Geostrophic drag law for conventionally neutral atmospheric boundary layers revisited

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Abstract

The geostrophic drag law (GDL), which predicts the geostrophic drag coefficient and the cross-isobaric angle, is relevant for meteorological applications such as wind energy. For conventionally neutral atmospheric boundary layers (CNBLs) capped by an inversion, the GDL coefficients A and B are affected by the inversion strength and latitude, expressible via the ratio of the Brunt–Väisälä frequency (N) to the Coriolis parameter (f). We present large-eddy simulations (LES) covering a wider range of N/|f| than considered previously, and show that A and B obtained from carefully performed LES collapse to a single curve when plotted against N/|f|. This verifies the GDL for CNBLs over an extended range of N/|f| within LES. Additionally, in agreement with atmospheric observations, we show that using A = 1.9 and B = 4.4 accurately predicts the geostrophic drag coefficient in the limit of weak inversion strength or high latitude ((Formula presented.)). However, due to the strong dependence of B on N/|f|, corresponding predictions for the cross-isobaric angle are less accurate. As we find significant deviations between the LES results and the original parameterization of the GDL for CNBLs, we update the corresponding model coefficients.

Original languageEnglish
Pages (from-to)847-857
Number of pages11
JournalQuarterly journal of the royal meteorological society
Volume147
Issue number735
DOIs
Publication statusPublished - 1 Jan 2021

Keywords

  • fluid dynamics
  • fluid mechanics
  • Drag law
  • Geostrophic
  • atmospheric boundary layer
  • large eddy simulations
  • Computational Fluid Dynamics
  • large-eddy simulation
  • latitude
  • geostrophic drag law
  • conventionally neutral atmospheric boundary layer
  • lapse rate
  • friction velocity
  • eddy simulation
  • large&#8208

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