Climate

Hello students, welcome to today's geography lesson. I'm so happy to see you all here, ready to learn about one of the most fascinating aspects of our beautiful country – the climate of India. Before we begin, let me tell you that climate affects everything in our lives – from the food we eat to the clothes we wear, from the houses we live in to the festivals we celebrate. So, this chapter is not just about facts and figures – it's about understanding the very rhythm of life in our country.

Let's start by understanding what climate actually means. Now, students, you might have heard people say "the weather is pleasant today" or "it's very hot outside" – these are things we experience every day. But what is the difference between weather and climate? This is a very important distinction that many students get confused about, so pay close attention.

Weather refers to the state of the atmosphere over an area at any particular point of time. For example, if I ask you "what's the weather like today?" you might say "it's sunny" or "it's raining" or "it's cloudy." That's weather – it's what's happening right now, at this moment. Weather can change within hours or even minutes. One moment it might be sunny, and suddenly dark clouds appear and it starts raining. That's weather for you – very unpredictable and changeable.

Climate, on the other hand, refers to the sum total of weather conditions and variations over a large area for a long period of time – specifically, more than thirty years. So when we talk about the climate of India, we're talking about the overall pattern of weather that India experiences over many, many years. We don't say "India's weather is hot" – we say "India has a hot climate" because we're talking about the long-term pattern. Do you understand the difference? Let me give you another example. If it rains heavily for one day in Delhi, that doesn't mean Delhi has a rainy climate. But if Delhi receives rainfall almost every year during the monsoon months, then we say Delhi has a monsoon climate. That's the difference between weather and climate.

Now, students, what are the elements or components of weather and climate? They are essentially the same – temperature, atmospheric pressure, wind, humidity, and precipitation. These five elements keep changing from day to day, and when we study them over many years, we get the climate pattern of a place.

You may have noticed that weather conditions fluctuate very often even within a day. But there is some common pattern over a few weeks or months – for instance, days are cool or hot, windy or calm, cloudy or bright, wet or dry. On the basis of the generalised monthly atmospheric conditions, the year is divided into seasons such as winter, summer, or rainy seasons. In India, we typically experience four main seasons, and we'll learn about each one in detail.

Now, let me ask you a question. Do you know what type of climate India has? The climate of India is described as the 'monsoon' type. This is very important, students – whenever someone asks you about India's climate, your answer should be "monsoon type climate." In Asia, this type of climate is found mainly in the south and the southeast. The word "monsoon" is derived from the Arabic word "mausim" which literally means season. So when we say monsoon, we're essentially talking about seasonal winds. Monsoon refers to the seasonal reversal in the wind direction during a year. This is a key characteristic of India's climate – the winds change direction completely with the seasons, and this brings us rain, heat, and cold at different times of the year.

Despite an overall unity in the general pattern, there are perceptible regional variations in climatic conditions within the country. This means that while all of India experiences monsoon climate, different parts of the country have slightly different weather patterns. Let me give you some examples to understand this better.

Let's talk about temperature first. In summer, the mercury occasionally touches 50°C in some parts of the Rajasthan desert, whereas it may be around 20°C in Pahalgam in Jammu and Kashmir. That's a huge difference of 30 degrees! On a winter night, temperature at Drass in Jammu and Kashmir may be as low as minus 45°C – that's extremely cold! Thiruvananthapuram, on the other hand, may have a temperature of 22°C even in winter. So you can see that India has extreme variations in temperature from one region to another.

There's another interesting thing about temperature. In certain places there is a wide difference between day and night temperatures. In the Thar Desert, the day temperature may rise to 50°C and drop down to near 15°C the same night. That's a difference of 35 degrees between day and night! On the other hand, there is hardly any difference in day and night temperatures in the Andaman and Nicobar islands or in Kerala. This is because coastal areas are moderated by the sea – the sea keeps the temperature stable. We'll learn more about this when we discuss factors affecting climate.

Now let's look at precipitation – that means rainfall and snowfall. There are variations not only in the form and types of precipitation but also in its amount and the seasonal distribution. While precipitation is mostly in the form of snowfall in the upper parts of Himalayas, it rains over the rest of the country. The annual precipitation varies from over 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan. That's a huge difference – some places get 400 times more rainfall than others! Most parts of the country receive rainfall from June to September. But some parts like the Tamil Nadu coast gets a large portion of its rain during October and November. This is because of the retreating monsoon, which we'll study later.

In general, coastal areas experience less contrasts in temperature conditions. Seasonal contrasts are more in the interior of the country. 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. This is why we see so much diversity in India – the climate is so varied from region to region!

Now, students, I want you to think about something. Why do the houses in Rajasthan have thick walls and flat roofs? Let me explain. Rajasthan is a desert area with extreme temperatures – very hot in summer and very cold in winter. Thick walls provide insulation, keeping the inside cool during hot days and warm during cold nights. Flat roofs are suitable because Rajasthan receives very little rainfall, so there's no need for sloped roofs to drain water. Now, why do houses in the Tarai region and in Goa and Mangalore have sloping roofs? These areas receive heavy rainfall, so sloping roofs help the water to flow off quickly. And why are houses in Assam built on stilts? Assam experiences floods during the monsoon season, so houses built on stilts remain safe from floodwaters. You see, students, our climate directly influences our architecture and way of living!

