Lagrangian particle dispersion (HYSPLIT) model analysis of the sea breeze case with extreme mean daily PM10 concentration in Split, Croatia.

The case of a sea breeze where the mean daily PM10 concentration reached the recommended limit value for human health for the period from 2007 to 2009 at the air quality station AMS3 Split-1 in Split, Croatia, is analysed. The Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) atmospheric model MM5 and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model are used to simulate the lower atmospheric flow and dispersion within 100 km from the coast. The simulation is made with four point sources in the hinterland of Split: Kaštel-Sućurac, Solin and Klis, where the local cement plants are located, and Vranjic, where an asbestos-cement plant is located. Statistical analysis and rotational statistics showed good agreement of the measurement data with the modelled wind speed and direction at 10 m and temperature at 2 m height. The backward trajectories show that the pollutants are caught in the sea breeze circulation from all sources and in the early afternoon the plume is placed over parts of Split from all sources. From the peak concentrations during the selected day, it can be concluded that pollution from Kaštel-Sućurac had the greatest impact on the high PM10 concentrations measured at the Split-1 station.