Atmospheric Circulation and Weather Systems Test - 1

Thunderstorms are caused by intense convection on moist hot days. 

The vertical pressure gradient force is much larger than that of the horizontal pressure gradient. But, it is generally balanced by a nearly equal but opposite gravitational force.

It is greatest at the surface and its influence generally extends upto an elevation of 1 - 3 km.

Air pressure is measured with the help of a mercury barometer or the aneroid barometer. 

The warm water of the central Pacific Ocean slowly drifts towards the South American coast and replaces the cool Peruvian current. Such appearance of warm water off the coast of Peru is known as the El Nino.

The pressure gradient is strong where the isobars are close to each other and is weak where the isobars are apart.

Near the equator, from about 5° north and 5° south, the northeast trade winds and southeast trade winds converge in a low pressure zone known as the intertropical convergence zone (ITCZ).

A cell in the tropics is called the Hadley Cell.

This causes an accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30° N and S latitudes. 

A monsoon is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscillation of the Intertropical Convergence Zone (ITCZ) between its limits to the north and south of the equator.