Climate: Notes Class 9 NCERT Geography

Climate Notes Class 9 NCERT Geography: The Notes of the chapter ‘Climate’ covers the topics – Weather and Climate, the Seasons, climatic Control and Factors affecting India’s Climate, the Indian Monsoon, the Onset of the Monsoon and withdrawal, seasons, distribution of rainfall and Monsoon as a Unifying Bond.

Climate Class 9 geography – Weather, seasons and climate

Different Concepts

Weather

  • Weather refers to the state of the atmosphere over an area at any given point of time i.e. variations and fluctuations may be observed over short period of time from minute to minutes and hours to hours i.e. the day-to-day changes that we experience are referred to as Weather.
  • The elements of weather are temperature, atmospheric pressure, winds, humidity and precipitations.
  • Common weather patterns observed are – sunshine, clouds, winds, snow, fog, rain.
  • The study of weathers is called meteorology.

Climate

  • It is the average of weather patterns of an area lasting for a longer time of over 30 years. variations are there but some common pattern is almost same throughout the mentioned longer duration of 30 or more years.
  • Elements of climate are same as the elements of weather – wind, temperature, air pressure, precipitation and moisture.
  • The two important elements of climate are temperature and precipitation varying from place to place and season to season.
  • Climate is also affected by some other factors like location and relief features.
  • Based on climatic differences, the world can be divided into a number of climatic regions. Each climatic region has its own characteristic vegetation and wildlife. The climatic conditions also influence the lifestyles of the people living in these regions.
  • India has monsoon type climate.
  • The study of climate is called climatology.

Seasons

  • A year is divided into seasons based on general weather conditions lasting through an average period of three months.
  • Seasons are affected by the revolution of the earth and its changing distance from the sun which is responsible for the availability of sunshine on any location on the earth.
  • There are four seasons – summer, winter, spring and autumn but all are not observed everywhere on the earth.
  • The northern hemisphere and the southern hemispheres have opposite seasons.

Monsoon

  • The word monsoon is derived from the Arabic word ‘mausim’ which literally means seasons.
  • Monsoon refers to the seasonal reversal in the wind direction during a year.
    India has monsoon type climate.
  • In Asia this type of climate is mainly found in the south and the south-east Asia.

Regional Variations in Climatic Conditions in India

Temperature

  • Seasonal contrast is more and extreme (Continentality) in the interior of the country (away from the sea) than in the coastal areas where equable climate is found with less contrast in summer and winter seasons.
  • 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.
  • On a winter night, temperature at Drass in Ladakh may be as low as minus 45°C. On the other hand, in Thiruvananthapuram, it may have a temperature of 22°C.

Precipitation

  • There are variations not only in the form and types of precipitation but also in its amount and the seasonal distribution.
  • The annual precipitation varies from 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan.
  • Precipitation is mostly in the form of snowfall in the upper parts of the Himalayas but it rains over the rest of the country.
  • Most parts of the country receive rainfall from June to September but some parts like the Tamil Nadu coast gets most of its rains during October and November.
  • There is decrease in rainfall generally from east to west in the northern plains.

Effect of seasonal variations on lives of people

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.



Climatic Controles

Latitude: Due to the curvature of the earth insolation or sun rays are not equally focused on every latitude and air temperature decreases from the equator towards the poles.

Altitude: At higher altitudes, the atmosphere becomes less dense and temperature decreases with increasing altitudes. Hills are cooler during summers, e.g., climate of Shimla is cooler than that of Delhi.

The pressure and wind system: It depends on the latitude and altitude of the place. Thus, it influences the temperature and rainfall pattern.

Distance from the sea: As the distance from the sea increases, its moderating influence decreases and the people experience extreme weather conditions known as continentality.

Ocean currents: Any coastal area with warm or cold currents flowing past it will be warmed or cooled if the winds are onshore.

Relief: High mountains act as barriers for cold or hot winds. They may also cause precipitation if they are high enough and lie in the path of rain-bearing winds. The leeward side of mountains remains dry.


Factors Affecting Climate of India

Latitude

  • The Tropic of Cancer passes almost from the middle of the country.
  • Almost half of the country, lying south of the Tropic of Cancer, belongs to the tropical area.
  • All the remaining area in the north of the Tropic of Cancer lies in the sub-tropical area. Therefore, India’s climate has characteristics of tropical as well as sub-tropical type of climate.

Altitude- India’s climatic controls class 9 geography

Altitude

  • India has mountains to the north which have an average height of about 6,000 metres.
  • The Himalayas prevent the cold winds from Central Asia, from entering the subcontinent.
  • It is due to these mountains that the Indian subcontinent experiences comparatively milder winters as compared to Central Asia.

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