Kristen's Classroom: Weather instruments

AUSTIN (KXAN) — Meteorologists use many different instruments to observe and forecast the weather. Some sit at the surface... others remain far above the ground, all are important in knowing and predicting weather patterns.

Automated Surface Observing Systems (ASOS)

A joint effort between the National Weather Service, the Federal Aviation Administration, and the Department of Defense (DOD), the Automated Surface Observing System program consists of close to a thousand observation sites running non-stop, updating every minute, 24 hours a day, every day of the year. The ASOS sites report:

• Sky conditions: cloud height and amount (clear, scattered, broken, overcast) up to 12,000 feet
• Visibility (to at least 10 statute miles)
• Current weather conditions: type and intensity for rain, snow, and freezing rain.
• Obstructions to vision: fog, haze
• Pressure: sea-level pressure, altimeter setting
• Temperature
• Dew Point (moisture)
• Wind: direction, speed and character (gusts, squalls)
• Precipitation accumulation

Weather balloons

How do we know what the weather is above our heads? Weather balloons. These balloons launch twice a day from nearly 900 stations worldwide (92 in the U.S.), every day, carrying a Styrofoam box of instruments known as radiosondes.

Radiosonde sensors measure upper-air conditions such as atmospheric pressure, temperature and humidity, wind speed and direction, relaying back data to a ground receiver by way of a radio frequency transmitter.

These sensors are tied to a string (along with a parachute) to the balloon. As the balloon ascends and the pressure eventually causes the balloon to pop, the parachute attached to the string inflates and the sensor returns to the surface.

These balloons rise at about 1,000 feet per minute, for a flight time up to 2 hours, ascending to over 100,000 feet and can drift more than 125 miles from where it was originally launched.

Weather satellites

The United States has an entire fleet of weather satellites— over a dozen!

The two polar orbiting satellites observe the same spot on the Earth twice daily, once during the day and once at night. Polar orbiting satellites provide imagery and atmospheric soundings of temperature and moisture data over the entire Earth.

Geostationary satellites are in orbit 22,000 miles above the equator, spin at the same rate as the Earth, and hover over the same area. This allows satellites to take a picture of the Earth, at the same location, every 30 minutes... or in the case of severe weather, every 30 seconds.

Other instruments

In addition to the tools listed above, meteorologists also use ocean buoys and aircraft data to help support forecasts and computer models.