Their direction of movement is NE to SW in the northern hemisphere and SE to NW in the southern hemisphere.These are known as Northeast trade winds in the northern hemisphere and southeast trade winds in the Southern hemisphere.These flow from subtropical high-pressure belts to equatorial low-pressure belts in both hemispheres north and south.They blow in the same direction throughout the year. These are also called invariable or planetary wind systems because they blow over larger areas of the earth. The frictional force is effective up to a height of a few thousand meters only. Friction is least above smooth oceanic surfaces. The amount of friction is an outcome of surface irregularities and the orientation of natural landforms. Friction force generated by surface: It is a restraining force on the flow of the wind.They are deflected to the right (concerning their source) in the northern hemisphere and the left in the southern hemisphere. Coriolis force/deflection force: The force that deflects the direction of the wind is called deflection force.The velocity of wind is directly proportional to pressure gradient force.

The flow is from high pressure to low pressure and it is at right angles to isobars.

Pressure gradient force: This force provides initial flow and direction to the wind.

The horizontal movement of air is described as the wind caused by the heating of the sun and the rotational movement of the earth.įlow and direction are controlled by the following geographical factors and processes: What are winds? How do winds originate? What are the classifications and types? Read to know more.

Define valley breeze