Now let's move on to the factors that affect India's climate. There are six major controls of the climate of any place. They are: latitude, altitude, pressure and wind system, distance from the sea (continentality), ocean currents, and relief features. Let me explain each one in detail.

First, let's talk about latitude. The Tropic of Cancer passes through the middle of the country from the Rann of Kuchchh in the west to Mizoram in the east. Almost half of the country, lying south of the Tropic of Cancer, belongs to the tropical area. All the remaining area, north of the Tropic, lies in the sub-tropics. Therefore, India's climate has characteristics of tropical as well as subtropical climates. This is why southern India is generally warmer than northern India.

Second, let's discuss altitude. India has mountains to the north, which have an average height of about 6,000 metres – I'm talking about the Himalayas. India also has a vast coastal area where the maximum elevation is about 30 metres. The Himalayas prevent the cold winds from Central Asia from entering the subcontinent. It is because of these mountains that this subcontinent experiences comparatively milder winters as compared to central Asia. Can you imagine what would happen if those cold winds entered India? It would be extremely cold in winter! So we should be grateful to the Himalayas for protecting us.

Third, we have pressure and winds. The climate and associated weather conditions in India are governed by pressure and surface winds, upper air circulation, and western cyclonic disturbances and tropical cyclones. The pressure and wind conditions over India are unique. During winter, there is a high-pressure area north of the Himalayas. Cold dry winds blow from this region to the low-pressure areas over the oceans to the south. In summer, a low-pressure area develops over interior Asia, as well as over northwestern India. This causes a complete reversal of the direction of winds during summer. This reversal is what gives us the monsoon!

Let me explain the concept of latitude and altitude a bit more, as these are important for understanding climate. Due to the curvature of the earth, the amount of solar energy received varies according to latitude. As a result, air temperature generally decreases from the equator towards the poles. So places near the equator are hotter than places near the poles. As one goes from the surface of the earth to higher altitudes, the atmosphere becomes less dense and temperature decreases. The hills are therefore cooler during summers. This is why hill stations like Shimla and Mussoorie are so pleasant in summer – they're at high altitude!

The pressure and wind system of any area depend on the latitude and altitude of the place. Thus it influences the temperature and rainfall pattern. The sea exerts a moderating influence on climate: As the distance from the sea increases, its moderating influence decreases and the people experience extreme weather conditions. This condition is known as continentality – that is, very hot during summers and very cold during winters. This is why places far from the sea, like Rajasthan, have extreme temperatures. Ocean currents along with onshore winds affect the climate of the coastal areas. For example, any coastal area with warm or cold currents flowing past it will be warmed or cooled if the winds are onshore.

Now, students, let me tell you about the winds that affect India. India lies in the region of north easterly winds. These winds originate from the subtropical high-pressure belt of the northern hemisphere. They blow southwards, get deflected to the right due to the Coriolis force, and move towards the equatorial low-pressure area. Generally, these winds carry little moisture as they originate and blow over land. Therefore, they bring little or no rain. Hence, India should have been an arid land, but it is not so. Let me tell you why!

The Coriolis force is 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. Because of this force, the northeast trade winds blow from land to sea in winter, bringing no moisture. But in summer, the winds reverse direction and blow from sea to land, bringing moisture and rain. This is the magic of the monsoon!

Now let's discuss the seasons in India. The monsoon type of climate is characterised by a distinct seasonal pattern. The weather conditions greatly change from one season to the other. These changes are particularly noticeable in the interior parts of the country. The coastal areas do not experience much variation in temperature though there is variation in rainfall pattern. How many seasons are experienced in your place? Four main seasons can be identified in India – the cold weather season, the hot weather season, the advancing monsoon, and the retreating monsoon with some regional variations.

Let's start with the cold weather season, which is winter. The cold weather season begins from mid-November in northern India and stays till February. December and January are the coldest months in the northern part of India. The temperature decreases from south to the north. The average temperature of Chennai, on the eastern coast, is between 24°C and 25°C, while in the northern plains, it ranges between 10°C and 15°C. Days are warm and nights are cold. Frost is common in the north and the higher slopes of the Himalayas experience snowfall.

During this season, the northeast trade winds prevail over the country. They blow from land to sea and hence, for most part of the country, it is a dry season. Some amount of rainfall occurs on the Tamil Nadu coast from these winds as, here they blow from sea to land. In the northern part of the country, a feeble high-pressure region develops, with light winds moving outwards from this area. Influenced by the relief, these winds blow through the Ganga valley from the west and the northwest. The weather is normally marked by clear sky, low temperatures and low humidity and feeble, variable winds.

A characteristic feature of the cold weather season over the northern plains is the inflow of cyclonic disturbances from the west and the northwest. These low-pressure systems originate over the Mediterranean Sea and western Asia and move into India, along with the westerly flow. They cause the much-needed winter rains over the plains and snowfall in the mountains. Although the total amount of winter rainfall locally known as 'mahawat' is small, they are of immense importance for the cultivation of 'rabi' crops. This winter rainfall is crucial for wheat and other rabi crops. The peninsular region does not have a well-defined cold season. There is hardly any noticeable seasonal change in temperature pattern during winters due to the moderating influence of the sea.

