Abstract:
Evaporation ducting is the dominant mechanism affecting the detection performance of marine radar systems. The inhomogeneity and abrupt changes of the evaporation ducts caused by sea surface temperature (SST) front remain an important research topic. During the Air-Sea Interaction Survey (ASIS) in the spring of 2018, the observation vessel passed through the Kuroshio SST front twice and obtained precious observational data. Based on these data and combined with the European Centre for Medium-Range Weather Forecasts reanalysis data (ERA-Interim) and the Hybrid Single Particle Lagrangian Integrated Trajectories (HYSPLIT), two important periods are distinguished and highlighted. The S1 segment, which lasted for 21 h, was dominated by a stable condition with air flowing from warmer water to colder water. During this period, the airflow passed from the warmer Kuroshio water area to the colder shelf water area, leading to a marine inner boundary layer with strong temperature inversion and the formation of sea fog. Meanwhile, the evaporation duct height (EDH) suddenly dropped to zero. The S2 segment lasted for almost 66 h and was dominated by a near neutral to slightly unstable condition with the air flowing from the colder water area to the warmer water area and the model-derived EDH was about 12 m. Numerical simulations show that during the simulation period, the inhomogeneity and abrupt changes of the EDH over the Kuroshio SST front maintained, and the abrupt changes were more robust over areas where warmer water flowed to colder water. This enhanced synoptic forcing of the Kuroshio SST front on the evaporation ducts is related to abrupt stratification change and sea fog formation.