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Using in situ observations collected by a drifting air-sea interface buoy (DrIB) in the northern South China Sea from August 30 to September 13, 2018, the extreme air-sea turbulent fluxes that occurred from September 8 to 13 during tropical cyclone (TC) Barijat were investigated. The most striking features were substantial increases in momentum and heat fluxes, with maximum increases of 10.8 m s-1 in the wind speed (WS), 0.73 N m-2 in the wind stress, 68.1 W m-2 in the sensible heat fluxes (SH) and 258.8 W m-2 in the latent heat fluxes (LH). The maximum WS, wind stress, SH and LH values amounted to 15.3 m s-1, 0.8 N m-2, 70.9 W m-2 and 329.9 W m-2, respectively. Using these new DrIB observations, the performance of two state-of-the-art, high-resolution reanalysis products, ERA5 and MERRA2, was assessed. The consistency of the observed values with ERA5 was slightly better than with MERRA2, reflected in higher correlations but both products underestimated the WS during TC conditions. In calm weather conditions, the turbulent heat fluxes were overestimated, because they simulated a too dry and cold atmospheric state, enhancing the air-sea differences in temperature and humidity. Considering that an accurate representation of the air-sea turbulent and momentum fluxes is essential for understanding and predicting ocean and atmospheric variability, our findings indicate that more high-quality temperature and relative humidity observations are required to evaluate and improve existing reanalysis products. [ABSTRACT FROM AUTHOR]

The Japan/East Sea (JES) is known as a mid-latitude "Miniature Ocean" that features multiscale oceanic dynamics processes. We investigate the variability of the sea surface chlorophyll-a concentration (SSC) and bloom timing in the JES based on satellite remote sensing products spanning 1998-2019. The JES SSC exhibits strong seasonal variability and blooms twice annually, which are mainly governed by the physical environmental conditions. However, the influences of local oceanic dynamic processes (e.g., upwelling, oceanic fronts, mesoscale eddies, and near-inertial oscillations) on the bloom magnitude and timing of the entire JES are not critical, compared with the PAT and stratification. In addition, significant interannual variabilities of spring bloom magnitude occur along the JES's northwestern coast, and that of fall bloom magnitude occur in the deep Japan Basin. For spring bloom, the interannual variability of the bloom timing (initiation timing, termination timing and duration), which significantly affect the interannual bloom magnitude anomalies, are correlated with climate modes such as AO and ENSO. For fall bloom, on the interannual time scale, the bloom duration is mainly affected by the initiation timing. Both of them have a significant influence on the bloom magnitude. The initiation/termination timing of spring blooms has shifted earlier by 0.37/0.45 days annually along the JES's northwestern coast; the counterpart of fall blooms has shifted 0.49/1.28 days earlier annually in the deep Japan Basin. [ABSTRACT FROM AUTHOR]

The Korea Strait (KS) is a major navigation passage linking the Japan Sea (JS) to the East China Sea and Yellow Sea. Almost all existing studies on the tides in the KS employed either data analysis or numerical modelling methods; thus, theoretical research is lacking. In this paper, we idealize the KS-JS basin as three connected uniform-depth rectangular areas and establish a theoretical model for the tides in the KS and JS using the extended Taylor method. The model-produced K1 and M2 tides are consistent with the satellite altimeter and tidal gauge observations, especially for the locations of the amphidromic points in the KS. The model solution provides the following insights into the tidal dynamics. The tidal system in each area can be decomposed into two oppositely travelling Kelvin waves and two families of Poincaré modes, with Kelvin waves dominating the tidal system. The incident Kelvin wave can be reflected at the connecting cross-section, where abrupt increases in water depth and basin width occur from the KS to JS. At the connecting cross-section, the reflected wave has a phase-lag increase relative to the incident wave by less than 180°, causing the formation of amphidromic points in the KS. The above phase-lag increase depends on the angular frequency of the wave and becomes smaller as the angular frequency decreases. This dependence explains why the K1 amphidromic point is located farther away from the connecting cross-section in comparison to the M2 amphidromic point. [ABSTRACT FROM AUTHOR]

