Mesoscale Spiral Vortex Embedded within a Lake Michigan Snow Squall Band: High Resolution Satellite Observations and Numerical Model Simulations

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  • 1 San Francisco State University
  • | 2 R-SCAN Corporation, Minneapolis, Minnesota
  • | 3 National Center for Atmospheric Research, Boulder, Colorado
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Abstract

It is known that Great Lakes snow squall convection occurs in a variety of different modes on various factors such as air-water temperature contrast, boundary layer wind shear and geostrophic wind direction. An exceptional and often neglected source of data for mesoscale cloud studies is the ultrahigh resolution multispectral data produced by Landsat satellites. On 19 0ctober 1972, a clearly defined spiral vortex was noted in a Landsat-1 image near the southern end of Lake Michigan during an exceptionally early cold air outbreak over a still very warm lake. In a numerical simulation using a 3-D Eulerian hydrostatic equation mesoscale model (8 km grid, 36 × 46 × 11), with an initially uniform wind field, a definite analog to the observed vortex was generated. This suggests that intense surface heating can be a principal cause in the development of a low-level mesoscale vortex.

Abstract

It is known that Great Lakes snow squall convection occurs in a variety of different modes on various factors such as air-water temperature contrast, boundary layer wind shear and geostrophic wind direction. An exceptional and often neglected source of data for mesoscale cloud studies is the ultrahigh resolution multispectral data produced by Landsat satellites. On 19 0ctober 1972, a clearly defined spiral vortex was noted in a Landsat-1 image near the southern end of Lake Michigan during an exceptionally early cold air outbreak over a still very warm lake. In a numerical simulation using a 3-D Eulerian hydrostatic equation mesoscale model (8 km grid, 36 × 46 × 11), with an initially uniform wind field, a definite analog to the observed vortex was generated. This suggests that intense surface heating can be a principal cause in the development of a low-level mesoscale vortex.

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