Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami
DECEMBER 2009
During December 2009, 407 satellite-tracked surface drifting buoys, 76%
with subsurface drogues attached for measuring mixed layer currents,
were reporting from the tropical Pacific. Dramatic eastward anomalies
of 50-70 cm/s were measured by many equatorial drifters in the central
part of the basin, with anomalies as high as 80cm/s in the longitude
band 160W to the dateline. This El Nino pattern was associated with hot
equatorial SST anomalies of +1.5 to +3.0C from 130W to 180. Outside of
the equatorial band, and west of about 110W, most drifters measured warm
(+0.5 to +1.5C) SST anomalies. Slightly cold SST anomalies (-0.5 to
-1.5C) were observed in the southeasternmost corner of the domain as in
the previous month.

FIGURE A1.1
a) Top: Movements of drifting buoys in the tropical Pacific Ocean.
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 blue.
b) 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.
c) Bottom: Anomalies from the climatological monthly mean currents for this month.
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