anti-cyclone. An area of slowly rotating high atmospheric pressure. Cloud formation is restricted and the weather is usually settled.
atmospheric pressure. The weight of the air at a specific location and height.
depression. An rotating area of low atmospheric pressure. The rotation of the depression generates circulating winds.
dew. Water condensed at night from the bottom layer of air.
drizzle. Fine droplets of rain less than 0.5 mm in size.
drought. Long period of dry weather.
climate. The prevailing weather conditions in a particular area.
clouds. Water evaporating from the Earth's surface is held as a vapour in rising warm air. As the air cools the vapour condenses into water droplets which form clouds. Clouds are classified into two main groups: cumulus and stratus (massed and layered). Click here.
cyclone. A depression.
fog. A mass of cool air filled with tiny droplets forming upwards from ground level.
front. A thermal wall across which there is a rapid temperature change. The source of most bad or unsettled weather.
frost. Water that freezes a ground level when the air temperatures falls below 0oC.
hail. Ice particles about 5 mm in diameter formed about dust particles.
high. An anti-cyclone.
isobars. The lines on a weather map that indicate areas of equal air pressure. Tightly packed isobars indicate unsettled weather.
lightning. Discharge of an electric field from a cloud.
low. A depression.
mist. A mass of cool air filled with tiny droplets close to ground level.
precipitation. Water that reaches the ground.
rain. Falling water droplets greater than 0.5 mm in size.
seasons. Climatic changes caused by the position of the earth relative to the sun. The temperate zones have 4 seasons and the tropics two.
shower. A heavy, short lived period of precipitation.
sleet. A mixture of rain and snow.
snow. Ice crystals that 'grow' in clouds.
weather. The daily changes in the atmospheric conditions, primarily the movement of air. In the temperate zones the most influential phenomena are the changes in air pressure. These changes generate the clouds, windand rain that we call the weather.
wind. Wind is the lateral movement of air from high to low pressure areas.
WIND
anabatic. A wind that blows up mountain slopes.
breeze. Winds less than 50km/hr.
cyclone. Area of low pressure often giving rise to violent storms.
foehn wind. Dry, warm air blowing down a mountain.
gale. Winds between 51 and 87 km/hr.
hurricane. Winds in excess of 119 km/hr. A tropical cyclone in the Caribbean and North Atlantic.
jet stream. Strong continuous wind at high altitudes, usually blowing west to east.
katabatic. Gravity induced downward movement of air.
prevailing wind. The predominate wind in a particular area.
roaring forties. Strong westerly winds in the latitudes 40o to 50oS.
squall. Short lived wind in the opposite direction as the prevailing wind.
storm. Winds between 88 and 119km/hr.
tornado. A very strong whirlwind usually less than 500m in diameter, travelling between 20 and 60km/h.
trade winds. Regular winds blowing from sub-tropical to equatorial regions.
typhoon. Tropical cyclone (hurricane) particularly in the China Sea.
whirlwind. A narrow column of rapidly rotating air.
