Abstract:
These monthly climatologies were prepared by G. Meehl and are archived
at the National Center for Atmospheric Research (NCAR). G. Meehl
prepared a 5 X 5 degree latitude/longitude dataset of long-period
ocean currents speed and direction based on pilot charts covering the
world ocean southward to about 50 S. The pilot charts are based on
summaries of ship drift data. One of the charts was updated
... about
1984, after the tape data was prepared. The digital data is available
for January, April, July, and October representing the four seasons.
Meehl (1982) decided to use pilot charts in constructing an observed
seasonal source of global ocean surface currents. These charts are
prepared by the U.S. Naval Oceanographic Office (NAVOCEANO), and
among numerous other quantities, arrows on these charts show surface
current directions labeled with current speeds in either knots or
nautical miles per hour. Data for the pilot charts are based on
long-term mean current speeds and directions already derived from the
NAVOCEANO shipdrift file. A ship drift is the difference between its
true position and its predicted position calculated 24 hours earlier
by dead reckoning; this difference can be attributed to wind and ocean
currents. This data set provides the flexibility needed to produce a
source of observed surface currents in a suitable format for use in
ocean model and diagnostic studies. 
