Define the term : Trade wind.

Explanation

The equatorial and polar regions of the earth receive unequal solar heat.
Air at the earth.s surface near the equator is hot while the air in the upper atmosphere of the poles is cool.
In the absence of any other factor, a convection current would be set up.
The air at the equatorial surface rising and moving out towards the poles, descent and stream in towards the equator.
The rotation of the earth, however, modifies this convection current. Because of this, air close to the equator has an eastward speed of 1600 km/h, while it is zero close to the poles.
As result, the air descends not at the poles but at `30^(@)N` (North) latitude and returns to the equator. This is called trade wind.
The steady surface wind on earth blow in from northeast towards the equator, the so called is trade wind.