Possible Connections between Satellite Precipitation and Saildrone Sea Surface Salinity Observations of Tropical Cyclones

NOAA’s Saildrone Hurricane Observation mission in 2021 provided real-time, in-situ data of a variety of atmospheric and oceanic parameters, including sea surface salinity. This study explores possible connections between saildrone observations of surface salinity from this mission and rainfall measurement by satellites. For this investigation, gridded satellite precipitation data from CMORPH was interpolated on to saildrone locations using the Haversian distance formula and weighted averaging to generate paired salinity and precipitation data that are collocated at a given time. Comparisons were made using daily, hourly, and 30-minute precipitation data and salinity observations from 5 saildrones that intercepted 6 different tropical cyclones over 90 days. In some cases, particularly during short intervals in which saildrones were in close proximity to tropical cyclones, evidence was found that large rainfall led to a quick reduction in surface salinity, as expected. For the remaining tropical cyclones, however, which were associated with much higher wind speeds, a large decrease in rainfall led to a quick increase in surface salinity. Thus, in general, the relationship between precipitation and salinity is not always obvious. This suggests that there are other factors that influence surface salinity variability. Such factors include advection by currents, vertical mixing, and wind speed.