A Climatology of Nocturnal Low-Level Jets at Cabauw

P. Baas, F.C. Bosveld, H.K. Baltink, A.A.M. Holtslag

Research output: Contribution to journalArticleAcademicpeer-review

109 Citations (Scopus)

Abstract

A climatology of nocturnal low-level jets (LLJs) is presented for the topographically flat measurement site at Cabauw, the Netherlands. LLJ characteristics are derived from a 7-yr half-hourly database of wind speed profiles, obtained from the 200-m mast and a wind profiler. Many LLJs at Cabauw originate from an inertial oscillation, which develops after sunset in a layer decoupled from the surface by stable stratification. The data are classified to different types of stable boundary layers by using the geostrophic wind speed and the isothermal net radiative cooling as classification parameters. For each of these classes, LLJ characteristics like frequency of occurrence, height above ground level, and the turning of the wind vector across the boundary layer are determined. It is found that LLJs occur in about 20% of the nights, are typically situated at 140-260 m above ground level, and have a speed of 6-10 m s(-1). Development of a substantial LLJ is most likely to occur for moderate geostrophic forcing and a high radiative cooling. A comparison with the 40-yr ECMWF Re-Analysis (ERA-40) is added to illustrate how the results can be used to evaluate the performance of atmospheric models
Original languageEnglish
Pages (from-to)1627-1642
JournalJournal of Applied Meteorology and Climatology
Volume48
Issue number8
DOIs
Publication statusPublished - 2009

Keywords

  • wind speed
  • boundary-layer meteorology
  • climatology
  • utrecht
  • atmospheric boundary-layer
  • southern great-plains
  • sloping terrain
  • kinetic-energy
  • united-states
  • wind
  • model
  • turbulence
  • intermittent
  • land

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