Communications – introduction

Introduction. Communication plays a very important part in modern society. We have advanced from the days of the old land-line based telephone and postal (snail) mail to mobile phones and e-mail. Technology has given us the ability to communicate with each other instantly and anywhere in the world. It has…

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Air masses and fronts

Air masses are large areas of air having the same characteristics throughout. They may be either warm or cold, depending on whether their source is polar or tropical. They are also classified as either maritime or continental. When two different air masses meet they form a boundary which is known…

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Atmospheric pressure, depressions and anti-cyclones

Atmospheric pressure and temperature are mainly responsible for our weather systems. Atmospheric pressure is the pressure that the air exerts on the surface of the earth and everything on it. It changes with altitude and temperature. The air pressure in Johannesburg is less than that at the coast. When the…

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Wind

Vertical and horizontal movement. Wind can be defined as the movement of air from a high pressure to a low pressure area. Consider two columns of air AB and CD. They are of equal cross sectional area, height and temperature and the pressure at A and C are equal and…

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Rain, snow and hail

If the cooling process which gives rise to cloud formation is continued, the droplets of which the cloud consists grow in size until they become too heavy to remain suspended in the air and they fall to the ground as rain. The longer the droplets are held aloft by the…

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Fog and mist

The formation of fog and mist is basically the same as that of clouds. In cloud the resulting condensation into visible particles takes place high above the ground, but for fog or mist, the condensation takes place on the surface of the sea or ground. The only difference between fog…

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