Analysis for Cold Water Lenses off the Jiangsu Coast Based on Observation and Simulation

Based on observation data from 1982 to 2016, the daily and monthly-averaged characteristics of cold water lenses (CWLs) off the Jiangsu coast were analyzed. Most CWLs existed in hot months (from May to September), but there were also some CWLs in cool and cold months (from October to the next April). The average radius and intensity of the monthly-averaged CWLs were 81 km and 0.6 °C respectively, and the average sea surface temperature difference between the centers of CWLs and the nearshore was 2.0 °C. The contrast between wind and CWLs shows that a southerly wind was markedly helpful for the generation of CWLs in the shelf slope, but some CWLs in the coastal shoal corresponded to strong northerly wind. In addition, the contrast between tide and daily CWLs shows that the CWLs in spring tides were slightly stronger than those in neap tides. The POM-σ-z model is used to set up the numerical model for the simulation and dynamical analysis of CWLs. The impacts of realistic river runoff, ocean currents and weather conditions have been taken into account in the dynamical analysis. Then CWLs in summer is simulated, and its dynamic mechanism driven by wind, tide, river runoff and the Taiwan Warm Current is also analyzed. The simulated results indicate that its formation and development is mainly driven by two factors. One is the strong northerly wind. The other is the vertical tidal mixing.