The atmospheric pressure at mean sea level either directly measured by stations at sea level or empirically determined from the station pressure and temperature by stations not at sea level Used as a common reference for analyses of surface pressure patterns
The sea level pressure is a correction of the station pressure to sea level This correction takes into account the standard variation of pressure with height and the influence of temperature variations with height on the pressure The temperature used in the sea level correction is a twelve hour mean, eliminating diurnal effects Once calculated, horizontal variations of sea level pressure may be compared for location of high and low pressure areas and fronts
Atmospheric pressure extrapolated to sea level Primarily useful for fire weather in determining the location of cold and warm fronts, wind directions, and relative wind speed
The atmospheric pressure at mean sea level, either directly measured or most commonly mathematically determined from the observed station pressure Sea level pressure is calculated so that a surface pressure chart won't show giant areas of low pressure over all of the mountain ranges
The atmospheric pressure at mean sea level, usually determined from the observed station pressure