Now, students, here's an interesting question for you. Why are most of the world's deserts located in the western margins of continents in the subtropics? Let me explain. In the subtropics, the trade winds blow from east to west, carrying moisture from the oceans. But on the western margins, these winds blow from land to sea, so they don't bring any moisture. Additionally, cold ocean currents flow along the western margins, which further reduce the possibility of rainfall. That's why deserts are found in these regions – for example, the Sahara Desert is on the western side of Africa, and the Thar Desert is on the western side of India.

Now let's move on to the hot weather season, which is summer. Due to the apparent northward movement of the sun, the global heat belt shifts northwards. As such, from March to May, it is hot weather season in India. The influence of the shifting of the heat belt can be seen clearly from temperature recordings taken during March-May at different latitudes. In March, the highest temperature is about 38°C, recorded on the Deccan plateau. In April, temperatures in Gujarat and Madhya Pradesh are around 42°C. In May, temperature of 45°C is common in the northwestern parts of the country. In peninsular India, temperatures remain lower due to the moderating influence of the oceans.

The summer months experience rising temperature and falling air pressure in the northern part of the country. Towards the end of May, an elongated low-pressure area develops in the region extending from the Thar Desert in the northwest to Patna and Chotanagpur plateau in the east and southeast. Circulation of air begins to set in around this trough.

A striking feature of the hot weather season is the 'loo'. These are strong, gusty, hot, dry winds blowing during the day over the north and northwestern India. Sometimes they even continue until late in the evening. Direct exposure to these winds may even prove to be fatal. Dust storms are very common during the month of May in northern India. These storms bring temporary relief as they lower the temperature and may bring light rain and cool breeze. This is also the season for localised thunderstorms, associated with violent winds, torrential downpours, often accompanied by hail. In West Bengal, these storms are known as the 'Kaal Baisakhi'.

Towards the close of the summer season, pre-monsoon showers are common especially in Kerala and Karnataka. They help in the early ripening of mangoes, and are often referred to as 'mango showers'. These are very welcome because they signal the end of the hot summer and the arrival of the monsoon.

Now let's discuss the advancing monsoon, which is the rainy season. By early June, the low-pressure condition over the northern plains intensifies. It attracts the trade winds of the southern hemisphere. These south-east trade winds originate over the warm subtropical areas of the southern oceans. They cross the equator and blow in a south-westerly direction entering the Indian peninsula as the south-west monsoon. As these winds blow over warm oceans, they bring abundant moisture to the subcontinent. These winds are strong and blow at an average velocity of 30 km per hour. With the exception of the extreme north-west, the monsoon winds cover the country in about a month.

The inflow of the south-west monsoon into India brings about a total change in the weather. Early in the season, the windward side of the Western Ghats receives very heavy rainfall, more than 250 cm. The Deccan Plateau and parts of Madhya Pradesh also receive some amount of rain in spite of lying in the rain shadow area. The maximum rainfall of this season is received in the north-eastern part of the country. Mawsynram in the southern ranges of the Khasi Hills receives the highest average rainfall in the world. Rainfall in the Ganga valley decreases from the east to the west. Rajasthan and parts of Gujarat get scanty rainfall.

Another phenomenon associated with the monsoon is its tendency to have 'breaks' in rainfall. Thus, it has wet and dry spells. In other words, the monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals. These breaks in monsoon are related to the movement of the monsoon trough. For various reasons, the trough and its axis keep on moving northward or southward, which determines the spatial distribution of rainfall. When the axis of the monsoon trough lies over the plains, rainfall is good in these parts. On the other hand, whenever the axis shifts closer to the Himalayas, there are longer dry spells in the plains, and widespread rain occur in the mountainous catchment areas of the Himalayan rivers. These heavy rains bring in their wake devastating floods causing damage to life and property in the plains. The frequency and intensity of tropical depressions too determine the amount and duration of monsoon rains. These depressions form at the head of the Bay of Bengal and cross over to the mainland. The depressions follow the axis of the "monsoon trough of low pressure".

The monsoon is known for its uncertainties. The alternation of dry and wet spells vary in intensity, frequency and duration. While it causes heavy floods in one part, it may be responsible for droughts in the other. It is often irregular in its arrival and its retreat. Hence, it sometimes disturbs the farming schedule of millions of farmers all over the country.

Now let's talk about the retreating monsoon, which is the transition season. During October-November, with the apparent movement of the sun towards the south, the monsoon trough or the low-pressure trough over the northern plains becomes weaker. This is gradually replaced by a high-pressure system. The south-west monsoon winds weaken and start withdrawing gradually. By the beginning of October, the monsoon withdraws from the Northern Plains.

The months of October-November form a period of transition from hot rainy season to dry winter conditions. The retreat of the monsoon is marked by clear skies and rise in temperature. While day temperatures are high, nights are cool and pleasant. The land is still moist. Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive during the day. This is commonly known as 'October heat'. In the second half of October, the mercury begins to fall rapidly in northern India.

