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Table of contents
In this blogpost, we will learn about following aspects of climate:
1. Variation and Contrasts in Climate: The climate in India varies in different regions and has contrasts. Some places are very hot in summer and extremely cold in winter, while others remain hot throughout the year. Coastal areas have a moderate climate because of the influence of the sea.
2. Classification: Climate is classified into different types based on temperature and rainfall patterns. We will explore these classifications.
3. Tropical Rainy Climate: India has a tropical monsoon climate, which means it experiences heavy rainfall during the monsoon season. We will learn about the characteristics of this climate.
4. Dry Climate Group: Some regions in India have a dry climate with very little rainfall. We will understand the features of this climate group.
5. Humid Sub-tropical Climate Group: Certain areas in India have a humid sub-tropical climate, which is characterized by hot and humid summers and mild winters. We will explore this climate group in detail.
6. Mountain Climate: The climate in the mountainous regions of India is unique and different from other areas. We will discover the characteristics of this climate.
Introduction
Climate refers to the long-term average weather conditions over a considerable period of time. It is influenced by the sun’s radiation on the Earth’s surface and atmosphere. Climate can be understood by looking at the average temperature and rainfall patterns throughout the year. It includes not only the average conditions but also the variations that occur from day to day and year to year.
India has a tropical monsoon climate overall, but there are significant regional variations in rainfall and temperature. Rainfall varies more than temperature across the country. India receives ample sunshine from the tropical sun and abundant rainfall from the monsoon season, which are crucial factors for the people of India.
1. Variation and Contrasts in Climate
The climate in India is influenced by various geographical factors, leading to a complex climate pattern. Here are some important factors:
a) Temperate conditions
Places located north of the Tropic of Cancer have a continental climate. Summers are very hot, and winters are extremely cold. For example, Rajasthan can experience temperatures as high as 50ºC in summer, while places like Dras near Kargil can drop to -40ºC in winter.
Places situated south of the Tropic of Cancer, closer to the equator, remain hot throughout the year, with average temperatures ranging from 25ºC to 27ºC. They do not have a distinct winter season. For instance, Bangalore in the south.
Places along the east-west coastline of India have an equable or maritime climate due to the moderating effect of the sea. The temperature remains moderate throughout the year, neither too hot nor too cold. Examples of such places are Mumbai, Goa, and Chennai. Unlike the interior regions, the coastal areas experience a smaller annual temperature range, usually about 3ºC to 5ºC.
b) Rainfall
India experiences varying levels of annual rainfall. Mawsynram, a station in Meghalaya, receives the highest annual rainfall in the world, around 1167cm. In contrast, the Thar Desert in Rajasthan receives less than 25cm of rainfall.
The monsoon rains in India can be unpredictable and sometimes cause floods or droughts in different regions. The two coasts of the Indian peninsula have opposite monsoon wind patterns. The western coast receives the heaviest rainfall during the Southwest Monsoon in June, while the eastern coast remains relatively dry in summer but receives maximum rainfall in winter.
In the Himalayan regions at higher altitudes, heavy snowfall occurs in winter, while places in South India, even at higher altitudes, never experience snowfall due to their proximity to the equator.
c) Temperature
This significant contrast in climate is a result of several factors affecting temperature:
1. Location
The Tropic of Cancer divides India into a temperate or subtropical North and a tropical South. The northernmost part of the subcontinent is occupied by high mountains, experiencing an extreme or continental climate. The southern peninsula, surrounded by the Arabian Sea, Indian Ocean, and Bay of Bengal, has a more equable climate. Generally, temperature increases from north to south.
2. Influence of the Himalayas:
a) The Himalayan range blocks the cold winds from Siberia, keeping them from reaching the Indian subcontinent.
b) The Himalayas intercept the southwest monsoon winds, causing heavy rainfall in the northeast and Indo-Gangetic plain.
3. Altitude
Temperature decreases with increasing altitude. For every 166 meters of ascent, the temperature drops by about 1ºC. Therefore, places at higher altitudes are cooler compared to those in the plains.
4. Distance from the sea
Interior regions experience extreme (continental) climates, while coastal areas have a more moderate climate due to the land breeze and sea breeze caused by differential heating and cooling of land and sea.
5. Western disturbances and tropical cyclones
In winter, low-pressure systems called western disturbances bring rain to northwest India. These disturbances originate from the Mediterranean Sea, cross Iraq, Afghanistan, and Pakistan, intensify over North West India, and move eastward, resulting in rain in Punjab and Haryana and snowfall in the Himalayan region.
During summer, the east coast of India and coastal areas of Bangladesh are influenced by tropical depressions, which can cause significant damage.
6. Upper air currents or jet streams
The upper air currents, known as jet streams, in the upper layers of the atmosphere can impact the monsoon. Research is ongoing to understand the extent of their influence on monsoons.
2. Classification
There are different ways to classify the climate regions of India. These classifications help us understand the different types of climates found in the country. Here are some methods of classification:
Genetic methods:
These methods focus on the causes of climate. They consider factors like air mass types and weather disturbances. They aim to understand the reasons behind climate patterns.
Empiric methods:
These methods focus on the effects of climate. They look at climate zones based on factors like plant hardiness, evaporation, and rainfall. One popular empiric classification is the Koppen climate classification, which was developed to identify climate types associated with different ecosystems.
