Advertisement

Boundary-Layer Meteorology

, Volume 63, Issue 4, pp 397–423 | Cite as

An analytical study of diurnal wind-structure variations in the boundary layer and the low-level nocturnal jet

  • M. P. Singh
  • Richard T. McNider
  • J. T. Lin
Article

Abstract

An analytical framework is proposed for studying variations in the diurnal wind structure in the planetary boundary layer (PBL) and the evolution of the low-level nocturnal jet. A time-dependent eddy-diffusivity coefficient corresponding to solar input is proposed, and an appropriate coordinate transformation ensures that mixing height varies continuously with ground heat-flux changes. The solution exhibits the receding character of the daytime PBL as evening approaches, thereby dividing the PBL into two regimes — the one just above the ground, representing the nocturnal boundary layer, and the region above it. It is assumed that inertial oscillations (IO) are triggered in the upper layer at about the time of sunset when the reversal in the direction of ground heat flux is felt in the upper layer. Two approaches are adopted to determine the characteristic features of IO and the evolution of the nocturnal low-level jet. The first one is based on the physical principle that release of horizontal momentum due to deviation from the geostrophic wind gives rise to the IO. The solution captures all the characteristic features of the IO, such as phase shift and decreasing amplitude of the IO with increasing height. According to this analysis the IO is triggered at a level as soon as the top of the receding boundary layer leaves that level. The solution is discontinuous with respect to the vertical coordinate. In the second approach we solve an initial-value problem to determine the solution in the upper layer, assuming that at about the time of sunset there is a rapid collapse of the daytime PBL to the steady, nocturnal boundary layer. The assumption is based on the mixing-height profiles prepared from climatological data collected at Delhi. The solution for the nocturnal boundary-layer regime is then obtained as a boundary-value problem. The solutions so obtained are continuous throughout the domain of interest and exhibit the characteristic features of an IO. The analysis leads to the conditions under which a low-level nocturnal jet is produced and provides quantitative estimates of the parameters, such as length of night, latitude, mixing height at sunset and nocturnal mixing height, that are conducive to the generation of a jet. The nocturnal wind profile produced by this approach compares well both with typical atmospheric data observed at Delhi and with output from a mesoscale numerical model. There is still some uncertainty related to the time of initiation of the IO as a function of latitude.

Keywords

Planetary Boundary Layer Wind Profile Geostrophic Wind Wind Structure Inertial Oscillation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Blackadar, A. K.: 1957, ‘Boundary-Layer Wind Maxima and Their Significance for the Growth of the Nocturnal Inversion’,Bul. Amer. Meteorol. Soc. 38, 283–290.Google Scholar
  2. Blackadar, A. K. and Buajitti, K.: 1957, ‘Theoretical Studies of Diurnal Wind Struture Variations in the Planetary Boundary-Layer’,Quart. J. Roy. Meteor. Soc. 83, 486–500.Google Scholar
  3. Holzworth, G. C.: 1967, ‘Mixing Depths, Wind Speed and Air Pollution Potential for Selected Locations in the U.S.A.’,J. Appl. Meteorol. 6, 1039–1044.Google Scholar
  4. Manju Kumari: 1985, ‘Diurnal Variation of Mean Monthly Mixing Depths for the City of Delhi’,Mausam 36, 71–74.Google Scholar
  5. McNider, R. T. and Pielke, R. A.: 1981, ‘Diurnal Boundary-Layer Development over Sloping Terrain’,J. Atmos. Sci. 38, 2198–2212.Google Scholar
  6. McNider, R. T., Moran, M. D. and Pielke, R. A.: 1988, ‘Influence of Diurnal and Inertial Boundary-Layer Oscillations on Long-Range Disperson’,Atmos. Environ. 11, 2445–2462.Google Scholar
  7. McNider, R. T., Lin, J. T. and Singh, M. P.: 1992, ‘Diurnal Wind-Structure Variations and Dispersion of Pollutants in the Boundary-Layer’, Submitted for publication toAtmos. Environ.Google Scholar
  8. Paegle, J.: 1970, ‘Studies of Diurnally Periodic Boundary Layer’, Winds. Tech. Rep. to NSF, University of California.Google Scholar
  9. Shirvaikar, V. V.: 1975, ‘Generation of Very High Supergeostrophic Winds using a New Form of Oscillating Eddy Viscosity Profile in a Barotropic P.B.L.’,Indian J. Meteorol. Hydrol. & Geophys. 26(3), 334–344.Google Scholar
  10. Thorpe, A. J. and Guymer, T. H.: 1977, ‘The Nocturnal Jet’,Quart. J. Roy. Meteorol. Soc. 103, 633–653.Google Scholar

Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • M. P. Singh
    • 1
  • Richard T. McNider
    • 1
  • J. T. Lin
    • 1
  1. 1.Mathematical Science DepartmentUniversity of Alabama in HuntsvilleHuntsvilleUSA

Personalised recommendations