The intensity simulation of tropical cyclones (TCs) has been a long‐standing challenge for numerical models, and an accurate sea surface roughness (z0 ${z}_{0}$) parameterization scheme is the key to enhance the intensity prediction. In our study, a new z0 ${z}_{0}$ parameterization scheme (SD21) is proposed and applied in the Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport model to simulate two super typhoons. The SD21 takes into account both the wave state and sea foam, and it is suitable for low to extreme wind conditions. The results of the eight numerical experiments show that the TC intensity and structure are sensitive to the choice of z0 ${z}_{0}$ parameterization schemes. Compared with the widely used z0 ${z}_{0}$ parameterization schemes, the SD21 scheme presents much better results in the simulation of the intensity and intensification speed of strong TCs. Notably, the simulation of the wind speeds generated by the SD21 is more compatible with the best track data and significantly better than that of the other schemes. Furthermore, we find that the wave state and sea foam remarkably affect the magnitude and spatial distribution of z0 ${z}_{0}$, the following two conclusions are obtained: (a) The z0 ${z}_{0}$ parameterization that takes into account the wave state can reduce the excessive roughness at the TC periphery and restrict the high‐value area of the roughness to the TC‐core region. (b) The sea foam significantly decreases the roughness value in areas with 10 m wind speeds above 40 m/s.
Due to the lack of observational data, the understanding of propagation characteristics of temperature anomaly is mainly concentrated in the sea surface and the waters above thermocline. Little is known about the propagation characteristics of temperature anomaly in the middle and deep oceans. Based on the gridded Argo data, we analyze the propagation characteristics of temperature anomaly along the isodensity. We found that the temperature anomalies in the middle and deep ocean layers propagate westward at most latitudes, which is the same direction as the propagation of the surface temperature anomaly caused by oceanic Rossby waves. Through the Radon transform, we determined the propagation speeds on different isodensities and explored the relationship of propagation speeds and latitudes and water depth. To the best of our knowledge, this study is the first to explore the propagation characteristics of mid-deep temperature anomalies at the ocean basin scale.
The prediction of tropical cyclone (TC) intensity has been a lasting challenge. Numerical models often underestimate the intensity of strong TCs. Accurately describing the air–sea heat flux is essential for improving the simulation of TCs. It is widely accepted that sea spray has a nonnegligible effect on the heat transfer between the atmosphere and the ocean. However, the commonly used sea spray-induced heat flux algorithms have poor applicability under high wind speeds, and it is difficult to apply these algorithms to models to forecast TCs. In this study, we proposed an improved sea spray-induced heat flux algorithm based on the FASTEX dataset. This improved algorithm performs much better under high wind speed conditions than the commonly used algorithms and can be used in a coupled numerical model. The addition of sea spray-induced heat fluxes noticeably enhances the total air–sea heat fluxes and allows more energy to be transferred from the ocean to the lower atmosphere. In the simulation of TCs, the addition of sea spray-induced heat fluxes significantly improves the simulation of TC intensity and makes the low-pressure structure and wind field structure more fully developed in the horizontal direction.
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