Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami
During March 2008, 307 satellite-tracked surface drifting buoys, 77% with
subsurface drogues attached for measuring mixed layer currents, were reporting
from the tropical Pacific. As seen last month, westward anomalies were
observed throughout most of the tropical Pacific basin, except in the region
0-8N, 120-140W. A number of drifters in this region exhibited strong eastward
anomalies, but were close together and may have been advected by a single
feature (e.g., a tropical instability wave) rather than reflecting a
larger-scale anomaly. Large scale westward anomalies along 10N were 20 cm/s,
as seen for many months now, and were 0-10 cm/s south of the equator. Cold SST
anomalies (-0.5 to -3.0C) persisted across the basin between 12S and 15N, while
most drifters south of 20S measured SST warmer than normal March values by +0.5
to +1.5C. Several drifters between 95W and the South American coast measured
SST warmer by +1.5 to +3.0C.
Top:Movements of drifting buoys in the tropical Pacific Ocean during mar08.
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.