C is for …

Climate
The climate of an area is a summing up of the day to day values of weather elements over a period of time, and how they affect the locality.

The main climatic elements are:

• precipitation,
• temperature,
• sunshine,
• humidity
• wind speed.

Climate can be described in terms of average and extreme values as well as frequency of occurrence.

The Gobi Desert

Records normally have to be kept for a minimum of 30 years in order to build up a representative picture of the climate of an area.
The main factors governing climate are: latitude, altitude, global geographical position and local geographical features.

Clouds

Clouds are a collection of tiny water droplets, ice crystals or a mixture of both, suspended in the atmosphere.

They are named depending on how they are formed, their shape, composition and height. Three main types are stratus, cumulus and cirrus.

Stratus comes from the latin for "layer" and is generally flat-looking, low, grey and continuous cloud. Status-type cloud usually brings drizzly rain. Low stratus can persist around our coasts when there is mild, southwesterly wind.

Cumulus cloud

Cumulus, from the latin for "heap" or "pile", is the classic white fluffy cloud, at medium levels, often interspersed with blue sky.

Cumulus-type clouds bring showers with bright spells in between.
Cirrus means "tuft" or "filament" and this type often appears as streaks of white, fibrous cloud at high levels.

Cirrus cloud

Cirrus cloud does not give rise to any precipitation, but can be an indicator of weather systems on the way.

There are many other cloud types which are a variation, or combination, of these basic types.

For instance Cumulonimbus (nimbus meaning "rain-bearing") are huge dark cumuliform clouds, sometimes with an anvil-shaped head, which can bring thunder and hail.

Cold Front

Cold front may lead to precipitation

You will often see forecasters refer to wavy lines with blue triangles drawn onto weather maps. This is how cold fronts are denoted.

A front is an area of transition between two different airmasses (see A-section) where gradients of temperature and humidity change rapidly over a small horizontal area. Along a cold front, colder air is undercutting and replacing warmer air.

At the earth’s surface this can be marked by a rise in pressure and a fall in temperature and humidity, along with a veer, clockwise, in wind direction. As a cold front passes it will often be accompanied by an outbreak of rain, and followed up by showers.