The instrument typically used to measure atmospheric pressure is called a barometer. Barometers come in various types, including mercury barometers and aneroid barometers. A mercury barometer measures pressure based on the height of mercury in a glass tube, while an aneroid barometer utilizes a sealed metal chamber that expands or contracts with changes in pressure. Barometers are vital in meteorology, helping predict weather changes by measuring pressure fluctuations. A decrease in atmospheric pressure often indicates approaching storms, while an increase can suggest fair weather. Understanding atmospheric pressure is essential for weather forecasting and various scientific studies.