Sea level height measures the height of the sea. Sea level height is measured (in meters) above or below a reference height. In this case, sea level height is measured relative to the mean, or average, sea level height. Positive values mean that the sea level height is higher than average by a number of meters. Negative values mean that the sea level height is lower than average by a number of meters.
This parameter is a 5-day average of sea level height.
The height of the surface of the ocean will change for many reasons. For instance, daily tides can substantially change the sea level height. Ocean circulation, or currents, will also change the sea level height. When the parameter is averaged over 5 days, it’s not as sensitive to tides or other short-term influences.