The low-pressure conditions over north-western India get transferred to the Bay of Bengal by early November. This shift is associated with the occurrence of cyclonic depressions, which originate over the Andaman Sea. These cyclones generally cross the eastern coasts of India cause heavy and widespread rain. These tropical cyclones are often very destructive. The thickly populated deltas of the Godavari, the Krishna and the Kaveri are frequently struck by cyclones, which cause great damage to life and property. Sometimes, these cyclones arrive at the coasts of Odisha, West Bengal and Bangladesh. The bulk of the rainfall of the Coromandel Coast is derived from depressions and cyclones.

Now let's discuss the distribution of rainfall in India. Parts of western coast and northeastern India receive over about 400 cm of rainfall annually. However, it is less than 60 cm in western Rajasthan and adjoining parts of Gujarat, Haryana and Punjab. Rainfall is equally low in the interior of the Deccan plateau, and east of the Sahyadris. Why do these regions receive low rainfall? A third area of low precipitation is around Leh in Jammu and Kashmir. The rest of the country receives moderate rainfall. Snowfall is restricted to the Himalayan region.

Owing to the nature of monsoons, the annual rainfall is highly variable from year to year. Variability is high in the regions of low rainfall, such as parts of Rajasthan, Gujarat and the leeward side of the Western Ghats. As such, while areas of high rainfall are liable to be affected by floods, areas of low rainfall are drought-prone.

Now, students, I want to tell you something very interesting about the monsoon. You have already known the way the Himalayas protect the subcontinent from extremely cold winds from central Asia. This enables northern India to have uniformly higher temperatures compared to other areas on the same latitudes. Similarly, the Peninsular plateau, under the influence of the sea from three sides, has moderate temperatures. Despite such moderating influences, there are great variations in temperature conditions. Nevertheless, the unifying influence of the monsoon on the Indian subcontinent is quite perceptible. The seasonal alteration of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons. Even the uncertainties of rain and uneven distribution are very much typical of the monsoons. The Indian landscape, its animal and plant life, its entire agricultural calendar and the life of the people, including their festivities, revolve around this phenomenon. Year after year, people of India from north to south and from east to west, eagerly await the arrival of the monsoon. These monsoon winds bind the whole country by providing water to set the agricultural activities in motion. The river valleys which carry this water also unite as a single river valley unit. This is why we say that the monsoon is a unifying bond for India!

Now, students, let's move on to the exercises at the end of the chapter. I want you to pay close attention as I solve each question for you.

Let's start with Exercise 1, Question 1. Which one of the following places receives the highest rainfall in the world? The options are Silchar, Mawsynram, Cherrapunji, and Guwahati. The answer is Mawsynram. Mawsynram in Meghalaya is known as the wettest place on Earth. It receives over 400 cm of rainfall annually. Let me tell you that Mawsynram is also reputed for its stalagmite and stalactite caves. So the correct answer is (b) Mawsynram.

Question 2. The wind blowing in the northern plains in summers is known as: options are Kaal Baisakhi, Loo, Trade Winds, and None of the above. The answer is Loo. The loo is a hot, dry wind that blows during the day over north and northwestern India in summer. Kaal Baisakhi is a type of thunderstorm in West Bengal. Trade winds are the permanent winds that blow from high pressure to low pressure areas. So the correct answer is (b) Loo.

Question 3. Monsoon arrives in India approximately in: options are Early May, Early July, Early June, and Early August. The answer is Early June. The monsoon usually arrives in India by early June, starting from the southwestern coast and then spreading across the country. So the correct answer is (c) Early June.

Question 4. Which one of the following characterises the cold weather season in India? The options are Warm days and warm nights, Warm days and cold nights, Cool days and cold nights, and Cold days and warm nights. The answer is Warm days and cold nights. During winter in northern India, days are relatively warm but nights are quite cold. This is because during the day, the sun heats the ground, but at night, the heat radiates away quickly, making the nights cold. So the correct answer is (b) Warm days and cold nights.

Now let's move on to Exercise 2, Question 1. What are the controls affecting the climate of India? There are six major controls: latitude, altitude, pressure and wind system, distance from the sea (continentality), ocean currents, and relief features. Let me explain each briefly. Latitude determines the amount of solar energy received. Altitude affects temperature – as altitude increases, temperature decreases. Pressure and wind system determines the movement of air masses. Distance from the sea affects how moderate or extreme the climate is. Ocean currents influence coastal climates. Relief features like mountains affect rainfall patterns.

Question 2. Why does India have a monsoon type of climate? India has a monsoon type of climate because of the unique pressure and wind conditions over the Indian subcontinent. During summer, the land heats up faster than the sea, creating a low-pressure area over the interior of Asia. This attracts the moisture-laden south-west monsoon winds from the Indian Ocean. In winter, the situation reverses – the land is cooler than the sea, creating high pressure over land, and the dry north-east monsoon winds blow from land to sea. This complete reversal of wind direction twice a year is the hallmark of a monsoon climate. Additionally, India's position between the Tropic of Cancer and the equator, the presence of the Himalayas in the north, and the varied topography all contribute to making India's climate a monsoon type.

