On the characteristics of eddies in the stable atmospheric boundary layer

✍ Scribed by J. M. Rees

• Publisher: Springer
• Year: 1991
• Tongue: English
• Weight: 890 KB
• Volume: 55
• Category: Article
• ISSN: 0006-8314
• DOI: 10.1007/bf00119808

✦ Synopsis

A discussion of the cross-spectral properties of eddies in the lowest 40m of the nocturnal boundary layer is presented. The study involves the analysis of meteorological data collected by the British Antarctic Survey at Halley Station, Antarctica, during the austral winter of 1986. Cross-spectral analysis is used to determine whether the nature of the observed eddies is primarily turbulent or whether their structure is characteristic of ,qoherent internal gravity waves. It is found that the crossspectral phases indicate the presence of turbulent eddies only when the local gradient Richardson number (Ri) is less than the critical value of l/4. Trapped modes were only observed when an offshore wind prevailed, indicating that topographic effects are responsible for their generation. The relative phases of velocity and temperature were often observed to change with height. This can be explained by examining the underlying meteorological conditions. On several occasions, regions of counter-gradient fluxes were detected. A physical explanation of this phenomenon is proposed.