Analytical and Cloud Model Analysis of Vertical Vorticity Generation by Terrain

Analytical and Cloud Model Analysis of Vertical Vorticity Generation by Terrain

by Terrence J. Corrigan and Steven Businger

University of Hawaii at Manoa

Arctic cyclogenesis often starts near complex terrain surrounding the Arctic Ocean. We argue that the deepening rate for Arctic Cyclones is a function of the total rate of change of the vertical vorticity over time times a latitude scaling factor associated with the Coriolis force. This study explores the potential of terrain for generating vertical vorticity that contributes to Arctic cyclogenesis through upscale growth facilitated by tropospheric polar vortices. There are five components of the vorticity equation that will be evaluated for various terrain configurations using the CM1 cloud model.

1. Orographic vertical advection of vertical vorticity gradients.
2. Lee Cyclogenesis.
3. Veering shear redirected into the vertical by terrain to create vertical vorticity.
4. Unidirectional shear impacting a concave cirque to create a pair for vertical vortices of opposite sign.
5. Growth of vertical vorticity when the mean wind shear is orthogonal to the terrain.