9. Wind

Air moves both horizontally and vertically. The wind is the vertical movement, and Air current is the horizontal movement of air. The wind always flows from the region of high pressure to that of the low-pressure region. Unlike other elements, gusts and eddies can only be felt and not seen. Winds are named after the direction from which they blow.

Planetary winds are also known as permanent winds. This is because they continuously blow in a particular direction throughout the year. Pressure belts control them. The planetary wind is of three types: The trade wind, the westerlies and the polar wind.

 

Seasonal winds: As the name denotes, these winds change their direction subject to change in seasons. They are also called monsoon winds. They blow from sea to land in summer as a result of the low pressure created on the land. And from land to sea during winter.

 

Local winds blow over a small area only during a particular time of a day or for a short period of a year.

 

Beaufort scale, in full Beaufort wind force scale, is a scale devised in 1805 by Commander Francis Beaufort of the British navy for observing and classifying wind force at sea. The Beaufort scale is a scale for measuring wind speed. It is based on observation rather than accurate measurement.

 

An Arab Geographer, called Al-Balakhi, collected climatic data from the Arab travellers and prepared the First climatic Atlas of the world.

Metrologist uses wind vane or weathercock to measure wind direction. To depict the direction and periods (No. of days) of prevailing winds on the map Wind rose diagram is used.

 

Meteorograph or triple register is an instrument that records wind speed and direction, sunshine and precipitation. It also provides graphic representation.

 

 

Brazil has a large area where the average wind speed is low. Gabon, Congo and DR Congo in Africa, Sumatra, Indonesia and Malaysia are the least windy places on the earth.