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Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami
MARCH 2011
During March 2011, 411 satellite-tracked surface drifting buoys, 58% 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. Very strong (~50 cm/s)
eastward anomalies were measured by a few near-equatorial drifters near 140W,
but the extent of this is not resolvable from the drifter array alone. Cold
SST anomalies of -0.5 to -1.5C were measured by most drifters east of 160W
from 20S to 20N, similar to the pattern seen in February.
During March 2011, 411 satellite-tracked surface drifting buoys, 58% 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. Very strong (~50 cm/s)
eastward anomalies were measured by a few near-equatorial drifters near 140W,
but the extent of this is not resolvable from the drifter array alone. Cold
SST anomalies of -0.5 to -1.5C were measured by most drifters east of 160W
from 20S to 20N, similar to the pattern seen in 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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