NCERT Class 7 Geography Chapter 4: Air Completes Notes Part 3

Glide to success with Doorsteptutor material for IMO : fully solved questions with step-by-step explanation- practice your way to success.

Download PDF of This Page (Size: 303K)

Get the Video tutorial on this topic at: Air

Wind

Loading Video

Winds - Coriolis Effect, 3 Planetary and Local Winds in Climatology

Now what are wind? Wind is a movement of air as I said from high pressure to low pressure so that is what I classify as wind. Now wind can be either be gentle in nature or strong. Gentle wind would be kind of calm weather phenomena that would be brought but strong wind would lead to stormy condition. It would also lead to a kind of strong winds and would also be seen in the phenomena associated with tsunami or all those would be strong winds.

Now when we classify winds, three basic categories of winds.

  1. Permanent winds: Permanent winds which flow into a particular throughout the air so throughout the air they would same direction.

Image of Wind

Image of Wind

Loading Image

Understanding the concept of three basic winds you have the region that grew the winds that goes into the tropical region is known as the trade wind. Next to the trade winds you have the westerlies, towards the poles, the winds that blows from pool are known as easterlies. They are the permanents winds and they move in a particular direction throughout the year.

  1. Seasonal winds: Seasonal winds occur due to the changes in the direction of the wind and those change of direction is clearly explained by monsoon phenomenon in India.

  2. Local Winds: I can say the hot wind that glow in the summer months in the regions of Rajasthan or dry arid areas in India is known as “Loo” that a kind of local winds. Land breeze and Sea Breeze is an example of local wind.

Image of local Wind

Image of Local Wind

Loading Image

Moisture

Loading Video

Precipitation - 4 Categories, Mechanism, Bergeon Process & Measurement

Now next start with concept that is moisture and precipitation. What happens as you have the air mass that heats up from the land. When the air mass is being heated up it becomes hot and it rises when it rise it leads to a saturation point and there is condensation that occurs, condensation leads to formation of clouds, now this clouds fall down as rainfall and you have process of rainfall.

What is Moisture?

Moisture is the amount of water that is present into air mass. If the air is fully laden with moisture we call it a kind of humid day so humid would be day where you have air parcels which includes lot of moisture now there are three types of rainfall.

Image of Moisture

Image of Moisture

Loading Image
  1. Cyclonic Rainfall: that occurs due to the formation of Cyclone or depression that occurs.

  2. Tropical Cyclonic

  3. Temperature Cyclonic (has been discussed in separate video)

  4. Relief Rainfall: We also call it Orographic rainfall. The moist laden clouds that move and reach a saturation point, strike with a mountain surface and pour down as rainfall. Reason where they cause rainfall is known as the windward side and the region which is left comparatively dry is known as the leeward side. So generally it occurs when you have set of cloud that heats up mountain area.

  5. Convectional rainfall: Convectional rainfall is normal process of the heating, formation of cloud and then warm air rises up. You have formation of cloud, you have saturation that come into place and finally you have downpour.