A Study of Wave-Induced Effects on Sea Surface Temperature Simulations during Typhoon Events

Abstract

In this work, we investigate sea surface temperature (SST) cooling under binary typhoon conditions. We particularly focus on parallel- and cross-type typhoon paths during four typhoon events: Tembin and Bolaven in 2012, and Typhoon Chan-hom and Linfa in 2015. Wave-induced effects were simulated using a third-generation numeric model, WAVEWATCH III (WW3), and were subsequently included in SST simulations using the Stony Brook Parallel Ocean Model (sbPOM). Four wave-induced effects were analyzed: breaking waves, nonbreaking waves, radiation stress, and Stokes drift. Comparison of WW3-simulated significant wave height (SWH) data with measurements from the Jason-2 altimeter showed that the root mean square error (RMSE) was less than 0.6 m with a correlation (COR) of 0.9. When the four typhoon-wave-induced effects were included in sbPOM simulations, the simulated SSTs had an RMSE of 1 °C with a COR of 0.99 as compared to the Argos data. This was better than the RMSE and COR recovered between the measured and simulated SSTs, which were 1.4 °C and 0.96, respectively, when the four terms were not included. In particular, our results show that the effects of Stokes drift, as well as of nonbreaking waves, were an important factor in SST reduction during binary typhoons. The horizontal profile of the sbPOM-simulated SST for parallel-type typhoon paths (Typhoons Tembin and Bolaven) suggested that the observed finger pattern of SST cooling (up to 2 °C) was probably caused by drag from typhoon Tembin. SST was reduced by up to 4 °C for cross-type typhoon paths (Typhoons Chan-hom and Linfa). In general, mixing significantly increased when the four wave-induced effects were included. The vertical profile of SST indicated that disturbance depth increased (up to 100 m) for cross-type typhoon paths because the mixing intensity was greater for cross-type typhoons than for parallel-type typhoons.

Analysis of Wave-Induced Stokes Transport Effects on Sea Surface Temperature Simulations in the Western Pacific Ocean

“…In particular, the difference between RMSE without Stokes transport and that with Stokes transport is about 0.7 • C in Summer, while the difference in RMSE is about −1.0 • C in Autumn. This kind of behavior is probably caused by the tropical cyclones in Autumn [40]. Figure 12 shows a comparison of SST from the Argo and the sbPOM in 2012-2015.…”

“…Global sea surface temperature (SST) can be simulated using the sbPOM model [39]. This model was used to study SST cooling in the China Seas during the typhoon events [40]. Stokes drift enhances the shear instability of the upper ocean and strengthens the mixing effect at the air-sea layer, indicating that the Stokes drift affects the SST.…”

“…where H(x,y) is the bottom terrain, η(x,y,t) is the sea level fluctuation from the bottom (z = −H) to the sea surface (z = η), and σ ranges from −1 to 0. In the present work, the model has40 vertical sigma levels: [0, −0.0009, −0.0018, −0.0037, −0.0074, −0.0147, −0.0294, −0.0588, −0.0882, −0.1176, −0.1471, −0.1765, −0.2059, −0.2353, −0.2647, −0.2941, −0.3235, −0.3529, −0.3824, −0.4118, −0.4412, −0.4706, −0.5, −0.5294, −0.5588, −0.6176, −0.6471, −0.6765, −0.7059, −0.7353, −0.7647, −0.7941, −0.8235, −0.8529, −0.8824, −0.9118, −0.9412, −0.9706, −1]. The basic equations in the σ-coordinate system can be expressed as follows: , v, and ω represent the velocity under the σ-coordinates.…”

Cyclonic Wave Simulations Based on WAVEWATCH-III Using a Sea Surface Drag Coefficient Derived from CFOSAT SWIM Data

“…As an example, Figure 7a shows the case of the drag coefficient C d map using the re-fitted values in Equation (10). Note that the wind speeds are derived from a 0.1 • gridded composite wind field of Typhoon Lekima (2019) at 20:30 UTC on 1 October 2019.…”

“…In the last several decades, much effort has been devoted to this topic in numerous studies [3][4][5][6]. This is also an essential aspect for improving numerical wave models [7], e.g., WAVEWATCH-III (WW3) [8][9][10][11] and Simulating Waves Nearshore (SWAN) [12][13][14]. According to the study in [15], more than 300 typhoons have passed over the China Seas from 1998 to 2017, and typhoon-induced disasters pose increasingly serious threats to coastal areas of China.…”