Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami
APRIL 2011
During April 2011, 415 satellite-tracked surface drifting buoys,
61% with subsurface drogues attached for measuring mixed layer currents,
were reporting from the tropical Pacific. As seen since September 2010,
the westward SEC was stronger than normal, with westward anomalies of
O(10 cm/s) present in a broad latitude range from 5-20S. Between 10-20N,
the westward NEC was also faster than average by ~5 cm/s. Cold SST
anomalies of -0.5 to -1.5C were measured by many drifters east of 160W
from 20S to 20N, a pattern seen since February.

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 1993-2010 (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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