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Composite structures of ocean temperature and salinity anomalies caused by tropical cyclones (TCs) or typhoons in the western North Pacific Ocean were obtained from Argo data. These structures were used to analyze ocean responses to typhoons and the dynamic mechanisms inherent in those responses with a particular focus on upwelling. TC-induced cooling is often strongly rightward-biased in the surface layer, and shifts toward the typhoon track at depths exceeding roughly 100 m. In the central water column within approximately 75 km of the typhoon track, subsurface warming predicted by vertical mixing is restrained and replaced by cooling due to upwelling. Upwelling contributes 15% on average to temperature cooling in the near surface layer (10–30 m), 84% in the subsurface layer (30–250 m) and 94% in the deep layer (250–600 m) during the period of 0.5–2.5 days after the typhoon's passage. It is suggested that the sea surface cooling effect of vertical mixing can be enhanced by the upwelling. The effect of upwelling is also prominent in the salinity response to typhoons. The composite results from the Argo data clearly reveal basic ocean responses to typhoons and indicate the important role of upwelling therein. [ABSTRACT FROM AUTHOR]

A high-resolution numerical model based on the Regional Ocean Modeling System (ROMS) was used to simulate the Yellow Sea Cold Water Mass (YSCWM) and revealed an extreme warm event of the YSCWM in the summer of 2007. This event was also captured by in situ observations. In August 2007, the average temperature of the YSCWM was above 1 °C higher than its climatological mean. The unusually-high temperature anomaly of the YSCWM could trace back to the winter 2006–07. Heat budget of the Yellow Sea deep water (YSDW) below 50 m depth, indicated that vertical mixing, rather than advection, in the winter 2006–07 played a crucial role in the generation of the warm event. With the seasonal thermocline disappearing in the winter 2006–07, a weak vertical mixing effect due to weak wind speeds and high heat content in the Yellow Sea upper water (YSUW) above the YSDW, together with strong advection effect, caused the YSDW to become quite warmer than its climatological mean. After that, the seasonal thermocline above the YSDW formed again and the warm YSDW persisted until the summer of 2007, resulting in the extreme warm event of the YSCWM. • An extreme warm event of the Yellow Sea Cold Water Mass (YSCWM) happened in the summer of 2007. • Vertical mixing, rather than advection, in the winter of 2006 played a crucial role in the generation of the warm event. • Weak vertical mixing effect, together with strong advection effect, made the YSCWM quite warmer than its climate state. [ABSTRACT FROM AUTHOR]

Volume transport through the Taiwan Strait during 2005–2008 was simulated using a shallow water model forced by high spatio-temporal resolution meteorological data. On average, simulated monthly mean transports ranged from a southward maximum of 0.38 Sv in December to a northward maximum of 2.02 Sv in June, with an annual mean northward transport of 0.78 Sv. These estimates are in agreement with the published results based on bottom-mounted ADCP observations. Several sensitivity experiments were conducted to separately examine possible influence of ignoring air pressure or applying time-averaged wind forcing on the transport estimate. We found that excluding the air pressure component in the model gave rise to an insignificant difference (0.01 Sv) in the mean transport estimate. Using multi-year-averaged monthly mean wind, however, provided markedly different results; it brought about a magnitude change of up to 0.65 Sv for the monthly mean transport and 0.34 Sv for the annual mean transport. The nonlinear parameterization of wind stress was mainly responsible for the distortion. In addition, we found that typhoons, as one kind of synoptic events, had an accumulative influence not only on the monthly mean transport during the typhoon season but also on the annual mean transport. The effect of typhoons reduced the monthly mean transport by up to 0.45 Sv and the annual mean transport by 0.09 Sv (more than 10%). Therefore, high temporal resolution wind data with synoptic scale variability are required to accurately estimate the monthly mean and annual mean transports when using a model. [ABSTRACT FROM AUTHOR]

Abstract: Volume transport in the Taiwan Strait is usually northward for most of the year and varies seasonally because of the adjustment of the East Asian monsoon. Based on model simulations, the influence on this northward transport of every typhoon formed during the period 2005–2009 was examined. The results showed that there were four typhoons which enhanced northward transport during these five years. The current measurements, obtained from a buoy deployed in the Taiwan Strait, matched these events exactly. These typhoons had special moving tracks and life histories. They traveled westward in the area south of the strait or moved northward from the south to the north. Under the influence of such a typhoon, the prophase southward atmospheric forcing in the strait was weak and the anaphase northward atmospheric forcing (mainly along-strait wind stress) was strong, which is necessary and crucial in enhancing the northward transport. The ageostrophic process, another important driving factor in transport change, was generated mainly by local atmospheric forces inside the strait under the typhoon weather conditions and its effect on transport magnitude was comparable to that of direct atmospheric forcing. It first stored some energy from the atmospheric forcing to restrain the transport change, and then released the stored energy to prolong and even to intensify the enhanced northward transport. [Copyright &y& Elsevier]

Abstract: A two-way nested coupled tide-surge prediction model was established and applied in the Taiwan Strait and adjacent sea area in this study. This two-dimensional (2D) model had a fine horizontal resolution and took into account the interaction between storm surges and astronomical tides, which made it suitable for depicting the complicated physical properties of storm surges in the Taiwan Strait. A two-way nesting technique and an open boundary condition developed from Flather''s radiation condition and Røed and Smedstad''s local mode idea, were successfully implemented in the model. A simulation experiment showed that the open boundary condition could be used in the coupled tide-surge model and that the performance of the two-way nested model was slightly superior in accuracy to that of the one-way nested one. The fluctuations of storm surge residuals with tidal period at Sansha and Pingtan tide stations during the period of typhoon Dan in 1999 were well reproduced by the model, with the coupling effect between storm surges and tides indicating that the effect of astronomical tides upon typhoon surges should be considered in a storm-surge prediction model for the Taiwan Strait. The forecast experiment during typhoon Talim in 2005 showed that the storm surge prediction outputs by the model were better in the early 20h of the forecast period of each model run than those in the later period due to the prediction accuracy of the typhoon track, maximum winds, and central air pressures. [Copyright &y& Elsevier]

The Taiwan Strait is the only direct passage between the South China Sea (SCS) and the East China Sea. Variations in the intensity of Kuroshio Branch and surface currents in the SCS result in seasonal and inter-annual variability in the hydrography of the SE Taiwan Strait, where the northwardly pointing funnel-like Penghu Channel is located. These currents vary with the intensity and direction of monsoons. The teleconnection between air-sea interaction of the east Pacific and west Pacific reportedly has time differences. The data in this study reveal that the salinity of the seawater in the Penghu Channel is highest during El Niño events with a seven-month lag to the monthly Niño 3.4 index, and lowest during La Niña periods, also with a lag of seven months to the monthly Niño 3.4 index. The chemical parameters also vary with these events. The concentrations of apparent oxygen utilization, nutrients, and hydrogen ions vary with the mixing ratio of SCS water and Kuroshio Branch water. The maximum concentrations of nutrients are significantly higher during the summer, seven months after a La Niña event (La Niña-7), than in other seasons. However, biological activities also affected these chemical parameters. In spring, active photosynthesis consumes more nutrients and hydrogen ion concentrations in La Niña-7 periods than in normal-7 periods. [ABSTRACT FROM AUTHOR]