Turbulence Decay and Restratification in the Equatorial Ocean Surface Layer following Nighttime Convection

Abstract Although the process of restratification of the ocean surface layer at the equator following nighttime convection is similar in many ways to the process at midlatitudes, there are important differences. A composite day calculated from 15 days of consistent conditions at 140°W on the equator was compared with midlatitude observations by Brainerd and Gregg. In the depth range of 20–40 m, 1) minimum nighttime stratification was similar [N2 of 1.2–3.2 (× 10−6 s−2) vs 0.4–1.7 (× 10−6 s−2)], 2) maximum daytime stratification was significantly larger, as might be expected from the greater surface heat input [N2 of 8–21 (× 10−6 s−2 vs 3–7 (× 10−6 s−2)], and 3) minimum nighttime shear was similar [shear-squared was 1.4–4.6 (× 10−6 s−2) vs 0.8–1.9 (× 10−6 s−2)], but the maximum daytime shear was much larger [shear-squared of 24–41 (× 10−6 s−2) vs 3–7 (× 10−6 s−2)]. For much of the surface layer, the dominant identifiable cause of restratification in both cases was the divergence of the penetrating shortwav...