Climate Class 9 Notes

Climate Class 9 Notes: The chapter “Climate” in Class 9 Geography helps students understand the climatic conditions of India, the factors affecting climate, the major seasons, and the role of the monsoon. These notes simplify concepts and offer a clear summary to aid in quick revision.

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Climate: Climate is a long-term pattern of temperature, humidity, wind, and precipitation. Climate is dependent on a combination of factors like the orbit around the sun, the tilt of the earth’s axis, and the presence of oceans and land masses.

Weather: Weather is a short-term condition of the atmosphere in a particular place at a particular time. Weather is dependent on temperature, humidity, wind speed, and direction. Weather can change quickly and influence the high and low pressure system.

There are several elements that are used to describe weather:

Temperature: How hot or cold the air is.
Humidity: The amount of moisture in the air.
Wind: The movement of air across the surface of the Earth.
Precipitation: Rain, snow, hail, or sleet falling from clouds.
Pressure: The force per unit area exerted by the weight of the atmosphere.
Cloud cover: How much of the sky is covered by clouds.
Visibility: The distance that one can see clearly.

India has three main seasons: summer, monsoon (or rainy), and winter.

Summer: In India summer is typically hot and dry and lasts from March to June. In summer temperatures can rise above 40 in many areas.
Monsoon: The monsoon brings heavy rainfall across the western coast and northeastern regions. The monsoon helps the farmer for agriculture.
Winter: In winter the temperatures are cold and the humidity is low. Northern parts of India can experience chilly weather, and southern regions remain relatively mild.

Climatic Controls

The climate of any place depends on different factors:

Latitude: The earth is curved, and every place gets a different amount of sunlight. Near the equator, they get more sunlight; due to more sunlight, the climate is hot, and near the poles, they get less sunlight due to the cold climate.
Altitude: In hill stations or in mountains, the air becomes thinner and holds less heat.
Pressure and Wind System: Winds and air pressure are different in different places of the world. This air pressure affects temperature and rainfall.
Distance from the Sea: If a place is near the sea, the temperature is more stable. If a place is far from the sea, it can be very hot in summer and cold in winter; this effect is called continentality.
Ocean Currents: Ocean water moves in long streams called currents. Warm currents can create heat in nearby places, and cold currents can create a cool climate in nearby places.
Relief Features: Mountains can block winds; if moist winds hit a mountain, then they rise up and cause rain or snow.

Factors Affecting India’s Climate

Latitude: The Tropic of Cancer passes through the middle of India from west (Rann of Kachchh) to east (Mizoram); because of this, India experiences both tropical climates (hot and humid) and subtropical climates (hot summers and cool winters).
Altitude: Northern India has high mountains like the Himalayas, and coastal areas are lower in height. Due to this factor, the Himalayas help to block icy winds from Central Asia.
Pressure and Winds:
- Surface Winds: Winds move from the southern Indian Ocean (high-pressure areas) to the Indian subcontinent (low-pressure areas). This wind is known as the Southwest Monsoon, which brings heavy rainfall.
- Upper Air Circulation: High-altitude winds steer weather systems and influence India’s seasonal climate patterns.
- Western Disturbances & Tropical Cyclones: Western disturbances come from the Mediterranean region and bring winter rainfall to North India. Tropical cyclones, originating over warm ocean waters, hit coastal areas and cause intense rainfall and storms.
- Jet Streams: These are narrow, fast-moving air currents high up in the atmosphere.

The Indian Monsoon

The Indian climate depends on monsoon winds. In summer the wind blows from the Indian Ocean, and in winter winds reverse and blow from land to sea.

The Indian monsoon is a seasonal weather pattern that affects the Indian subcontinent.
The Indian monsoon brings heavy rainfall, and it is between the months of June and September.
In the monsoon seasonlow pressure develops in India, and high pressure develops in the sea.
The Intertropical Convergence Zone moves north in summer and creates the monsoon over the Ganga plains.
Most air from the Indian Ocean rushed towards India, rose, cooled, and formed rain clouds.
The moving weather zone known as the ITCZ brings more rainy weather.
As the ITCZ moves over India, it brings moist air from the Indian Ocean, which rises and cools, resulting in the formation of clouds and rain.

