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What Different Instruments Do Weather Forecasters Use to Make Predictions?

Humans have tried to predict the weather for centuries, but it wasn't until the advent of modern technology that forecasting became a more reliable science. Today, weather forecasters employ a variety of tools to gather data, then analyze the data or use it in mathematical, computer-calculated models of weather patterns. Some of these instruments are fairly old, while others are of more recent provenance.

Barometer
- A barometer is a device that measures air pressure. Dense, cold air sinks beneath warm air, which is less dense and rises, so pressure measurements help track the movement of warm and cold fronts and predict changes in weather. Low pressure often precedes foul weather. Traditionally, barometers used a column of mercury that would rise or fall inside a glass tube in response to changes in air pressure; modern barometers, however, use a flexible metal box called an anaeroid cell to turn a needle on a meter.
Anemometers and Wind Vanes
- A wind vane points the same way as the wind and thus indicates wind direction, while an anemometer measures wind speed. Wind turns metal cups or vanes so that the anemometer spins in the wind; by recording the number of rotations the device can determine how fast the wind is blowing.
Psychrometers
- A psychrometer is a device that measures relative humidity, the amount of water vapor in the air. Psychrometers typically use two thermometers, one of them covered in a wet cloth. As the water in the cloth evaporates, it takes up heat, decreasing the temperature on the wet bulb thermometer. The difference in temperature recorded by the two thermometers is a reflection of the humidity level.
Thermometer
- A thermometer is one of the simplest and most familiar weather devices; it measures the air temperature using a liquid whose volume increases or decreases with the change in temperature. Mercury and alcohol are common liquids for thermometers. Some more modern thermometers use a bimetal gauge instead; since the two metals in the bimetallic strip each expand to a different extent as the temperature increases, the bimetallic strip will bend with increasing temperature.
Weather Satellites
- Weather satellites are among the newest weather forecasting instruments. Stationed high above the Earth, they take pictures of cloud formations, snow cover and ocean current patterns; they are invaluable tools in today's weather forecasting. Using weather satellites, meteorologists observe hurricane formation in the South Atlantic, for example, and have advance warning long before the hurricane makes landfall.

Nature