This study focuses on different evolutions of the low-level atmospheric circulations between eastern Pacific (EP) El Niño and central Pacific-II (CP-II) El Niño. The western North Pacific anomalous anticyclone (WNPAC) originates from the northern South China Sea for EP El Niño, and moves to the western North Pacific (WNP) afterward. Compared with EP El Niño, the origin of theWNPAC is farther west during CP-II El Niño,with the center over the Indochina Peninsula.Moreover, theWNPACshows aweaker eastward shift. Such discrepancies are attributed to different evolutions of the cyclonic response over theWNP, which can suppress the convection in the western flank of the anomalous cyclone. The eastward retreat of the anomalous cyclone is significant for EP ElNiño, but less evident for CP-II El Niño. These discrepancies are related to zonal evolutions of the increased precipitation over the equatorial Pacific. Following the southwardmigration of the intertropical convergence zone (ITCZ), the deep-convection region extends eastward along the equator, reinforcing the atmospheric response to the eastern Pacificwarming inEPElNiño. ForCP-II ElNiño, the atmospheric response is insignificant over the eastern Pacific without warming. Moreover, the meridional migration of the ITCZ can modulate zonal variations of the easterly tradewind and specific humidity aswell.Due to the combined effects of the climatological background and atmospheric anomalies, the specific humidity--induced and wind-induced moist enthalpy advection contribute to different shifts of the precipitation center. [ABSTRACT FROM AUTHOR]

Seasonal variability of water properties obtained from conductivitytemperature- depth casts from 2008 to 2015 and current velocities obtained from moorings deployed from 2008 to 2009 show that the Sunda Strait plays dual roles in water exchange between the Pacific and Indian Oceans. The Sunda Strait current velocity is strongly affected by seasonal monsoon winds. During the boreal winter monsoon, northwesterly winds to the north and south of Java draw waters from the Indian Ocean into the Java Sea, and at the same time, the Java Sea receives an influx of low-salinity water from the South China Sea. Summation of these waters would reduce the main Indonesian Throughflow transport in the Makassar Strait. Conditions are reversed during the summer monsoon: higher-temperature, lower-salinity, and lower-density waters from the Java Sea are exported to the Indian Ocean through the Sunda Strait, enhancing Indonesian Throughflow transport from the Pacific into the Indian Ocean. Variations in temperature, salinity, and density are greater during the boreal summer than those observed during the winter monsoon. Kelvin-wave-like signals have been observed in the velocity time series data; however, further investigation in this region is needed to confirm the possibility of Kelvin waves entering the Sunda Strait. [ABSTRACT FROM AUTHOR]

The South China Sea (SCS) and the Java Sea (JS) are connected through the Karimata Strait, Gaspar Strait, and the southern Natuna Sea, where the tides are often used as open boundary condition for tidal simulation in the SCS or Indonesian seas. Tides, tidal currents, and tidal energy fluxes of the principle constituents K1, O1, Q1, M2, S2, and N2 at five stations in this area have been analyzed using in situ observational data. The results show that the diurnal tides are the dominant constituents in the entire study area. The constituent K1 has the largest amplitude, exceeding 50 cm, whereas the amplitudes of M2 are smaller than 5 cm at all stations. The amplitudes of S2 may exceed M2 in the Karimata and Gaspar straits. Tidal currents are mostly of rectilinear type in this area. The semi-major axes lengths of the diurnal tidal current ellipses are about 10 cm s-1, and those of the semidiurnal tidal currents are smaller than 5 cm s-1. The diurnal tidal energy flows from the SCS to the JS. The semidiurnal tidal energy flows from the SCS to the JS through the Karimata Strait and the eastern part of the southern Natuna Sea but flows in the opposite direction in the Gaspar Strait and the western part of the southern Natuna Sea. Harmonic analysis of sea level and current observation also suggest that the study area is located in the antinodal band of the diurnal tidal waves, and in the nodal band of the semidiurnal tidal waves. Comparisons show that the existing models are basically consistent with the observational results, but further improvements are necessary. [ABSTRACT FROM AUTHOR]

The existing estimates of the volume transport from the Pacific Ocean to the South China Sea are summarized, showing an annual mean westward transport, with the Taiwan Strait outflow subtracted, of 3.5±2.0 Sv (1 Sv=106 m3 s−1). Results of a global ocean circulation model show an annual mean transport of 3.9 Sv from the Pacific to the Indian Ocean through the South China Sea. The boreal winter transport is larger and exhibits a South China Sea branch of the Pacific-to-Indian Ocean throughflow, which originates from the western Philippine Sea toward the Indonesian Seas through the South China Sea, as well as through the Karimata and Mindoro Straits. The southwestward current near the continental slope of the northern South China Sea is shown to be a combination of this branch and the interior circulation gyre. This winter branch can be confirmed by trajectories of satellite-tracked drifters, which clearly show a flow from the Luzón Strait to the Karimata Strait in winter. In summer, the flow in the Karimata Strait is reversed. Numerical model results indicate that the Pacific water can enter the South China Sea and exit toward the Sulu Sea, but no observational evidence is available. The roles of the throughflow branch in the circulation, water properties and air-sea exchange of the South China Sea, and in enhancing and regulating the volume transport and reducing the heat transport of the Indonesian Throughflow, are discussed. [ABSTRACT FROM AUTHOR]