Department of Interior -- U.S. Geological Survey -- Woods Hole Field Center -- Plot Index Page

caption: Mass Bay current data graphs

Annual vector plots of low-pass filtered currents and wind stress

For each depth, the graphs show a row of current or wind stress vectors, their origins placed along the horizontal time axis so that the time series of currents may be shown. The length of each vector indicates speed or stress magnitude as shown on the vertical scales. The direction of the vector is the compass direction which the water or wind was flowing toward: up is north, right is east, etc.

Currents were measured with vector-measuring current meters (Weller and Davis, 1980) located 5 m below the sea surface and 10 m above the sea floor, and with a USGS tripod system with current sensors 1 m above the sea floor. In 1990 and 1991, the tripod current sensors were rotors and vanes like those used for vector averaging current meters. Starting in 1992, tripod systems used BASS acoustic current sensors (Williams, 1985).

Wind data were collected by the National Data Buoy Center. Wind stress was calculated from wind speed and direction measured at the large navigational buoy using the formulas of Large and Pond (1981).

Currents and wind stress were low-pass filtered using the PL33 filter (Flagg et al., 1976), which essentially removes all fluctuations having periods shorter than 33 hours.


This page is <URL:http://woodshole.er.usgs.gov/~fhotchki/caption_currents.html>.
Maintained by Fran Hotchkiss (fhotchkiss@usgs.gov)
Updated on 15 April 1997.