In the Standard Atmosphere a pressure of 500 mb occurs at an altitude of 5574 m (18,289 ft.). The altitude of the 500-mb level over San Diego at the time of this sounding was that of the Standard Atmosphere. This relatively warm atmospheric column reflected the conditions that generally exist throughout the troposphere during late summer in middle and high latitudes, and especially 2015 in the Southwest."a. higher thanb. the same asc. lower than