GUST, a General Unified Similarity Theory for the calculation of turbulent fluxes in numerical weather prediction models for unstable conditions

Details

• Alternative Title:
  A General Unified Similarity Theory for the calculation of turbulent fluxes in numerical weather prediction models for unstable conditions
• Personal Author:
  Long, Paul E.
• Corporate Authors:
  National Meteorological Center (U.S.)
• NOAA Program & Office:
  NWS (National Weather Service) ; NCEP (National Centers for Environmental Prediction)
• Description:
  Flux-profile relations are presented for wind and temperature in the surface layer of the unstable atmospheric boundary layer. The flux-profile relation for wind is derived from the so-called 'KEYPS' equation, a quartic equation whose real, positive root is equal to the nondimensional wind shear. The analogous relation for potential temperature is a new cubic equation whose real, positive root is equal to the nondimensional temperature gradient (Helfand, 1984). It is assumed that the nondimensional humidity gradient is equal to that for temperature. The nondimensional gradients reduce to conventional empirical relations for conditions of weak instability but, unlike the conventional relations, go to the 'free-convection' limit for conditions of strong instability. The integrated forms of the flux-profile relations yield expressions which can be solved iteratively for the Obukhov length which, in turn, can be used to compute surface momentum, heat, and moisture fluxes. Although the flux-profile relations and their-integrated forms have no evident closed-form solutions, rational fraction and asymptotic approximations are derived that are no more costly computationally than the expressions currently in use in numerical prediction models that use conventional flux-profile relations.
• Content Notes:
  Paul E. Long, Jr. ; "January 1984." ; "This is an unreviewed manuscript, primarily intended for informal exchange of information among NMC staff members." ; System requirements: Adobe Acrobat Reader. ; Includes bibliographical references.
• Series:
  Office note (National Centers for Environmental Prediction (U.S.)) ; 302
• Document Type:
  Office Note
• Place as Subject:
  United States
• Rights Information:
  Public Domain
• Compliance:
  Library
• Download URL:
  https://repository.library.noaa.gov/view/noaa/11507/noaa_11507_DS1.pdf
• File Type:
  [PDF - 1.26 MB]
• Collection(s):
  National Weather Service (NWS)
• Main Document Checksum:
  urn:sha256:d168d9a169399f2dc7db49661413887419c8c0f757307cbc646cf69d13d27acd