ilmapaineen

Ilmapaineen, in Finnish meteorology, refers to atmospheric pressure—the force per unit area exerted by the weight of the Earth's atmosphere on surfaces at a given location. It results from gravity acting on the air column above and varies with altitude, temperature, and weather systems.

At sea level, the standard atmospheric pressure is about 1013.25 hPa (hectopascals), equivalent to 101,325 Pa. In meteorology the historical unit millibar (mb) is still encountered, with 1 hPa equal to 1 mb. Pressure values can range widely across the globe, typically from roughly 870 hPa to 1080 hPa in extreme weather conditions. Readings are often adjusted to sea level for comparison between locations.

Pressure is measured with barometers, including mercurial, aneroid, and digital devices. Modern practice often uses digital sensors that feed data into weather models. Pressure fields are depicted on weather maps as isobars, lines connecting points of equal pressure, which help identify high and low pressure systems and general weather patterns.

Weather and climate are strongly influenced by ilmapaineen variations. High-pressure systems (anticyclones) are generally associated with sinking air and clearer skies, while low-pressure systems (cyclones) involve rising air and cloudier, wetter conditions. Pressure tends to fall in advance of storms and rise after their passage. Variations in atmospheric pressure also have practical implications for aviation, navigation, and altimetry.

Historically, measurements of atmospheric pressure began with early barometers developed in the 17th century, with standardization and global data networks expanding in the 19th and 20th centuries, forming a cornerstone of modern meteorology.