Wind

Wind Part-1

What is wind?
Wind is the flow of air.

What is the direction of flow of wind?
Wind flows from high pressure area to low pressure area.

How do low pressure area and high pressure area get created?
It is simple to understand. Suppose air at a location 'A' gets heated. The warm air being lighter will rise upwards to new location 'B'. The location 'A' is less crowded as far as air quantity is concerned. So location 'A' is low pressure location or area. Whereas location 'B' will contain more air quantity due to addition of new air quantity from location 'A'. Thus location 'B' is high pressure location or area.
Now we have two locations or areas. One is low pressure location/area and the other high pressure location/area. As we know, wind flows from higher pressure to lower pressure, so in this case wind will flow from location 'B' to location 'A'.

Summary:

• Wind flows from high pressure zone to low pressure zone like water (water flows from high pressure to low pressure.
•   Heating or warmth to air causes air to rise leaving low pressure zone
• Warm air rises upwards and thus causes high pressure at new location  

This simple concept will help in understanding most of the topics of wind.

Now we will learn about local wind and permanent wind.

Local wind includes:

1. Sea breeze and land breeze
2. Monsoon
3. Cyclones and Anticyclone
4. Super Cyclone

Before explaining Local wind, let me ask a simple question.

Why does water take longer than land to get heated and to cool down?

It can be verified experimentally easily. 

Reasons:

1. water is a slow conductor of heat as compared to land.
2. water has high heat capacity as compared to soils (land)

These two reasons explain why water takes longer than land to get heated and to cool down. Whichever reason you are comfortable at, you can use. The purpose is not to accept any fact without proper reasoning.

Sea breeze: 

During day time, land gets heated faster as compared to sea (sun rays heat quickly land as compared to water due to reasons explained above. Land conducts heat relatively better than water. Further heat capacity that is capacity to retain heat is less for land as compared to water.). Warm air above land rises upwards and thus creating low pressure on the surface of land. Similarly, air above see is relatively cooler (as water takes longer time to get heated as compared to land) and hence high pressure is created there. To equalize the pressure, air flows from high pressure to low pressure. This is known as sea breeze. Thus sea breeze brings down temperature in coastal areas during day time.

Land Breeze:

  

What happens during night? Air near land gets cooler, and hence a zone of high pressure. Further air above sea will be relatively warmer than land, and hence at lower pressure. So air flows from higher pressure to lower pressure, that is, from land to the sea. This is known as land breeze.

Pressure difference can easily explain monsoon, cyclones and anticyclones. In the second part we will discuss monsoon and cyclones in detail.