Customize Your Weather. Privacy Policy. Pressure Unit Convertor Weather. Current Hazards. Current Conditions. Surface Observations Satellite Observed Precipitation. Rivers and Lakes. Mean Sea Level Pressure is the pressure reading most commonly used by meteorologists to track weather systems at the surface.
It is a "reduced" pressure, which uses observed conditions rather than "standard" conditions to remove the effects of elevation from pressure readings. This reduction estimates the pressure that would exist at sea level at a point directly below the station using a temperature profile based on temperatures that actually exist at the station.
In practice the temperature used in the reduction is a mean temperature for the preceding twelve hours. Mean sea level pressure should be used with caution at high elevations as temperatures can have a very profound effect on the reduced pressures, sometimes giving rise to fictitious pressure patterns and anomalous mean sea level pressure values. Altimeter Setting is the pressure reading most commonly heard in radio and television broadcasts.
It is not the true barometric pressure at a station. Instead it is the pressure "reduced" to mean sea level using the temperature profile of the "standard" atmosphere, which is representative of average conditions over selected area. The altimeter setting is the pressure value to which an aircraft altimeter scale is set so that it will indicate the altitude above mean sea level of the aircraft on the ground at the location for which the pressure value was determined.
The altimeter setting is an attempt to remove elevation effects from pressure readings using "standard" conditions. Low pressure versus high pressure: A low pressure system, or "low," is an area, where the atmospheric pressure is lower than that of the area surrounding it.
Conversely, a high pressure system, or "high," is an area, where the atmospheric pressure is greater than that of the surrounding area. Saying that the pressure is high or low is relative to the characteristics of the air surrounding the air mass. If you say that the pressure is high when it's above average and low when it's below average is an inadequate definition.
High and low pressure could be defined by saying that, on average, the air in the Troposphere is generally rising in a low pressure system and sinking in a high pressure system. The hyperlink to [Conversion to sea-level pressure] Conversion to sea-level pressure Calculator. Related Calculator. Temperature and pressure at destination Conversion to sea-level pressure Atmospheric pressure from altitude Altitude from atmospheric pressure Prospect distance from the ground Distance between two places on the earth Distance and azimuth between two cities.
Sea-level pressure P 0. Derivation of an equation.
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