Observation and Modeling of Rain-Induced Near Surface Salinity Anomalies
[13-Nov-2014] Asher, W., Jessup, A., and Drushka, K.
Presented at the 2014 Aquarius/SAC-D Science Team Meeting
Precipitation on the ocean forms salinity and temperature gradients in the top few meters of the ocean surface. If present, these gradients will complicate comparing salinity measured by ARGO drifters at typical depths of five meters to salinities retrieved using L-band microwave radiometers such as Aquarius and SMOS at depths on the order of 0.01 m. Therefore, understanding the spatial scales and temporal persistence of these gradients, and the conditions under which they form, will be important in calibrating satellite measurements of sea surface salinity. A towed, surface-following profiler was deployed from the R/V Kilo Moana in December of 2011 in the central tropical Pacific Ocean. The profiler measured temperature and conductivity at depths of 10 cm, 20 cm, and 100 cm, and 200 cm. Profiles of temperature and conductivity in the presence of rain show that rain both freshens and cools the ocean surface. This provides opposite forcing for the density gradient at the surface, and depending on the rain rate the density profile can be either stable (freshening dominated) or unstable (cooling dominated). The dynamics of this are investigated using a one-dimensional model of ocean surface turbulence.