Dewpoint formula

From Glossary of Meteorology



dewpoint formula

A formula for the calculation of the approximate height of the lifting condensation level.

Therefore, it is employed to estimate the height of the base of convective clouds, under suitable atmospheric and topographic conditions. In a practical but simplified form, it may be stated
ams2001glos-De22
where H is the height above the surface in km and T and Td are the temperature and dewpoint in degrees Celsius. This is derived from assuming that the temperature decreases 9.8°C and the dewpoint decreases 1.8°C for each km increase in altitude, values which are approximately correct for a well-mixed boundary layer. The convective-cloud height diagram is a graphic form of this relationship.


Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.