Abstract
Multi-year records of satellite remote sensing of sea surface salinity (SSS) provide an opportunity to investigate the climatological characteristics of the SSS response to tropical cyclones (TCs). In this study, the influence of TC winds, rainfall and preexisting ocean stratification on SSS evolution is examined with multiple satellite-based and in-situ data. Global storm-centered composites indicate that TCs act to initially freshen the ocean surface (due to precipitation), and subsequently salinify the surface, largely through vertical ocean processes (mixing and upwelling), although regional hydrography can lead to local departure from this behavior. On average, on the day a TC passes, a strong SSS decrease is observed. The fresh anomaly is subsequently replaced by a net surface salinification, which persists for weeks. This salinification is larger on the right (left)-hand side of the storm motion in the Northern (Southern) Hemisphere, consistent with the location of stronger turbulent mixing. The influence of TC intensity and translation speed on the ocean response is also examined. Despite having greater precipitation, stronger TCs tend to produce longer-lasting, stronger and deeper salinification especially on the right-hand side of the storm motion. Faster moving TCs are found to have slightly weaker freshening with larger area coverage during the passage, but comparable salinification after the passage. The ocean haline response in four basins with different climatological salinity stratification reveals a significant impact of vertical stratification on the salinity response during and after the passage of TCs.
Highlights
Tropical cyclones (TCs) are one of the most destructive natural hazards, in terms of human and financial costs
Using Soil Moisture Active-Passive (SMAP) swath daily raw data, the Lagrangian composite sea surface salinity (SSS) anomaly
We further explored the influence of TC translation speed on surface salinity response
Summary
Tropical cyclones (TCs) are one of the most destructive natural hazards, in terms of human and financial costs. Characterizing and understanding the upper ocean response to TCs are important steps for understanding the air-sea interaction during the passage of TCs and the improvement of TC intensity forecasts Both observational and modeling studies have shown that TCs drive strong vertical mixing and upwelling, which leads to surface cooling by entrainment of colder subsurface waters [8,9,10,11,12,13]. As will be shown below, looking across many TCs, the surface salinity response is initially dominated by the TC rainfall and subsequently by vertical ocean processes To complement these case studies, we seek to describe the climatological characteristics of the ocean haline response to TCs and compare the salinity changes with the ocean temperature response, through a combined analysis of satellite and in-situ observations.
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