Comparing Spatial Scales of IMERG Rain with Depth-Resolved Near-Surface Salinity Structure as Measured During the SPURS-2 Experiment
[16-Dec-2016] Asher, W., Thompson, E.J., Drushka, K., Jessup, A.T., and Schanze, J.J.
Presented at the 2016 AGU Fall Meeting
Salinity stratification in the ocean due to rain affects the spatial and temporal variability of heat, salinity, and momentum in the near-surface layer of the ocean. However, the relative importance of rain in driving surface variability of the ocean is not fully understood because routine observations have not been able to quantify either the spatio-temporal variability of rain or the response of the underlying ocean to rain. Relatively high resolution (10 km, 30 min) NASA GPM IMERG rain rate data, now available over much of the globe, can be used with in situ measurements of temperature and salinity in the upper few meters of the ocean to understand how rainfall patterns over scales of tens to hundreds of kilometers are related to spatial variability in the ocean. In this study, local and integrated upstream satellite-derived rain accumulation are compared to the horizontal variability of vertical gradients of temperature and salinity measured between the surface, 2 m, 3 m, and 5 m during the 2016 SPURS-2 experiment in the eastern Pacific Ocean. Continuous underway measurements of temperature and salinity at each depth along the ship's track provide a large sample size of salinity and temperature stratification events due to rain and/or diurnal warming. The variability in the upper ocean due to these processes is cross-correlated with precipitation events at and/or just upstream of the in situ measurements to determine how rainfall is correlated with salinity variations. Because the vertical salinity gradients can be calculated as a function of depth across the upper five meters, the temporal lag in the correlation between dS/dz and rainfall can be used to infer information about vertical mixing in the upper ocean.