From AMS Glossary
An equation relating the thickness, h, between two isobaric surfaces to the mean virtual temperature of the layer: pressure levels p1 and p2, respectively; Rd is the gas constant for dry air; is the mean virtual temperature of the layer; and g is gravity.
Wallace, J. M., and P. V. Hobbs, 1977: Atmospheric Science: An Introductory Survey. Academic Press, 55–57.
term edited 9 December 2015