Exploring atmospheric boundary layer characteristics in a severe SO2 episode in the north-eastern Adriatic 1Andrija Mohorovičić Geophysical Institute, Department of Geophysics, Faculty of Science, University of Zagreb, Croatia
2Meteorological and Hydrological Service of Croatia, Zagreb, Croatia
3Laboratory of Geoinformatics and Environmental Application, Department of Marine Sciences, University of the Aegean, 81100 Mytilene, Greece
Received: 23 December 2008 – Published in Atmos. Chem. Phys. Discuss.: 09 March 2009 Abstract. Stable atmospheric conditions are often connected with the occurrence of
high pollution episodes especially in urban or industrial areas. In this
work we investigate a severe SO2 episode observed on 3–5 February 2002
in a coastal industrial town of Rijeka, Croatia, where very high daily mean
concentrations (up to 353.5 μg m−3) were measured. The episode
occurred under high air pressure conditions, which were accompanied with a
fog and low wind speeds. Three air quality models (50-km EMEP model, 10-km
EMEP4HR model and 1-km CAMx model) were used to simulate SO2
concentrations fields and to evaluate the relative contribution of distant
and local pollution sources to observed concentrations. Results suggest that
the episode was caused predominately by local sources. Furthermore, using
three-dimensional, higher-order turbulence closure mesoscale meteorological
model (WRF), the wind regimes and thermo-dynamical structure of the lower
troposphere above the greater Rijeka area (GRA) were examined in detail.
Modelled atmospheric fields suggest several factors whose simultaneous
acting was responsible for elevated SO2 concentrations. Established
small scale wind directions supported the transport of air from nearby
industrial areas with major pollution sources towards Rijeka. This transport
was associated with strong, ground-based temperature inversion and
correspondingly, very low mixing layer (at most up to about 140 m).
Additionally, the surface winds in Rijeka were light or almost calm thus,
preventing ventilation of polluted air. Finally, a vertical circulation cell
formed between the mainland and a nearby island, supported the air
subsidence and the increase of static stability.
Revised: 01 July 2009 – Accepted: 06 July 2009 – Published: 13 July 2009
Citation: Prtenjak, M. T., Jeričević, A., Kraljević, L., Bulić, I. H., Nitis, T., and Klaić, Z. B.: Exploring atmospheric boundary layer characteristics in a severe SO2 episode in the north-eastern Adriatic, Atmos. Chem. Phys., 9, 4467-4483, doi:10.5194/acp-9-4467-2009, 2009.