Meteorology, mee tee uh ROL uh jee, is the study of the earth's atmosphere and the variations in atmospheric conditions that produce weather. Meteorologists measure precipitation and such conditions as wind, temperature, and humidity. They also collect and measure gases, such as ozone and carbon dioxide, that occur in the atmosphere. Meteorologists use the data they gather to study and predict weather and climate. The word meteorology comes from Meteorologica, the title of a book by the ancient Greek philosopher Aristotle. In this book, Aristotle included his explanations of various weather conditions.