Lesson 1. An Introduction to Atmospheric Variables

This is a sample lesson page from the course METEO 101 which is part of the online Certificate of Achievement in Weather Forecasting offered by the Penn State Department of Meteorology. Any questions about this program can be directed to: David Babb


Young child standing next to an instrument shelter.
A cooperative weather station at Granger, Utah (circa 1930).Courtesy NOAA Photo Library

Like many scientists, meteorologists rely on an army of technical assistants to take observations in their "open-air laboratory" (a.k.a., the atmosphere). Approximately 11,000 "cooperative observers" volunteer to observe daily precipitation and maximum and minimum temperature in their hometowns. These ordinary citizens (many of whom are weather enthusiasts) provide crucial data that supplement the National Weather Service's primary network of observations (taken at approximately 1500 airports across the nation).

At these "primary" airports however, trained government observers or automated weather instruments are responsible to collecting routine weather observations.  The set of routinely collected measurements includes temperature, moisture, air pressure, wind direction, wind speed, cloud cover, visibility, precipitation and several other atmospheric variables.

This lesson will immerse you in the culture of weather observation.  You will learn about some of the key weather variables and why forecasters are interested in these parameters.  You will also learn about how all of these observations can be easily displayed on weather maps.   This knowledge will allow you to take your first step toward your goal of becoming a competent apprentice forecaster.  By gaining insight on the atmosphere's present state, you will be better prepared to fashion your own weather forecast or, at the very least, give more context to the weather forecasts you see and hear on television and radio.