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Map of pressure systems across North America. A pressure system is a peak or lull in the sea level pressure distribution, a feature of synoptic-scale weather.The surface pressure at sea level varies minimally, with the lowest value measured 87 kilopascals (26 inHg) and the highest recorded 108.57 kilopascals (32.06 inHg).
Map showing atmospheric pressure in mbar or hPa 15-year average mean sea-level pressure for June, July, and August (top) and December, January, and February (bottom). ERA-15 re-analysis. Kollsman-type barometric aircraft altimeter. The mean sea-level pressure (MSLP) is the atmospheric pressure at mean sea level.
Standard sea-level conditions (SSL), [1] also known as sea-level standard (SLS), defines a set of atmospheric conditions for physical calculations.The term "standard sea level" is used to indicate that values of properties are to be taken to be the same as those standard at sea level, and is done to define values for use in general calculations.
Weather maps are created by plotting or tracing the values of relevant quantities such as sea level pressure, temperature, and cloud cover onto a geographical map to help find synoptic scale features such as weather fronts. The first weather maps in the 19th century were drawn well after the fact to help devise a theory on storm systems. [2]
Height above mean sea level (AMSL) is the elevation (on the ground) or altitude (in the air) of an object, relative to a reference datum for mean sea level (MSL). It is also used in aviation, where some heights are recorded and reported with respect to mean sea level (contrast with flight level ), and in the atmospheric sciences , and in land ...
On the top right corner of the model for a surface weather map is the pressure, showing the last two integer digits of the pressure in millibars, or hectopascals, along with the first decimal. For instance, if the pressure at a certain location is 999.7 hPa, the pressure portion of the station model will read 997.
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. Use of constant pressure charts at the 700 and 500 hPa level can indicate tropical cyclone motion.
Weather maps are created by plotting or tracing the values of relevant quantities such as sea level pressure, temperature, and cloud cover onto a geographical map to help find synoptic scale features such as weather fronts. The first weather maps in the 19th century were drawn well after the fact to help devise a theory on storm systems. [3]