Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami

During June 2007, 346 satellite-tracked surface drifting buoys, 68% with subsurface drogues attached for measuring mixed layer currents, were reporting from the tropical Pacific. Strong (~30 cm/s) westward anomalies were measured by a large number of drifters at 5-10N, 150W to 150E, a broader region than seen last month. Weaker westward anomalies of 10-20 cm/s were exhibited across the basin, from 20N to 20S, by much of the array. Five drifters at 6-8N, 130-136W exhibited eastward anomalies associated with advection at the northern edge of the instability wave train. As in May, most drifters north of the equator and east of the dateline measured SSTs near normal seasonal values, although many exhibiting westward current anomalies also measured SSTs colder by -0.5 to -1.5C. South of the equator and west of 130W, the majority of drifters measured SSTs of +0.5 to +1.5C above typical June values.

Top:Movements of drifting buoys in the tropical Pacific Ocean during jun07. 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.