In the 19th century, Blanford was the first to classify the climatic regions of India. Dr. L. Dudley Stamp also classified the Indian climate based on temperature and rainfall, which are easily understood factors.
Thornthwaite, in 1931, viewed plants as meteorological instruments to measure climate characteristics. He classified climate based on the viewpoint of plants.
Dr. R.L. Singh presented his climatic divisions of India in 1971. He divided the country into 10 climatic divisions based on temperature conditions in the hottest and coldest months, as well as average annual rainfall.
However, one limitation of these classification schemes is that they often create distinct boundaries between climate zones, whereas in nature, climate properties usually transition gradually.
India experiences a wide variation in climate due to its large size. The country can be divided into four major climate groups, which can be further subdivided into seven climatic types.
3. Tropical rainy climate
This climate group includes regions that have consistently high temperatures, with temperatures not dropping below 18°C even in the coolest month. There are two types of climates within this group:
Tropical monsoon rain forest
This climate is found in the west coastal plain, the Sahyadris, and parts of Assam. The temperature remains high throughout the year, with winter temperatures not falling below 18.2ºC and rising to 29ºC in April and May, the hottest months. These regions experience heavy rainfall, with average annual rainfall exceeding 200 cm.
The southwest monsoon arrives early and lasts longer here. The region is known for its evergreen forests and plantation agriculture, including crops like tea, coffee, and spices.
Tropical wet and dry or savanna climate
This climate is experienced in most parts of the Indian peninsula, except for the semi-arid zone on the leeward side of the Sahyadris. It has long dry periods during winter and early summer, with temperatures above 18°C. Summers are very hot, with temperatures in the interior low-level areas reaching above 45°C in May.
The rainy season occurs from June to September, with annual rainfall between 75 and 150 cm. This region is characterized by savanna vegetation, and a variety of crops are cultivated, both with and without irrigation.
4. Dry climate group
This group consists of regions where the rate of evaporation of water is higher than the rate of moisture received through precipitation. It is further divided into three climate types:
Tropical semi-arid steppe climate
This climate is found in the rain-shadow belt running southward from central Maharashtra to Tamil Nadu, on the leeward side of the Sahyadris and Cardamom Hills. These regions experience low and uncertain rainfall, making them prone to famines. The area receives minimal rainfall, ranging from 40 to 75 cm annually. The natural vegetation consists mostly of grasses, and the climate is suitable for dry farming and livestock rearing.
Tropical and subtropical desert
Most of western Rajasthan falls under this climate type, characterized by scanty rainfall. Rainfall in this region is less than 30 cm and is mostly caused by cloud bursts during the monsoon season. The rainfall is erratic, and some areas may not receive rainfall for several years.
Summers are extremely hot, with temperatures reaching highs of 50°C, while winters can be cold with temperatures dropping below freezing. The Thar Desert and surrounding areas experience this desert climate, making it sparsely populated.
Tropical and subtropical steppe:
This climate type is found in the region east of the tropical desert, stretching from Punjab and Haryana to Kathiawar. It is a transitional climate between tropical desert and humid subtropical climates. The annual rainfall ranges from 30 to 65 cm and is mostly received during the summer monsoon season. Summers can be hot, with temperatures up to 40°C. The vegetation mostly consists of short coarse grass, and some crops like jowar and bajra are cultivated. The Thar Desert in western Rajasthan also falls under this climate type, characterized by a typical desert climate.
5. Humid subtropical climate group
In regions with this climate, the temperature during the coldest months ranges from 18 to 0°C. There is one subdivision of this climate type in India.
Humid subtropical with dry winters
This climate is found in the foothills of the Himalayas, Punjab-Haryana plain near the Himalayas, Rajasthan east of the Aravalli range, Uttar Pradesh, Bihar, and the northern part of West Bengal and Assam. Most of the rainfall occurs in the summer, ranging from about 65 cm in the west to 250 cm near the Himalayas in the east. Winters are mostly dry due to the winter winds blowing down the lowlands of North India towards the Bay of Bengal. Summers are hot, with temperatures reaching up to 46°C in the lowlands. May and June are the hottest months. Winter months are dry with weak winds. Frost occurs for a few weeks in winter. The difference in rainfall between the east and the west results in varying natural vegetation and crops.
6. Mountain climate
In the Himalayan mountains, the temperature decreases by 0.6°C for every 100 meters of altitude, leading to a variety of climates ranging from almost tropical in the foothills to tundra-like conditions above the snow line. There are sharp temperature contrasts between sunny and shady slopes, high temperature differences within a day, temperature inversions, and variable rainfall based on altitude.
The northern side of the western Himalayas, also known as the trans-Himalayan belt, is arid, cold, and often windy. Vegetation is sparse and stunted due to low rainfall and severe winter cold. Most of the snowfall occurs in late winter and spring. The southern side of the mountains is protected from cold winds during winter.
The leeward side receives less rainfall compared to the exposed slopes. Areas between 1070 and 2290 meters receive the heaviest rainfall, which decreases rapidly above 2290 meters. The higher parts of the Great Himalayan range experience heavy snowfall from December to February. There is a significant temperature difference within a day.
The states of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Arunachal Pradesh, and Sikkim have this type of climate.
Conclusion:
The climate of a country involves studying temperature, rainfall, atmospheric pressure, wind direction, and wind speed over a long period of time.
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