Analysis of temperature inversion in the Zhujiang River Estuary in July 2015

Abstract

This study investigates the temperature inversion phenomenon in the Zhujiang (Pearl) River Estuary (ZRE) using hydrological data collected in a summer cruise during July 6–17, 2015. The results suggest that temperature inversion occurred primarily near the salinity front, with an average temperature difference (ΔT) of 0.42°C between the inversion layer and the underlying water. The inversion layer was approximately 4 m thick on average, with an upper boundary at a depth of 1–6 m and a lower boundary at a depth of 3–10 m. Different mechanisms and dynamic processes were responsible for temperature inversion in different parts of the study area. (1) At the salinity front in the west of the ZRE, the measurements collected by CTD (conductivity, temperature, and depth) showed that the low-salinity water mass on the inner side of the front was approximately 2°C cooler than the high-salinity water mass on the outer side. Temperature inversion occurred when the cooler low-salinity water overlapped the warmer high-salinity water near the front due to the driving force of the background flow. (2) Inversion layers occurred at the mouth of the Taiping waterway as a result of varying horizontal flow between two different water masses under the effects of tides and runoff. (3) To the southwest of Hong Kong, temperature inversion occurred due to the interaction of upwelling and the salinity front.