Meteorology is the study of the atmosphere and weather phenomena. Aristotle wrote one of the earliest works on meteorology in 340 BC called "Meteorologica" which described the science of the earth's geology, elements, hydrology, winds, and weather. Key early weather instruments included the water thermometer in the 1500s, the mercury barometer invented in 1643 to measure atmospheric pressure, and the anemometer created in 1667 to measure wind speed. These inventions helped advance understanding of the atmosphere and forecasting of weather events like hurricanes and thunderstorms.