Introduction

How much preparation is necessary before the MetLink project begins? What should you bear in mind when setting up a weather station at school or home? This page addresses these questions.

For making weather measurements, you do not need expensive equipment. Indeed, you can make perfectly adequate measurements with home-made equipment. To find out how to make a rain gauge, click on RainCatch. To find out how to make a range of other meteorological instruments, click on Simple weather measurements at school or at home.

However simple your weather instruments, you can take part in the MetLinkInternational project. The only instrument you must have is a thermometer – to measure current temperature. Only two measurements are compulsory: current temperature and wind force. Without them, the database will not accept your observation.

Exposure of instruments

Thermometers, rain gauges and other instruments should not be located close to buildings, though for security reasons they may have to be.

You are endeavouring to measure air temperature. Therefore, you must make sure the sun does not shine on your thermometer. If you possibly can, you should place it in a louvred screen, i.e. a screen which has slats to allow the air to circulate around the thermometer. Do not place a thermometer too near a building, because walls retain heat. The walls can heat up the air nearby so that it is warmer than the air circulating over an open area such as a school playing field.

If you are using a minimum thermometer, you must make sure it is not exposed to the sky at night. If it is, it will lose heat to space and thus give a temperature reading that is too low – maybe several degrees too low on a clear night. To measure the minimum air temperature, you need to shade the thermometer whilst still allowing air to circulate around it. Ideally, both maximum and minimum thermometers should be placed inside a louvred screen.

Do not place your rain gauge too near a wall, tree, hedge or fence.

Wind gets funnelled between buildings and hedges and deflected when it flows around and over buildings and other obstacles. What you enter in the MetLink database should be the wind direction that is representative of your wider local area.

To gauge wind direction, you need some sort of indicator. This may be, for example, a home-made wind sock (to view one, click on home-made wind vane) or a flag or pointer on top of a pole or building (to view a home-made pointer, click on wind vane). You can also use soap bubbles to indicate wind direction. Ignore the movements of clouds; wind direction normally changes with height.

Timing of observations

You should try to make your weather observations at the same time each day. You need to decide in advance what time suits you best and then stick to it as closely as you can from day to day. You need to enter in the MetLink database the date and time each observation was actually made. To do this, you use the drop-downs on the date and time section of the project’s data-entry page.

Wind force

You do not need equipment for measuring the strength of the wind. You can estimate the strength by means of the Beaufort Scale. All you need to do is observe the effects of the wind on leaves, dust, smoke, flags, etc. For an explanation, click on Beaufort Wind Scale for Land Areas.

If you have a device for measuring wind speed (called an anemometer), you can use the Beaufort Scale to convert speed to force.

Barometric pressure

Make sure you have set your barometer before the project begins. To find out how to do this, click on How to set your barometer.

Cloud amount and type

For assistance over cloud recognition, click on Cloud identification, Clouds or The nature of clouds. If you would like to buy a cloud identification chart, which is a laminated card for use in the field, click on Buy a cloudchart from the Royal Meteorological Society's online shop.

Automatic weather stations and electronic instruments

Care is needed when using automatic weather stations or electronic instruments (particularly electronic thermometers). Readings need to be checked. This is very important, as these weather stations and electronic instruments can give readings that are significantly in error. For guidance and advice on the use of automatic weather stations and electronic instruments, click here.

Understanding satellite images

Images from meteorological satellites can tell you a great deal about the weather. The so-called ‘visible images’ show you what you would see if you were in the satellite yourself looking in black and white. Infra-red images provide information about the temperatures of clouds and the earth’s surface. Water-vapour images show distributions of moisture in the atmosphere.

For an introduction to images from meteorological satellites, click on An introduction to satellite pictures. Please follow the links on this page to find out how to obtain high-quality images from the Dundee Satellite Receiving Station (free of charge) and guidance on how to interpret pictures from meteorological satellites. Please click, too, on the link called More on this story.

Understanding weather charts

For an introduction to weather charts, click on Interpreting weather maps. Then click on Anticyclones, depressions and fronts and follow all the links.

In the northern hemisphere, winds blow anticlockwise around depressions.
In the southern hemisphere, they blow clockwise around depressions.
For an explanation of weather charts in the southern hemisphere, click on The weather map.

For an introduction to the near-equatorial belt of cloud and rain known as the Intertropical Convergence Zone (ITCZ), click on What is the Intertropical Convergence Zone?. This includes an introduction to the tropical weather systems that develop from the ITCZ. For an introduction to the structure of the ITCZ, click on Cloud clusters of the ITCZ.

For an introduction to the vigorous tropical storms known as cyclones or hurricanes, click on Hurricanes. For detailed information about hurricanes, click on National Hurricane Center. For the answers to questions which are frequently asked about hurricanes, click on Frequently asked questions. For information about the names and naming of hurricanes in different parts of the world, click on Tropical Cyclone Names.

The weather symbols used by meteorologists

On weather charts, meteorologists use symbols to describe clouds and the weather. For details of the symbols and information about how they are used, click on Weather symbols and on Plotted weather charts.

To see the symbols used for plotting wind speed, click on Wind speed.

Converting meteorological units

To convert a Fahrenheit temperature reading to Celsius: first deduct 32 and then multiply the value you get by 5/9.
Thus: 59°F = (59-32)x5/9 = 27x5/9 = 15°C.
To convert a Celsius temperature reading to Fahrenheit: first multiply by 9/5 and then add 32.
Thus: 20°C = (20x9/5)+32 = 36+32 = 68°F.

To convert inches to millimetres and vice versa:
1 inch = 25.4 mm and 1 mm = 0.03937 inch.

To convert barometric pressure units:
millibars = inches times 33.8639, so 30 inches = 1015.9 mb and 1000 mb = 29.53 inches;
millibars = millimetres times 1.3332, so 760 mm = 1013.23 mb and 1000 mb = 750.1 mm.

To convert wind-speed units:
[kt = knot; m/s = metres per second; kph = kilometres per hour; mph = miles per hour]
1 kt = 0.515 m/s and 1 m/s = 1.94 kt;
1 kt = 1.853 kph, so 1 kph = 0.54 kt;
1 kt = 1.152 mph, so 1 mph = 0.87 kt.

Online guidance on weather observing

For an introduction, click on Weather observations.