•   "Cats and dogs eat grass before a rain."

     •   "If the groundhog sees his shadow on February 2, thirty days of winter remain."

The Invention of Weather Station Instruments

A weather station is not a single instrument, but a collection of different pieces of equipment that each measure different aspects of meteorological conditions. Here are some of the attributes measured by a weather station:

Temperature - Temperature is measured using a device called a thermometer. The word thermometer comes from the Greek roots "thermo" (heat) and "metron" (measure). A thermometer measures heat. The first crude thermometers were invented in the 11th century and worked based on heat causing expansion and contraction of the water level in a tube. As the temperature increased, the water expanded and moved higher up the tube. As the temperature decreased, the water contracted and moved farther down.

Pressure - Pressure, or more correctly, atmospheric pressure, is measured using a device called a barometer. The word barometer comes from the Greek roots "baros" (weight) and "metron" (measure). A barometer measures the pressure (weight) associated with the atmosphere. Different types of weather cause the atmospheric pressure to change. Whereas a thermometer works by expansion and contraction of liquid due to a temperature change, a barometer works by monitoring the height of liquid in a tube caused by pressure pushing on the liquid.

Humidity - Humidity is measured using a device called a hygrometer. The word hygrometer comes from the Greek roots "hygros" (wet) and "metron" (measure). A hygrometer measures the amount of water in the air.

Wind - Wind is measured using a couple of different devices. Wind speed is measured using an instrument called an anemometer. The word anemometer comes from the Greek roots "anemos" (wind, or breath) and "metron" (measure). As the wind blows, cups on an anemometer cause it to turn like a windmill. The speed of rotation is measured using electronics built inside. Wind direction is measured using a device called a weather vane. The vane on the weather vane causes it to point in a direction. The direction is measured by electronics monitoring the vane shaft.

The old adage "The sum is greater than its parts" is applicable to weather instruments.  Each piece of equipment mentioned above measures some attribute of weather, but when combined, they allow meteorologists to calculate and extract some other useful measurements, including

     •   Dew Point: the point where vapor forms dew, rain, or snow

     •   Frost Point: the point where vapor forms frost

     •   Wind Chill: the apparent temperature one feels on the skin

Weather Instruments Now

You have probably seen on the news, or perhaps even witnessed firsthand, severe weather in the form of hurricanes, blizzards, or tornadoes. These types of weather can be very dangerous. Weather instruments today combine many different technologies to try to predict dangerous weather in order to provide people with early warnings so they can take cover or evacuate.

Weather Satellites - Weather satellites, orbiting the earth, use specialized imaging systems to look at conditions in the earth's atmosphere. Using sensors that create images in the visible range, these satellites provide maps that show cloud cover, cloud movement, and weather fronts. Using infrared sensors, they provide maps that uncover hidden weather features like land and ocean temperatures, the "eyes" of hurricanes, and ocean current patterns.

Doppler Radar - Doppler radar systems were first developed just after the Second World War. Radar operators noticed that weather conditions, such as rain, sleet, and snow, caused "noise" to appear in the radar signal. After the war, when the radar operators returned to civilian careers, some continued their work to help with weather measurements.