Tag: elements of weather and climate :rainfall and air pressure

• Among the two main agents of erosion in India, wind erosion contributes to erosion in close to 10% area in India. Approximately 90% area is eroded by water.
• Hence option A is correct.

Coromandal coast receives winter rainfall because of the retreating monsoon and the North-east Monsoon winds which pass over the Bay of Bengal. There they get moisture and when they reach the Tamil Nadu coasts they cause rainfall there. During the winter season, the northeast trade winds prevail over the country.

The subtropical high pressure belt is often called horse latitude. It is situated around $30^o$ Northern and Southern hemisphere.

The monsoon is a seasonal modification of the general planetary wind system. Monsoon winds are most powerful India and China. During summer, the interior of Asia become hot and low pressure develops there. On the other hand, the water surface of Indian ocean remains cooler and the pressure gradient is towards the heated interior. So monsoon wind blows from water to land, it is moist and brings lots of rain. In winter the water is warmer than the land surface. As a result, the wind blows from the interior towards the ocean so it is cold and dry. 

Wind rose is a tool which gives us the idea of how typically the speed and direction of the wind are distributed at a particular location. It consist of 8 compass points. 

Wind Rose is the instrument to measure wind speed and direction of the wind. They help to identify the direction and frequency of wind in a particular place. One of the important use of Wind Rose in the construction of airport runways, so that the airplane can take the best takeoff and landing point towards and away from the wind.

The winds which change their direction periodically with the change in season are known as periodic winds. They blow at regular intervals. They blow during particular time of the day or year. Localized differences in pressure and temperature are the main cause of periodic winds. For example, land and sea breezes and the seasonal wands.

A wind rose diagram summarizes information about wind at a particular location over a specific period of time. It gives the percentage of time for which the wind blows from each direction, the strengths of these winds and the percentage of time calm air or light winds are observed. 

Wind is the horizontal movement of the air. The differences in air pressure within our atmosphere causes the wind. Under high pressure, air moves towards area of low pressure. The greater the difference in pressure, the faster the air flows. Wind is described with direction and speed. The direction from which the wind is blowing describes the direction of wind.

• The horizontal movement of air is called wind, hence option B is correct.
• Air current involves both horizontal and vertical movement of air thus incorrect.
• Cyclone is a circular movement of air.
• Tides are the rise and fall of the sea level due to gravitational pull of moon and sun.