Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami
At the beginning of September 2005, 468 satellite-
tracked surface drifting buoys, 89% with subsurface
drogues attached for measuring mixed-layer currents,
were reporting from the tropical Pacific. Drifters
in the westward SEC - between the equator and 10S -
moved anomalously quickly, 10-20 cm/s faster than
the climatological mean speed of this current. This
anomaly was apparent across the basin east of the
dateline. An intense NECC may be due to the
drifters advected eastward on the northern edge of
strong instability waves along 120-150W. Due to a
gap in coverage along and immediately north of the
equator in this band, the structure of these TIWs
is poorly sampled. The westward NEC is anomalously
strong at 10-15N, 150W-160E, but is elsewhere close
to its climatological strength. Many of the drifters
in the region 5N-15S, 160E-160W measured anomalously
warm SSTs (+0.5-1.5C). North of 5N in this
longitude band, SSTs were very close to climatology.
To the east, equatorial SSTs were typically at or
slightly (~1C) above normal August values.
Top:Movements of drifting buoys in the tropical Pacific Ocean during aug05.
The linear segments of each trajectory represent a one week displacement.
Trajectories of buoys which have lost their subsurface drogues are gray; those with
drogues are black.
Middle: Monthly mean currents calculated from all buoys 1993-2002 (gray),
and currents measured by the drogued buoys this month (black) smoothed by an
optimal filter.
Bottom: Anomalies from the climatological monthly mean currents for this month.