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1992-08-21
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Date: Wed, 15 Jul 1992 19:19:14 PDT
From: Bill Lipa <lipa@camis.stanford.edu>
Subject: [*] Movie of ocean surface currents
When I'm not busy with Info-Mac, I consult for a small company that produces
radar systems for studying the oceans. Codar Ocean Sensors uses Macs equipped
with DSP cards to analyze the radar signals, creating real-time vector maps of
the ocean currents, as well as wind and wave data. The enclosed QuickTime
movie shows the currents in Monterey Bay from July 2 through 6. It works best
on 13" or larger displays with 256 colors.
The vectors represent currents at the surface, within the upper meter of the
ocean. They are measured at two-hourly intervals and interpolated in time to
give a smooth, movie-like appearance. As the range of the radars varies due to
changing environmental noise, interference, and the sea state, the edge of
the coverage area furthest out to sea appears to move in and out in an
irregular fashion.
Some recurring effects and patterns are worth noting:
- There is a strong surface flow from the north/northwest most summer
afternoons, peaking around 1800. This is due to the midday westerly
(onshore) winds, forcing currents to veer to the right by the
Coriolis-Ekmann effect.
- When the winds weaken at night, a counter-clockwise gyre northwest of
Moss Landing can sometimes be seen, recurring with the tidal period of
25.9 hours, for example at 2000 on July 2 or 0000 July 4.
Bill Lipa
lipa@camis.stanford.edu