brief that quantum of rain here is affected due to different landforms, temperature, distance from the sea and mean altitude from the sea level.