Variabilities in sea-surface temperature and size of the Western Pacific Warm Pool were tracked with 10 years of satellite multichannel sea-surface temperature observations from 1982 to 1991. The results show that both annual mean sea-surface temperature and the size of the warm pool increased from 1983 to 1987 and fluctuated after 1987. Possible causes of these variations include solar irradiance variabilities, EI Niño-Southern Oscillation events, volcanic activities, and global warming.

The wake of Green Island was investigated in the alongshore flowing Kuroshio east of Taiwan, where current speeds range from 1 to 1.5 ms–1. Vertical profiling with shipboard lowered acoustic Doppler current profiler and conductivity‐temperature‐depth profiler revealed sizable anomalies in flow and water characteristics in the lee of Green Island. Two different stages of wake evolution were observed from two shipboard surveys. In the first stage, a recirculation developed leeward of the island, followed by a wavy (wave‐like) tail that resembled a weak vortex street. In the second stage, a cold eddy probably originating from the leeward side of the island showed up 14 km downstream of the island. The wake water was colder, saltier, higher in chlorophyll‐a concentration, and produced isopycnal doming up to 60 m. In the recirculation area, the relative vorticity, either positive or negative, was 10 times of planetary vorticity, and the horizontal divergence or convergence was O (10–4 s–1) on average. Flow divergence and convergence in the wake were expected to form upwelling and downwelling zones, producing a vertical circulation that vertically displaces isotherms. High inverse Richardson number, produced by strong vertical shear of horizontal currents, was associated with intense overturning events in the wake. High vertical shear of horizontal currents drove the mixing. The dissipation rate of turbulent kinetic energy in the overturn regions is O (10–7–10–5) W Kg–1; the corresponding eddy diffusivity is O (10–3–10–1) m2 s–1. The wake water properties are vertically diffused via upwelling and turbulence and can be delivered downstream through eddy shedding or advection. The extent of downstream influence remains to be investigated.

[1] This study analyzes the effects of thermocline shoaling on the ocean internal wave (IW) generation in the north South China Sea (NSCS). Seven years of satellite synthetic aperture radar (SAR) images from 1995 to 2001 are used for the statistical analysis of IW occurrence, and field measurements of sea surface wind, sea state, and vertical temperature profiles are used for analyzing IW generation and SAR imaging conditions. Latitudinal distribution of IW packets shows that 22% of IW packets distributed in the east of 118°E obviously originate from the Luzon Strait, and 78% of IW packets west of 118°E may propagate from the east or evolve into the solitons originating from the east boundary owing to the fission effect of shoaling thermocline. The yearly distribution of IW occurrence frequencies reveals an interannual variability, implying that there are long-term and large-scale processes modifying the SAR-observed IW occurrence. The monthly SAR-observed IW occurrence frequencies show that the high frequencies are distributed from April to July and reach a peak in June with a maximum frequency of 20%. The low occurrence frequencies are distributed in winter from December to February of next year with a minimum frequency of 1.5% in February. This study proposes that the IW generation needs the necessary and sufficient conditions: initial disturbance formation and wave amplitude growth. Owing to the dissipation effect on the initial disturbance, only fully grown waves have a chance to radiate out of the source region. A physical model and PKdV equation are adopted for analyzing the sufficient conditions for solitary IW amplitude growth. The results indicate that the thermocline shoaling provides the forcing to soliton amplitude growth, so that the soliton amplitude growth ratio (SAGR) serves as a decisive factor for the IW occurrence frequency. Theoretical analysis predicts a linear relation between the two. Application of theoretical models to field measurements in the Luzon Strait gives a correlation coefficient as high as 0.845 with a confidence level of 99% for months from March to November. The linear regression gives a correlation coefficient (R 2 ) of 0.6519 and a SAGR threshold (minimum) value of 0.90 for IW occurrence. According to the theoretical solutions, the eastward propagating disturbances have no chance to grow up, so that they hardly appear on the east side of the submarine ridges in the eastern Luzon Strait.

[1] This study investigates upper ocean response to Super Typhoon Hai-Tang, the most intense typhoon in 2005, in the western North Pacific using multi-satellite microwave data, typhoon data and Argo profiles. Sequential merged microwave sea surface temperature (SST) images show that Hai-Tang induced four separately cooling responses after its trail in the western North Pacific during 11 -18 July.Comparison between upper ocean responses of cooling SST and pre-typhoon sea surface height suggests that these cooling responses of the upper ocean to Hai-Tang are closely associated with pre-existing cyclonic circulation denoted by pre-existing negative sea surface features. Furthermore, applying Argo profiles, the physical mechanism is confirmed to be associated with pre-existing cyclonic circulations provide a relatively unstable thermodynamic structure, and therefore cold water would be brought up readily. This paper provides the rather convincing evidence that cyclonic flow and uplifted thermocline are the preexisting conditions for intensive cooling following the typhoon passage.

Measurements of Kuroshio Current velocity at the entrance to Luzon Strait along 18.75 N were made with an array of six moorings during June 2012 to June 2013. Strong positive relative vorticity of the order of the planetary vorticity f was observed on the western flank of the Kuroshio in the upper 150 m. On the eastern flank, the negative vorticity observed was about an order of magnitude smaller than f. Kuroshio transport near its origin is computed from direct measurements for the first time. Kuroshio transport has an annual mean of 15 Sv with a standard deviation of 3 Sv. It is modulated strongly by impinging westward propagating eddies, which are identified by an improved eddy detection method and tracked back to the interior ocean. Eight Kuroshio transport anomalies >5 Sv are identified; seven are explained by the westward propagating eddies. Cyclonic (anticyclonic) eddies decrease (increase) the zonal sea level anomaly (SLA) slope and reduce (enhance) Kuroshio transport. Large transport anomalies of >10 Sv within O(10 days) are associated with the pairs of cyclonic and anticyclonic eddies. The observed Kuroshio transport was strongly correlated with the SLA slope (correlation 5 0.9). Analysis of SLA slope data at the entrance to Luzon Strait over the period 1992-2013 reveals a seasonal cycle with a positive anomaly (i.e., an enhanced Kuroshio transport) in winter and spring and a negative anomaly in summer and fall. Eddy induced vorticity near the Kuroshio has a similar seasonal cycle, suggesting that seasonal variation of the Kuroshio transport near its origin is modulated by the seasonal variation of the impinging mesoscale eddies.