Introduction to weather and climate

Today's objectives were as follows:

- To be able to define the terms weather and climate.
- To know the names of the key components of weather.
- To know the names of the key weather instruments.

Weather is the short term state of the atmosphere over a small area. By contrast, climate is the 'average weather', usually taken over a period of 30 years, for a larger area. It considers long term trends.

You need to be able to define the following aspects of the weather, know how they are measured, and give the units of measurement:

- precipitation
- temperature
- air pressure
- cloud cover
- wind speed
- wind direction
- visibility

Precipitation means water falling from the sky in any form eg. rain, sleet, snow, hail. It is measured in millimetres using a rain gauge.

Temperature means how hot or cold it is. It is measured in degrees, using a thermometer.

Air pressure is how 'heavy' the air is. It is measured in millibars using a barometer.

Cloud cover is how much of the sky is hidden by clouds. You use your eyes to measure cloud cover. Cloud cover is expressedin oktas - one okta cover means that one eighth of the sky is obscured by clouds.

Wind speed is how fast the wind is blowing, and it is measured using an anemometer. As you will know from our fieldwork in the lesson, it can be given in a variety of units eg. miles per hour, kilometres per hour, metres per second, knots.

Wind direction is which direction the wind is coming from - it is measured using a weather vane and given as a compass direction eg. north, south, east, west.

Visibility means how far you can see. It is measured using a lightmeter, and usually given in metres.