Abstract
Numerous examples of meso-beta scale (20-200 km) eddies in the marine boundary layer environment off the U.S. west coast, such as the Catalina Eddy, have appeared in the literature, as has satellite imagery of even smaller (small end of the meso-beta scale to the large end of the meso-gamma scale) von Karman vortices downwind of islands. This paper presents unique photographic evidence of two eddies of meso-gamma scale (2-20 km) in the marine stratocumulus near the California coast. One occurred downwind of Catalina Island, while the other was observed just offshore from Grover Beach, downwind of a headland to the northwest. The photos were taken by pilots flying commercial routes between Santa Ana and San Francisco. Marine boundary layer eddies of this size are likely to escape detection by most means but aerial photography, yet they are likely to play a role in lateral mixing at the coastal margin. With horizontal dimensions of 10 km and a 1 km cloud free "eye," they are too small to show up clearly in geostationary satellite imagery that has been used to identify some of the larger vortices. On the other hand, they may not be clearly visualized as a circulation by a surface-based observer, especially since they are found in a marine stratocumulus environment where there are few or no atmospheric measurements. Pilots of commercial airlines, with a wide view of the horizon, and an altitude that gives a relatively large-scale view of features below, may be the most likely avenue for detection of eddies such as those shown here. This submission presents these images in the interest of documenting the physical characteristics of eddies falling between the more commonly observed meso-beta and those smaller scales more traditionally thought to encompass turbulence. A preliminary mesoscale model simulation with 250 m horizontal resolution is employed to elucidate the causes for one of the eddies. We use the model output to describe and understand characteristics of the flow field in which the eddy occurred, and to determine the origins of the cyclonic vorticity apparent in the aerial image.
Original language | American English |
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State | Published - Dec 2007 |
Externally published | Yes |
Event | American Geophysical Union Fall Meeting - San Francisco, CA Duration: Dec 1 2013 → … |
Conference
Conference | American Geophysical Union Fall Meeting |
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Period | 12/1/13 → … |
Keywords
- Boundary layer processing
- mesoscale meteorology
- regional modeling
Disciplines
- Atmospheric Sciences
- Meteorology