Rain and Sun Create Slippery Layers in the Eastern Pacific Fresh Pool

Abstract

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The Impact of Rain on Ocean Surface Waves and Currents

“…It was at this point that the rain rate dropped to less than 10 mm/hr by the rain gauge's measure and ring waves became nearly imperceptible in the short wave slope fields (Figure d). One potential explanation for this series of events is that the rain event created a slippery layer (Kudryavtsev & Soloviev, ; Shcherbina et al, ), which allowed the impulsive wind to rapidly accelerate the near‐surface flow. Once the rain had subsided, the wind forcing worked to mix the slippery layer back into the saline upper ocean, reducing the near‐surface current magnitude.…”

“…Once the rain had subsided, the wind forcing worked to mix the slippery layer back into the saline upper ocean, reducing the near‐surface current magnitude. This explanation requires the full development and extinguishment of a slippery layer within 5 min time under high levels of wind forcing, an outcome which is unlikely based on many measurements of such layers' development (Dong et al, ; Doeschate et al, ; Thompson et al, ; Shcherbina et al, ; Volkov et al, ). The spectral growth rate shown in Figure c is likely the key to understanding this observed sequence of events.…”

“…It is understood that rainfall on the ocean creates a thin, highly turbulent fresh lens near the surface (Harrison & Veron, ; Peirson et al, ; Zappa et al, ), which enhances air‐sea flux but temporarily stalls vertical mixing (Ho et al, ; Schlüssel et al, ; Zappa et al, ). Under low levels of wind forcing, this lens—often several meters thick—forms what is known as a “slippery layer” (Anderson et al, ; Kudryavtsev & Soloviev, ), accelerating past the saline water at the base of the lens (Shcherbina et al, ; Wijesekera et al, ). This phenomenon has been extensively studied and documented in the literature—particularly in recent years (e.g., Doeschate et al, ; Dong et al, ; Drushka et al, ; Volkov et al, ; Shcherbina et al, ; Thompson et al, ).…”

“…Under low levels of wind forcing, this lens—often several meters thick—forms what is known as a “slippery layer” (Anderson et al, ; Kudryavtsev & Soloviev, ), accelerating past the saline water at the base of the lens (Shcherbina et al, ; Wijesekera et al, ). This phenomenon has been extensively studied and documented in the literature—particularly in recent years (e.g., Doeschate et al, ; Dong et al, ; Drushka et al, ; Volkov et al, ; Shcherbina et al, ; Thompson et al, ). This fresh lens is typically tens of centimeters thick, with turbulent kinetic energy dissipation falling orders of magnitude over the upper half meter of the water column (Zappa et al, ).…”

The SPURS-2 Eastern Tropical Pacific Field Campaign Data Collection

“…This fact renders traditional Lagrangian methods less effective, as drifters placed into the region have very short residence times. The Lagrangian frame experiment, making use of Seagliders and Wave Gliders to follow the motion of a neutrally buoyant float (Shcherbina et al, 2019, in this issue), was set up to finesse this issue. Heavy rainfall, the principal reason for conducting SPURS-2 in this region, is patchy and difficult to sample, necessitating the use of sophisticated rain radar (Rutledge et al, 2019, in this issue).…”