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Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
Comparison of a graph of International Standard Atmosphere temperature and pressure and approximate altitudes of various objects and successful stratospheric jumps The International Standard Atmosphere ( ISA ) is a static atmospheric model of how the pressure , temperature , density , and viscosity of the Earth's atmosphere change over a wide ...
Such maps have been in use since the mid-19th century and are used for research and weather forecasting purposes. Maps using isotherms show temperature gradients, [2] which can help locate weather fronts. Isotach maps, analyzing lines of equal wind speed, [3] on a constant pressure surface of 300 or 250 hPa show where the jet stream is located.
Simultaneous barometric readings from across a network of weather stations allow maps of air pressure to be produced, which were the first form of the modern weather map when created in the 19th century. Isobars, lines of equal pressure, when drawn on such a map, give a contour map showing areas of high and low pressure. [33]
The stations measure wind speed, direction, and gust; barometric pressure; and air temperature. In addition, all buoy and some C-MAN stations measure sea surface temperature, and wave height and period. [44] Conductivity and water current are measured at selected stations. All stations report on an hourly basis.
The Danish Meteorological Institute report record barometric pressure for Denmark (since 1874) as: Highest air pressure: 23 January 1907, Skagen and Copenhagen 1062.2 hPa. [106] [107] Lowest air pressure: 20 February 1907, Skagen 943.5 hPa. [106] Danish records both occurred within a month during the same winter, and same winter as Norwegian ...
There is some evidence that thunderstorms and barometric pressure can trigger headaches, but it’s unclear if “regular” air pollution — such as bad air from wildfires — is a migraine ...
Barometer – an instrument used to measure atmospheric pressure using either water, air, or mercury; useful for forecasting short term changes in the weather; NOAA continental US weather forecast map for November 7, 2006. Ceiling balloon – a balloon, with a known ascent rate, used to measure the height of the base of clouds during daylight