Weather stations
by Chris Woodford. Last updated: August 31, 2011.
And the outlook for where you're standing? The sun will shine on your face for the next ten minutes, then a cloud will appear and you'll be completely drenched! Weather forecasters never quite manage to give us the personalized forecast we'd probably like to hear—but that's hardly surprising given how few of them of them there are compared to the rest of us: the weather forecast you get on radio and TV is necessarily a generalization.
The main reason for this is that weather forecasting is a complex scientific and mathematical problem; it leaves even the world's biggest supercomputers scratching their heads! Another reason is that forecasts are compiled using samples of data taken from only a limited number of representative locations—and the closest weather station to where you live may actually be many miles from your house. What do do? One solution to is to try figuring out your own weather forecasts. You'll need a bunch of weather-measuring instruments—a barometer, an anemometer, a thermometer, and a hygrometer— for starters. Or you could buy yourself a weather station: a compact, weather-sampling device that has all these instruments packed in together. Let's find out more about weather stations and how they work!
Photo: Left: Weather forecasting is always helpful—but sometimes it's a matter of life and death. With good forecasting, we can get advance warnings of hurricanes and other extreme weather. This satellite photo shows Hurricane Fran heading for North Carolina and Virginia in August 1989; it went on to cause about $5 billion worth of damage. Photo by courtesy of Great Images in NASA.
What makes weather?
Photo: Right: Clouds play a big part in our weather, blocking out solar radiation and bringing in rain. These are cumulonimbus clouds forming near my home in Dorset, England.
Weather happens because the Sun heats different places on Earth to different temperatures. This makes air rise in some places (creating lows, areas of low pressure, also called depressions) and fall in others (making highs, high-pressure areas, also called anticyclones). Lows and highs make winds blow, and the winds endlessly shuffle different kinds of weather round the planet's surface. Lows bring humid air (soggy with water vapor), which usually means clouds, rain, or snow. Highs signal hot, dry weather in summer and crisp, clear days in winter. Storms happen where lows and highs meet up. All told, weather is pretty complex, but you can get a reasonable idea what it's going to do next if you measure the temperature, pressure, wind speed, and humidity. Bring on the weather station!
What is a weather station?
The key thing about a weather forecast is that it really applies to just one place and, as it's based on a set of measurements, those all have to be made in the same place, at the same time, as well. A weather station is simply a collection of weather-measuring instruments mounted on (or in) the same place. Professional weather stations have very precise instruments stored in a white, sun-proof, louvered box (called a Stevenson screen) and are designed to be read manually. Home weather stations are now typically electronic instruments that are read automatically by a microprocessor (single-chip computer). Either they show their readings on an electronic LCD display or transmit them by wireless (radio) to a computer nearby.
Photo: A traditional weather station inside a Stevenson screen. The white, louvered panels protect the instruments from the direct heat of the Sun but allow air to circulate inside, giving more accurate measurements.
What instruments does a weather station contain?
A typical weather station contains:
- Thermometer: Measures temperature in either degrees Celsius (°C) or Fahrenheit (°F). Home weather stations can often be made to sound an alarm if the temperature rises or falls below a level you set (very handy if you want early warning of a heat wave or frost).
- Barometer: Measures the maximum and minimum air pressure in different units including Pa (Pascals) and mmHg (millimeters of mercury). Most weather stations keep a record of how the pressure has risen or fallen over the last 24 hours or so.
- Precipitation (rainfall) gauge: Measures how much rain (or snow) has fallen. A little plastic beaker with a scale on the side that measures the amount of rain collected in millimeters (or inches) in the last hour, day, week, or month.
- Anemometer: Measures wind speed in kilometers and miles per hour (km/h and mph). Shows both the average wind speed and the gust speed (maximum speed). Usually there is also a vane to measure the wind direction.
- Hygrometer: Measures the humidity (the amount of water vapor in the air, written as a percentage). A humidity of 100 percent means completely saturated air, while 0 percent humidity means totally dry air.
Photo: The main parts of a portable, military weather station. This one can send its readings automatically using a solar-powered transmitter. Photo by Michael Boquette courtesy of US Air Force.
Modern weather stations often have an LCD display that shows all the measurements automatically and updates them instantaneously, saving the need to read the instruments one by one. Using the measurements, a microchip inside will also figure out and display something called the tendency (a rough forecast for the next day's weather, summarized with a simple picture such as a sun (fine day), partly obscured sun (dull day), or raincloud (wet day). Electronic stations also generally have a memory so they can record hundreds of separate measurements covering the last few months. Some stations can be connected to a computer with a USB cable so you can upload your data and draw proper weather and climate charts.