The Onset of the Monsoon and Withdrawal

The monsoon season in India starts from the first week of June. The monsoon first arrives at Kerala.
The monsoon then divides into two branches: the Arabian Sea and the Bay of Bengal branches.
The Arabian Sea branch reaches Mumbai around 10th June, and the Bay of Bengal branch arrives in Assam in the first week of June.
Delhi receives the monsoon showers from the Bay of Bengal branch by the end of June.
In the month of July the western monsoon arrives in Uttar Pradesh, Panjab, Haryana, and eastern Rajasthan.
In mid-July the monsoon arrives in Himachal Pradesh and the rest of the country.

Withdrawal of the Monsoon

Withdrawal of the monsoon refers to the end of the monsoon season.
The withdrawal of the monsoon begins in the month of October and is completed by November.
The withdrawal of the monsoon can vary from year to year and from region to region.
In the time of withdrawal of the monsoon, the humidity is decreasing and the temperature is increasing.
The end of the monsoon season can have a significant impact on agriculture, the economy, and daily life.

The Seasons

4 main seasons can be identified in India:

The cold weather season (Winter)
The hot weather season (Summer)
The advancing monsoon (Rainy Season)
Retreating/Post Monsoons (The Transition Season)

1) The cold weather season (Winter)

The cold weather season, also known as winter, is a time of year when temperatures drop and the weather becomes colder. The cold weather season varies depending on the location, but it typically occurs between November and March in the Northern Hemisphere.

The cold weather season begins in the month of mid-November and lasts until February.
The coldest months of the winter season are December and January.
The average temperature in the Northern plains ranges between 10°C and 15°C, while in the Southern city of Chennai, on the Eastern coast, it is between 24°C and 25°C.
During the winter season the days are warm and nights are cold.
In the winter season snow falls in the Himalayan mountain range.
Most of the country remains dry due to the northeast trade winds, but rain may occur in Tamil Nadu and Southern Andhra Pradesh due to the winds picking up moisture from the Bay of Bengal.

2) The hot weather season (Summer)

The summer season is a hot weather season; in summer the temperatures rise and the weather becomes warmer. The duration of the hot weather season varies depending on the location but is basically between March and May in the Northern Hemisphere.

When the temperature rises, then the atmospheric pressure begins to drop.
One of the most distinctive features of Indian summer is loo, which refers to strong, gusty, hot, and dry winds. These winds can be dangerous if prolonged exposure occurs.
Pre-monsoon showers, also known as “mango showers,” may occur towards the end of the summer season and help with the early ripening of mangoes.

3) Advancing Monsoon (The Rainy Season)

The rainy season, commonly known as monsoon, brings an increase in rain and humidity. The monsoon typically occurs between June and September in the Northern Hemisphere.

Monsoon winds start to fade as the sun moves south.
The Northern Plains see clear skies and rising temperatures.
This season transitions from rainy to winter.
Cyclones form over the Bay of Bengal, bringing heavy rain to eastern coasts.
Areas like the Godavari, Krishna, and Kaveri deltas often get hit by storms.
Most of the rain falls on the Coromandel Coast during this period.

4) Retreating/Post Monsoons (The Transition Season)

The retreating or post-monsoon season, also known as the transition season, is the time when India shifts from the rainy monsoon months to cooler winter conditions. This usually happens between October and November.

During this period the southwest monsoon winds become weaker.
The weather becomes clear and dry.
Nights are cooler and pleasant, especially in northern India.
In the second half of October, temperatures start to drop quickly.
Tamil Nadu receives most of its rainfall during this season due to northeast monsoon winds.

Distribution of Rainfall

Parts of the western coast and northeastern India receive over 400 cm of rainfall annually.
Other areas, including western Rajasthan and parts of Gujarat, Haryana, and Punjab, receive less than 60 cm of rainfall annually.
The Deccan plateau and areas east of the Sahyadris also have low levels of rainfall.
Snowfall is limited to the Himalayan region.
The annual rainfall in India is highly variable from year to year.

Monsoon as a Unifying Bond

The monsoon acts as a unifying bond across India, connecting regions, cultures, and livelihoods. The monsoon helps farmers across India for irrigation. It is the backbone of Indian agriculture. Festivals like Onam in Kerala, Teej in Rajasthan, and Rath Yatra in Odisha are timed with the monsoon arrival, which reflects its deep cultural significance. The monsoon rejuvenates rivers, forests, and wildlife and influences biodiversity. Industries like hydroelectric power plants, fishing, and tourism are shaped by the monsoon.

Social Science Class 9 Notes

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