Sea level pressure is defined as:

Sea level pressure is an important meteorological concept and is defined as the barometric pressure that has been adjusted to reflect the pressure at sea level, assuming a standard atmosphere. This adjustment is necessary because atmospheric pressure decreases with altitude, meaning that measurements taken at different elevations would not accurately represent the pressure at sea level. By mathematically reducing the pressure readings from various altitudes to sea level conditions, meteorologists can compare pressures from different locations on a common ground.

The process involves using the actual pressure observed at a station and correcting it for the height of that location above sea level. This makes sea level pressure a crucial reference point in weather forecasting and analysis, allowing for accurate comparisons and assessments of atmospheric conditions across different geographical areas.