Question 3. Which part of India does experience the highest diurnal range of temperature and why? The part of India that experiences the highest diurnal range of temperature is the Thar Desert in Rajasthan. This is because of the continentality effect – the desert is far from the sea, so there's no moderating influence of the ocean. During the day, the desert floor heats up rapidly under the intense sun, pushing temperatures above 50°C. At night, the heat radiates away quickly into the clear sky, and temperatures can drop to around 15°C the same night. This creates a huge difference of about 35°C between day and night temperatures.

Question 4. Which winds account for rainfall along the Malabar coast? The south-west monsoon winds account for rainfall along the Malabar coast. These winds blow from the Arabian Sea and strike the Western Ghats, causing heavy orographic rainfall on the windward side. The Malabar coast receives heavy rainfall during the monsoon season, often more than 250 cm annually.

Question 5. Define monsoons. What do you understand by "break" in monsoon? Monsoons refer to the seasonal reversal in the wind direction during a year. The word is derived from the Arabic word "mausim" meaning season. A "break" in monsoon refers to the phenomenon where the monsoon rains stop for a few days. During the monsoon season, there are periods of heavy rainfall followed by dry spells or breaks. These breaks occur because the monsoon trough shifts north or south, affecting the distribution of rainfall. When the trough is over the plains, rainfall is good. When it shifts towards the Himalayas, there are dry spells in the plains, but heavy rainfall occurs in the Himalayan catchment areas.

Question 6. Why is the monsoon considered a unifying bond? The monsoon is considered a unifying bond because it binds the entire country together despite its vast size and diversity. The seasonal arrival of the monsoon brings water to agricultural fields across the country, enabling farmers to grow crops. The rhythm of seasons – the cold weather, hot weather, monsoon, and retreating monsoon – provides a cyclical pattern that governs the agricultural calendar, festivals, and daily life of people throughout the country. Whether you are in Punjab or Tamil Nadu, Kerala or Rajasthan, the monsoon brings the promise of water and prosperity. The river valleys carry this water and unite as a single unit. Even the uncertainties and variations in rainfall are typical of the monsoons and are accepted as part of life in India. This shared experience of waiting for, welcoming, and depending on the monsoon creates a bond that unites all Indians.

Now let's move on to Question 3. Why does the rainfall decrease from the east to the west in Northern India? This happens because of the orographic effect and the direction of the monsoon winds. The south-west monsoon winds blow from the Bay of Bengal towards the northern plains. As they move from east to west, they lose moisture progressively. The eastern parts receive moisture first and hence receive more rainfall. By the time the winds reach the western parts like Rajasthan and Gujarat, they have lost most of their moisture, resulting in less rainfall. Additionally, the absence of significant mountain barriers in the western part of the plains allows the moisture-laden winds to pass through without giving up much rainfall.

Now let's move on to Question 4, which asks for reasons.

Reason (i): Seasonal reversal of wind direction takes place over the Indian subcontinent. This happens due to the differential heating of land and sea. In summer, the land heats up faster than the sea, creating a low-pressure area over the interior of Asia. This attracts the moist south-west monsoon winds from the Indian Ocean. In winter, the land cools down faster than the sea, creating a high-pressure area over northern India. This causes the dry north-east monsoon winds to blow from land to sea. This complete reversal of pressure and wind patterns twice a year is what gives India its monsoon climate.

Reason (ii): The bulk of rainfall in India is concentrated over a few months. This is because India's rainfall is primarily from the monsoon winds, which are seasonal. The south-west monsoon winds blow from June to September, bringing moisture from the Indian Ocean. During these four months, the winds dump most of their moisture as rainfall across the country. The rest of the year, the prevailing winds are dry trade winds that don't bring significant rainfall. That's why about 80-90% of India's annual rainfall occurs during the monsoon months.

Reason (iii): The Tamil Nadu coast receives winter rainfall. This happens because of the northeast monsoon winds. During winter, the northeast trade winds blow from land to sea. However, when these winds blow over the Bay of Bengal, they pick up some moisture. When they strike the Tamil Nadu coast, they blow from sea to land, bringing rainfall to this region. Additionally, during the retreating monsoon season, cyclonic depressions form over the Bay of Bengal and bring heavy rainfall to the Tamil Nadu coast. This is why Tamil Nadu receives most of its rainfall during October and November.

Reason (iv): The delta region of the eastern coast is frequently struck by cyclones. This happens because of the geographical location and the presence of the Bay of Bengal. During the retreating monsoon season (October-November), low-pressure systems form over the Andaman Sea and the Bay of Bengal. These intensify into cyclones and move towards the eastern coast. The deltas of the Godavari, Krishna, and Kaveri rivers are low-lying and densely populated, making them vulnerable to cyclone damage. These cyclones bring heavy rainfall, strong winds, and storm surges that cause widespread destruction.

Reason (v): Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone. These areas are drought-prone because they receive very less rainfall. Rajasthan and Gujarat are in the rain shadow area of the Aravalli mountains and receive scanty rainfall from the southwest monsoon. The leeward side of the Western Ghats is also in the rain shadow – when the monsoon winds strike the Western Ghats, they lose moisture on the windward side, so the leeward side receives very little rainfall. Additionally, these areas are far from the sea, so they don't get the moderating influence of oceans. The variability of rainfall is also high in these regions, making them susceptible to droughts.

