Sunday, 15 March 2015

Wind

Wind is the movement of air
Wind occurs when air moves from an area of high pressure to an area of low pressure
Pressure gradient is the difference in air pressure between two locations. The greater the pressure gradient, the faster the wind speed
Wind is measured by its speed, direction and frequency
Wind speed is the rate of movement of air measured in km/h(kilometer per hour) using an anemometer 
Wind direction is the direction from which the wind blow measured using a wind vane. The wind vane points to the direction from which the wind is blowing 
Wind frequency is the percentage of time where a wind blows from one particular direction. The direction where the wind blows the most frequent is known as the prevailing wind.
Wind direction and frequency is recorded in a wind rose.

Sea Breeze
In the day, the land is warmer than the sea, since the land conducts heat faster than the sea. This results in a low pressure at the land and high pressure at the sea


Land Breeze
At night, the sea is warmer than the land, since the sea loses heat slower than the land. This results in a lower pressure at the sea and a higher pressure at the land

Monsoon Winds
Monsoon winds are regional wind patterns that reverse direction seasonally. There is the southwest monsoon and the northeast monsoon

Southwest monsoon*
Take place from June to September.

Northeast Monsoon*
Take place from October to February

*This is the name of the winds only at the Northern hemisphere!

The monsoon wind doesn't blow in a straight direction due to the Coriolis effect. The Coriolis effect is a force produced by the rotation of the earth. This force change the direction of winds. Therefore, monsoon winds doesn't blow in a straight direction and will change i's direction when it crosses the equator.

Saturday, 14 March 2015

Air Pressure

Air pressure is the force exerted on a unit area of the Earth's surface by the mass of air above it.
Air pressure is measured using a barometer, measured in millibars (mb).
Air pressure is considered high if it is more than 1013 mb and considered low if it is less than 1013 mb
The measurement of air pressure can be used to produce a weather map or a synoptic chart.
Factors Affecting Air Pressure
Altitude
The higher the altitude, the lower the air pressure
At a higher altitude, there is a smaller mass of air above compared to the mass of air at a lower altitude. Therefore, the air is less dense so the air pressure is lower