Improving Stable Boundary-Layer Height Estimation Using a Stability-Dependent Critical Bulk Richardson Number

H. Richardson, S. Basu, A.A.M. Holtslag

Research output: Contribution to journalArticleAcademicpeer-review

19 Citations (Scopus)


For many decades, attempts have been made to find the universal value of the critical bulk Richardson number (Ri Bc ; defined over the entire stable boundary layer). By analyzing an extensive large-eddy simulation database and various published wind-tunnel data, we show that Ri Bc is not a constant, rather it strongly depends on bulk atmospheric stability. A (qualitatively) similar dependency, based on the well-known resistance laws, was reported by Melgarejo and Deardorff (J Atmos Sci 31:1324–1333, 1974) about forty years ago. To the best of our knowledge, this result has largely been ignored. Based on data analysis, we find that the stability-dependent Ri Bc estimates boundary-layer height more accurately than the conventional constant Ri Bc approach. Furthermore, our results indicate that the common practice of setting Ri Bc as a constant in numerical modelling studies implicitly constrains the bulk stability of the simulated boundary layer. The proposed stability-dependent Ri Bc does not suffer from such an inappropriate constraint.
Original languageEnglish
Pages (from-to)93-109
JournalBoundary-Layer Meteorology
Issue number1
Publication statusPublished - 2013



  • large-eddy simulation
  • turbulence structure
  • resistance laws
  • climate model
  • surface
  • depth
  • formulations
  • evolution
  • profile
  • range

Cite this