Atmospheric Circulation and Weather Systems Test - 3

Due to gravity, the air at the surface is denser and hence has higher pressure. 

The rotation of the earth about its axis affects the direction of the wind. This force is called the Coriolis force after the French physicist who described it in 1844. 

Horizontal distribution of pressure is studied by drawing isobars at constant levels.

Near the equator the sea level pressure is low and the area is known as equatorial low. 

The vertical pressure gradient force is much larger than that of the horizontal pressure gradient.

The atmospheric pressure is expressed in units of millibar. At sea level, the average atmospheric pressure is 1,013.2 millibar. 

Frictional Force affects the speed of the wind. It is greatest at the surface and its influence generally extends up to an elevation of 1 - 3 km. Over the sea surface, the friction is minimal.

 If an air mass is fully lifted above the land surface, it is called the occluded front.

When two different air masses meet, the boundary zone between them is called a front. 

When isobars are straight and when there is no friction, the pressure gradient force is balanced by the Coriolis force and the resultant wind blows parallel to the isobar. This wind is known as the geostrophic wind.