Return to the Climate Glossary Index  Climate Glossary

Mean Sea Level (MSL)

MSL stands for Mean Sea Level. It is necessary to convert the pressure readings to equivalent mean sea level pressures, otherwise the important horizontal changes in pressure would be overwhelmed by vertical variations simply due to differences in height between observing stations. In this way, a Mean Sea Level Pressure map will then show pressures affected by changing weather conditions, not because of changing altitude.