Now let's move on to Question 5. Describe the regional variations in the climatic conditions of India with the help of suitable examples. India shows great regional variations in climate due to its vast size and varied topography. Let's discuss some examples:

Temperature variations: In summer, Rajasthan desert experiences temperatures around 50°C, while Pahalgam in Jammu and Kashmir has temperatures around 20°C. In winter, Drass in Jammu and Kashmir can go as low as minus 45°C, while Thiruvananthapuram has around 22°C.

Diurnal temperature range: The Thar Desert has a very high diurnal range – day temperature can be 50°C and night temperature 15°C. On the other hand, coastal areas like Kerala and Andaman Nicobar islands have minimal difference between day and night temperatures.

Rainfall variations: Mawsynram in Meghalaya receives over 400 cm of rainfall annually, while western Rajasthan receives less than 10 cm. The western coast receives heavy rainfall (over 400 cm), while the interior of the Deccan plateau receives moderate rainfall (around 100 cm).

Seasonal variations: Most of India receives rainfall from June to September (southwest monsoon), but the Tamil Nadu coast receives most of its rainfall during October and November (retreating monsoon).

Snowfall: Snowfall is restricted to the Himalayan region, while the rest of the country receives rainfall.

These variations create diverse climatic zones across the country – from hot deserts to wet forests, from snowy mountains to coastal plains.

Now let's move on to Question 6. Give an account of weather conditions and characteristics of the cold season. The cold weather season in India lasts from mid-November to February. Here are the main characteristics:

Temperature: December and January are the coldest months. Temperature decreases from south to north. Chennai has average temperatures of 24-25°C, while northern plains have 10-15°C. Days are warm but nights are cold. Frost is common in the north, and higher Himalayas receive snowfall.

Winds: The northeast trade winds prevail over the country. They blow from land to sea, making it a dry season for most parts. However, over the Tamil Nadu coast, these winds blow from sea to land, bringing some rainfall.

Weather: The weather is generally clear with low humidity and feeble winds. A weak high-pressure area develops over northern India, and winds blow from this area towards the south.

Western disturbances: Cyclonic disturbances from the Mediterranean Sea and western Asia bring winter rains to the northern plains. This rainfall, called 'mahawat', is important for rabi crops like wheat. The Himalayas receive snowfall, which feeds the rivers.

Peninsular region: The peninsular region doesn't have a well-defined cold season due to the moderating influence of the sea. Temperature variations are minimal.

Now let's move on to Question 7. Give the characteristics and effects of the monsoon rainfall in India. The characteristics of monsoon rainfall are:

Seasonal: Monsoon rainfall occurs primarily from June to September, accounting for 80-90% of annual rainfall.

Unpredictable: The monsoon is irregular in its arrival, retreat, and distribution. It can cause floods in one area and drought in another.

Breaks: The monsoon has wet and dry spells. Rain doesn't occur continuously; there are breaks of a few days.

Orographic effect: The Western Ghats receive very heavy rainfall (over 250 cm) on the windward side, while the leeward side (rain shadow) receives less rainfall.

Spatial variation: Rainfall decreases from east to west in the northern plains. Northeastern India receives the highest rainfall.

Cyclonic disturbances: Tropical depressions from the Bay of Bengal influence the amount and duration of rainfall.

The effects of monsoon rainfall are:

Agricultural: Monsoon rains are crucial for Indian agriculture. About 60% of India's cultivated land depends on monsoon rains for irrigation. Kharif crops like rice, cotton, and soybeans require monsoon rainfall.

Economic: The Indian economy is heavily dependent on the monsoon. A good monsoon leads to good harvests and economic growth, while a poor monsoon can cause drought and economic slowdown.

Water resources: Monsoon fills rivers, dams, and groundwater reserves, providing water for drinking, irrigation, and hydroelectric power.

Floods and droughts: Irregular monsoon can cause floods in some areas and droughts in others, affecting life and property.

Cultural: The monsoon influences Indian festivals, culture, and way of life. Festivals like Teej, Onam, and Ganesh Chaturthi are celebrated during the monsoon season.

Now let's discuss the map skills. On an outline map of India, show the following:

Areas receiving rainfall over 400 cm: These include the western coast (especially the Konkan and Malabar coasts), the Western Ghats, and northeastern India (especially Meghalaya, Assam, and Arunachal Pradesh). Mawsynram and Cherrapunji in Meghalaya are the wettest places.

Areas receiving less than 20 cm of rainfall: These include western Rajasthan, parts of Gujarat, and the Ladakh region.

The direction of the south-west monsoon over India: The monsoon winds enter India from the southwest, from the Arabian Sea and the Bay of Bengal. They move from the coastal areas towards the interior, covering most of the country by early July.

Now let's discuss the project and activity questions.

For the first project, you need to find out which songs, dances, festivals, and special food preparations are associated with certain seasons in your region. For example, Bihu is celebrated in Assam during spring, Onam is celebrated in Kerala during the monsoon/harvest season, and various harvest festivals are celebrated across India according to the monsoon cycle. You should examine if they have commonality with other regions of India.

