How is Salinity Stratification Affected by Surrounding Precipitation Variability?
[12-Feb-2018] Thompson, E.J., Drushka, K., Asher, W., Jessup, A.T., Schanze, J.J., and Clark, D.
Presented at the 2018 Ocean Sciences Meeting
This study seeks to understand the impact of spatially and temporally varying rainfall on local salinity stratification. Previous observational studies have demonstrated a positive correlation between maximum salinity stratification and maximum rain rate when wind speed is constant. However, local rain rate and wind speed do not provide sufficient information to completely explain local salinity stratification measurements. For instance, measurements made during the 2016 and 2017 SPURS-2 field campaigns in the tropical eastern Pacific show that maximum rain rate and maximum salinity stratification are not always coincident. Furthermore, salinity stratification has been observed without local rainfall being present. We find that ocean surface freshening is affected by local rainfall as well as upstream rain accumulation, which can be advected toward in situ salinity sensors. It is not known how the spatial extent and spatiotemporal variability of a precipitation event affect the generation of salinity stratification or maximum salinity stratification, or the timing of that maximum relative to the maximum in local rainfall.
Here, we synthesize observations made during the 2016 and 2017 SPURS-2 field campaigns in the tropical eastern Pacific. Scanning X-band radar observations of rain are used to deduce the spatial extent of precipitation events and the spatiotemporal variability of rain intensity surrounding the research ship. A salinity snake and underway salinity profiling system (USPS) provide measurements of salinity as a function of depth from 0-5 meters at the ship and a towed surface salinity profiler measured salinity gradients in the upper meter within 100 m of the research ship. We examine numerous individual rain events to determine how the magnitude and timing of salinity stratification is related to the size, intensity, and spatial variability of precipitation.