Abstract: Using in-situ data collected by summer cruises during 2021—2023, summer hydrological variations and their relationship with meteorological elements were studied. The results show that summer temperature and salinity were charactered by northeast-southwest distribution pattern, while variations in values were significant during the investigation. Mean sea surface temperature (SST) was lowest in 2021 but highest in 2022. Bottom temperature was highest in 2021, but moderate in 2022 and lowest in 2023. Strong runoff extended diluted waters to more seaward and cover wider areas, SSS (sea surface salinity) was strikingly lower in 2022 than those in 2021 and 2023. Bottom salinity was highest in 2023, moderate in 2021 and lower in 2022. Temperature and salinity variations in the middle and low layers were related to the passage of typhoon and invasion of shelf cold and saline water. Bottom shelf water intruded into Lingding Bay, forming a low-temperature zone and apparent salinity front. Those vertical temperature and salinity observed after Typhoon Lupit passed in 2021 mixed homogeneously, and stratification was weakened. Middle and bottom temperature (salinity) decreased (increased) owing to enhanced bottom shelf water intrusion in sequence in 2022 and 2023. Vertical onshore winds can transport bottom shelf water shoreward to decrease temperature and increase salinity. The positive correlation between SST and air temperature suggested that SST varied with air temperature.

Key words: Pearl River Estuary, hydrology, spatiotemporal variations, shelf water, onshore wind