For the second project, you need to collect photographs of typical rural houses and clothing of people from different regions of India. Then examine whether they reflect any relationship with the climatic condition and relief of the area. For example, houses in Rajasthan have thick walls and flat roofs, houses in heavy rainfall areas have sloping roofs, and houses in flood-prone areas like Assam are built on stilts.

Now let's work through the "For Doing It Yourself" section with the table.

First, let me explain what we need to do. In Table I, we have average mean monthly temperatures and amounts of rainfall for 10 representative stations. We need to study this table and answer various questions.

Looking at the table, we can see that each station has latitude, altitude, monthly temperatures, and monthly rainfall data.

Now let's answer the questions:

Question 2(i): Re-arrange the 10 stations in two different sequences according to their distance from the equator. The station closest to the equator (lowest latitude) would be Thiruvananthapuram (8°29'N), then Bengaluru (12°58'N), Chennai (13°4'N), Mumbai (19°N), Nagpur (21°9'N), Kolkata (22°34'N), Shillong (24°34'N), Jodhpur (26°18'N), Delhi (29°N), and Leh (34°N).

According to their altitude above mean sea level, from lowest to highest: Mumbai (11m), Chennai (7m), Kolkata (6m), Delhi (219m), Jodhpur (224m), Nagpur (312m), Bengaluru (909m), Thiruvananthapuram (61m), Shillong (1461m), and Leh (3506m). Wait, let me re-order this correctly from lowest to highest altitude: Chennai (7m), Mumbai (11m), Kolkata (6m), Delhi (219m), Jodhpur (224m), Nagpur (312m), Thiruvananthapuram (61m), Bengaluru (909m), Shillong (1461m), Leh (3506m).

Question 3(i): Name two rainiest stations. Looking at the annual rainfall column, Shillong receives 225.3 cm, and Mumbai receives 183.4 cm. So Shillong and Mumbai are the two rainiest stations.

Question 3(ii): Name two driest stations. Leh receives only 8.5 cm of rainfall, and Jodhpur receives 36.6 cm. So Leh and Jodhpur are the driest stations.

Question 3(iii): Two stations with most equable climate. Equable climate means minimal variation in temperature throughout the year. Looking at the temperature data, Thiruvananthapuram and Shillong have relatively constant temperatures throughout the year. Thiruvananthapuram ranges from about 27°C to 33°C, and Shillong ranges from about 20°C to 30°C. So these two have the most equable climate.

Question 3(iv): Two stations with most extreme climate. Extreme climate means very high variation in temperature between summer and winter. Delhi and Jodhpur have extreme climates. Delhi ranges from about 14°C in January to about 33°C in June, and Jodhpur ranges from about 25°C in January to about 33°C in May. So these have the most extreme climate.

Question 3(v): Two stations influenced by retreating monsoons. The retreating monsoon affects the eastern coast, particularly Tamil Nadu. Looking at the data, Chennai receives maximum rainfall in October and November (30.6 cm and 35.0 cm respectively), which is during the retreating monsoon. So Chennai is definitely influenced by retreating monsoons. Another station could be Kolkata, which also receives some rainfall during the retreating monsoon period.

Question 3(vi): The two hottest stations in the months of February, April, May, and June. For February, the hottest stations would be those with highest temperatures – looking at the data, Thiruvananthapuram has 26.7°C and Mumbai has 24.4°C. For April, the hottest would be Nagpur (30.0°C) and Delhi (30.0°C). For May, the hottest would be Nagpur (33.3°C) and Delhi (33.3°C). For June, the hottest would be Delhi (33.9°C) and Jodhpur (32.5°C).

Now let's answer Question 4:

(i) Why are Thiruvananthapuram and Shillong rainier in June than in July? This is because of the timing of the monsoon. The southwest monsoon arrives at Thiruvananthapuram (Kerala) first, in early June, bringing heavy rainfall. By July, the monsoon has spread to other parts of the country, so the concentration of rainfall decreases at Thiruvananthapuram. Similarly, Shillong receives heavy rainfall in June when the monsoon winds directly strike the Khasi Hills. By July, the monsoon trough shifts, reducing rainfall at Shillong.

(ii) Why is July rainier in Mumbai than in Thiruvananthapuram? This is because of the orographic effect. Mumbai is on the windward side of the Western Ghats, and in July, when the monsoon is fully established, the moisture-laden winds strike the Western Ghats heavily, causing orographic rainfall. By July, Thiruvananthapuram is in the rain shadow area as the monsoon winds have advanced further north.

(iii) Why are southwest monsoons less rainy in Chennai? Chennai is on the eastern coast, and the southwest monsoon winds blow from the west. The Western Ghats block the moisture-laden winds, so Chennai receives less rainfall from the southwest monsoon. Chennai receives most of its rainfall from the northeast monsoon (retreating monsoon) and cyclonic disturbances.

(iv) Why is Shillong rainier than Kolkata? Shillong is located on the southern ranges of the Khasi Hills, which force the moisture-laden monsoon winds to rise, causing heavy orographic rainfall. Kolkata is on the plain, so it doesn't receive as much orographic rainfall. Shillong receives about 225 cm of rainfall, while Kolkata receives about 162 cm.

