Mean sea level pressure is calculated based on which factors?

Mean sea level pressure is calculated based on which factors?

• A. Based on current sea level pressure
• B. Based on humidity alone
• C. Based on average air temperature for the past 12 hours and the standard lapse rate of 1.98°C/1000'
• D. Based on wind speed measurements

Answer: (C)

Mean sea level pressure is found by removing the effect of the station’s elevation from the observed surface pressure using the temperature structure of the air above. The calculation relies on how pressure changes with height, which depends on the average temperature of the air in the column. Using the average air temperature over a representative period provides a stable estimate of that temperature, and applying the standard lapse rate gives a consistent vertical temperature gradient to relate the layer’s thickness to height. With those inputs, the hypsometric relationship translates the surface pressure to what it would be at sea level. Humidity or wind speed don’t set this vertical pressure adjustment, and current sea level pressure is not a factor used to compute itself.

Mean sea level pressure is found by removing the effect of the station’s elevation from the observed surface pressure using the temperature structure of the air above. The calculation relies on how pressure changes with height, which depends on the average temperature of the air in the column. Using the average air temperature over a representative period provides a stable estimate of that temperature, and applying the standard lapse rate gives a consistent vertical temperature gradient to relate the layer’s thickness to height. With those inputs, the hypsometric relationship translates the surface pressure to what it would be at sea level. Humidity or wind speed don’t set this vertical pressure adjustment, and current sea level pressure is not a factor used to compute itself.