Analytical description of a nocturnal low-level jet

Authors

  • Alan Shapiro,

    Corresponding author
    1. School of Meteorology, University of Oklahoma, Norman, Oklahoma, USA
    2. Center for Analysis and Prediction of Storms, University of Oklahoma, Norman, Oklahoma, USA
    • School of Meteorology, University of Oklahoma, 120 David L. Boren Blvd., room 5900, Norman, OK 73072, USA.
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  • Evgeni Fedorovich

    1. School of Meteorology, University of Oklahoma, Norman, Oklahoma, USA
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Abstract

An exact analytical solution of the equations of motion is presented for the Blackadar conceptual model of the nocturnal low-level jet as an inertial oscillation arising from the sudden release of frictional constraint (near-cessation of dry-convective turbulent mixing) near sunset. The jet is modelled as a transient one-dimensional boundary-layer phenomenon, with the release of frictional constraint emulated by an impulsively reduced mixing coefficient (eddy viscosity). Prior to the reduction, the flow is in an equilibrium state described by the classical steady-state Ekman solution. The dimensional parameters of the transient problem are the Coriolis parameter, the post- and pre-sunset eddy viscosities, and an imposed pressure gradient force. The corresponding non-dimensional problem is governed by a single parameter, the ratio of the post- and pre-sunset mixing coefficients. The solution is obtained by the method of Laplace transforms. Copyright © 2010 Royal Meteorological Society

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