Phytoplankton blooms induced by the interaction between typhoons and oceanic mesoscale eddies in the South China Sea were investigated using the composite averaging method based on cyclone‐centric coordinates from nine years (2002–2010) of satellite observations. Increases in the chlorophyll (Chl) concentration following the passage of a typhoon differed greatly among the pre‐existing cyclonic eddy (PCE), pre‐existing anticyclonic eddy (PACE) and non‐eddy (NE) ocean conditions (with Chl increases of approximately 35%, 6% and 12%, respectively), but the magnitude of sea surface temperature (SST) cooling was similar under the three conditions (∼1°C). Under the same level of SST decreases, the greater increase in the Chl concentration in the PCE condition was attributed to the longer persistence of both SST cooling and nutrient input caused by the typhoon‐strengthened PCE (associated with upwelling), which stopped the re‐warming of the typhoon‐induced cold water.

Marine phytoplankton are the basis of the whole marine ecosystem, and different groups of phytoplankton play different roles in the biogeochemical cycle. Satellite remote sensing is widely used in the retrieval of marine phytoplankton over a wide range and long time series, but not yet for taxonomical composition. In this study, we used coincident in situ measurement data from high-performance liquid chromatography (HPLC) and remote sensing reflectance (R_rs) to investigate the empirical relationships between phytoplankton groups and satellite measurements. A nonparametric model, generalized additive model (GAM), is introduced to establish inversion models of various marine phytoplankton groups. Seven inversion models (two sizes classes among the microphytoplankton and nanophytoplankton and four groups among the diatoms, dinoflagellates, chrysophytes, and cryptophytes) are applied to the South China Sea (SCS) for 2020, and satellite images of phytoplankton sizes and groups are presented. Microphytoplankton prevails in the coastal and continental shelf, and nanophytoplankton prevails in oligotrophic oceans. Among them, the dominant contribution of microphytoplankton comes from diatoms, and nanophytoplankton comes from chrysophytes. Diatoms (nearshore) and chrysophytes (outside the continental shelf) are the dominant groups in the SCS throughout the year. Dinoflagellates only become dominant in some coastal areas, while cryptophytes rarely become dominant.

The southwest monsoon between June and October induces upwelling and offshore cold‐water transport in the western South China Sea (SCS). A seasonal collocated chlorophyll bloom also occurs, resulting in a productivity increase in the oligotrophic SCS basin. To accurately quantify productivity transported toward the open ocean, it is necessary to determine whether the transport is continuous or intermittent (intraseasonal oscillation). However, intraseasonal chlorophyll oscillations during summer have not been investigated. The influences of upwelling and an eddy dipole on intraseasonal chlorophyll oscillation also remain unclear. Merged daily chlorophyll data obtained from a multisatellite ocean color product are used to investigate intraseasonal chlorophyll oscillations. Our results indicate that summer chlorophyll development is characterized by an intraseasonal double‐bloom pattern in July‐August and September‐October in 11 out of 20 years (1998–2017). The time interval between the two blooms varies between 23 and 45 days. The timing of the first bloom is correlated with upwelling (R² = 0.70), but the secondary bloom is not (R² = 0.26). During the second chlorophyll bloom period, high chlorophyll is observed in the interaction region of an eddy dipole, which is locally generated rather than transported from nearshore areas. A new index is proposed based on finite‐size Lyapunov exponents and the orientations of the associated eigenvectors to represent frontogenetic processes. The index coincides not only spatially with the chlorophyll bloom but also temporally with the chlorophyll variation during the second bloom period (R² = 0.73).

The oceanic Kármán vortex street is an important hydrokinetic phenomenon caused by the unsteady separation of sea currents in the wake of an obstacle. This study quantitatively analyzed the characteristics of the small-scale vortex street of Didicas Island in the Luzon Strait based on multimission satellite data. Five groups of vortex streets were captured, and each group was observed by two satellite images within one hour. Based on the displacement and change in the vortex street within one hour, we found that the formation time of a single vortex is longer than 40 min. The vortex propagation speed behind the island is approximately 0.98 m s⁻¹ (ranging from 0.66–1.22 m s⁻¹). The incoming velocity was calculated using the vortex propagation speed and the aspect ratio based on a vortex propagation model, which ranges from 0.72 to 1.47 m s⁻¹ The incoming speed is 1.6–2.3 times the geostrophic speed extracted from AVISO data, implying that the contribution of non-geostrophic flow to the total flow field is comparable to that of geostrophic flow in this region.

The Hong Kong-Zhuhai-Macau Bridge crosses the Pearl River Estuary and is the largest bridge and tunnel project in the world. During the construction period of this project, the excessive suspended sediment was found in the construction region. The suspended sediment generated by sand excavation in the upstream was assumed to have a significant impact on the suspended sediment in the tunnel region. In this study, we assessed the impact of upstream sand excavation on the suspended sediment in the Hong Kong-Zhuhai-Macau Bridge construction area using Landsat OLI, ETM+, and TM data. Regional suspended sediment algorithms were developed for Landsat using a symbolic regression method based on data from in situ measurements in the study area from 2003 to 2014. A band shift was conducted on the remote sensing reflectance data from Landsat ETM+ and OLI to produce a time series of the suspended sediment concentrations that was internally consistent with that of the Landsat TM data. The suspended sediment distribution was extracted and used to compare under two different conditions, with and without sand excavation. The correlations of the time series of the suspended sediment concentrations in different regions in the surrounding waters, including the correlations between the construction regions and the sand excavation regions, were calculated. Our results indicated that the sand excavation north of the Pearl River Estuary had a limited impact on the surface suspended sediment concentrations in the Hong Kong-Zhuhai-Macau Bridge tunnel area.