(v) Why is Kolkata rainier in July than in June unlike Shillong which is rainier in June than in July? This is because of the movement of the monsoon trough. In June, the monsoon is just arriving and the trough is still over the southern parts. By July, the monsoon trough moves northwards and becomes established over the northern plains, bringing more rainfall to Kolkata. Shillong, on the other hand, receives maximum rainfall when the monsoon first arrives in June. By July, as the trough moves north, the rainfall at Shillong decreases.

(vi) Why does Delhi receive more rain than Jodhpur? Delhi is closer to the Bay of Bengal and receives moisture-laden winds from both the Arabian Sea and the Bay of Bengal. Jodhpur is in the interior, far from the sea, and is in the rain shadow of the Aravalli hills. So Delhi receives about 67 cm of rainfall while Jodhpur receives only about 36.6 cm.

Now let's answer Question 5:

Why Thiruvananthapuram has equable climate? Thiruvananthapuram is located near the equator (8°29'N), so it receives direct sunlight throughout the year. Additionally, it is surrounded by the Arabian Sea on one side, which moderates the temperature. The sea breeze keeps the temperature stable. That's why Thiruvananthapuram has minimal variation in temperature throughout the year.

Why Chennai has more rains only after the fury of monsoon is over in most parts of the country? Chennai receives most of its rainfall during the retreating monsoon (October-November) because by that time, the southwest monsoon has withdrawn from most parts. At this time, cyclonic depressions form over the Bay of Bengal and bring rainfall to the Tamil Nadu coast. During the southwest monsoon, Chennai is in the rain shadow of the Western Ghats.

Why Jodhpur has a hot desert type of climate? Jodhpur is located in the Thar Desert region. It is far from the sea (continentality), so there's no moderating influence. It receives very little rainfall (about 36.6 cm annually). The days are very hot in summer and cold in winter, with a high diurnal range. These are characteristics of a desert climate.

Why Leh has moderate precipitation almost throughout the year? Leh is located in a cold desert region at high altitude (3506m). It receives very little rainfall (only 8.5 cm annually) throughout the year because it's in the rain shadow of the Himalayas. The precipitation that does occur is mostly in the form of snow during winter.

Why in Delhi and Jodhpur most of the rain is confined to nearly three months, while in Thiruvananthapuram and Shillong it is almost nine months of the year? This is because of the nature of the monsoons. Delhi and Jodhpur receive rainfall primarily from the southwest monsoon, which is active from June to September – about 3-4 months. Thiruvananthapuram and Shillong receive rainfall from multiple sources – the southwest monsoon, retreating monsoon, and cyclonic disturbances. Shillong also receives rainfall from the northeast monsoon and local orographic effects. That's why these places receive rainfall for most of the year.

Now, students, I want you to notice something very important. Even though different parts of India receive different amounts of rainfall at different times, the monsoons still provide a very strong framework lending overall climatic unity to the whole country. The arrival of the monsoon is awaited by all Indians, the agricultural calendar revolves around the monsoon, and the rhythm of seasons is defined by the monsoon. This is the unifying bond that connects all of India.

Now, students, let me give you a complete summary of everything we've learned in this chapter.

In this chapter on Climate, we learned that:

Climate is the sum total of weather conditions over a long period, while weather is the state of the atmosphere at any point of time. The elements of weather and climate are temperature, atmospheric pressure, wind, humidity, and precipitation.

India has a monsoon type of climate, characterised by seasonal reversal of winds. The word "monsoon" comes from the Arabic word "mausim" meaning season.

There are six factors that control India's climate: latitude, altitude, pressure and wind system, distance from the sea (continentality), ocean currents, and relief features.

India experiences four main seasons: the cold weather season (winter), the hot weather season (summer), the advancing monsoon (rainy season), and the retreating monsoon (transition season).

During winter, the northeast trade winds blow from land to sea, bringing dry weather to most parts. Western disturbances from the Mediterranean Sea bring winter rains to the northern plains, important for rabi crops.

During summer, temperatures rise, especially in the northwestern parts. The loo – hot, dry winds – blow during the day. Pre-monsoon showers occur in Kerala and Karnataka, called mango showers.

The southwest monsoon arrives by early June, bringing heavy rainfall to most parts of the country. The western coast and northeastern India receive heavy rainfall, while western Rajasthan receives scanty rainfall. The monsoon has breaks – wet and dry spells. The monsoon is unpredictable and can cause both floods and droughts.

During the retreating monsoon (October-November), the monsoon withdraws from the northern plains. The weather becomes oppressive due to high temperature and humidity, known as October heat. Cyclones from the Bay of Bengal affect the eastern coast, especially the deltas of Godavari, Krishna, and Kaveri.

Rainfall distribution varies greatly – over 400 cm in the northeast and western coast, less than 10 cm in western Rajasthan and Ladakh. Rainfall decreases from east to west in the northern plains.

The monsoon is a unifying bond for India. It binds the country together by providing water for agriculture, influencing the agricultural calendar, festivals, and the daily life of people throughout the country.

Students, this brings us to the end of our lesson on Climate. I hope you now have a clear understanding of India's climate, its variations, and its importance in our daily lives. Remember, climate affects everything from the food we eat to the houses we live in. Understanding climate helps us understand our country better. Thank you for your attention, and I'll see you in the next lesson!