Atmospheric Transport to the Gaw Regional Station

A study on the connection between the state of the atmosphere, as represented by cluster-mean trajectories, and the chemical composition of precipitation at the Croatian GAW regional station of Zail,art is presented. The trajectory cluster analysis has been done on the basis ofdaily backward trajectories calculated for 1996, using the IIYSPLIT_4 trajectory model. The seasonal cluster analysis indicates four major flow directions in the region: 1) fast W-NW flow, 2) strong SW flow, 3) N-NE flow, 4) very short trajectories of different directions. The major transport route that brings higher levels of acidifiiing compounds to the region, is from the NW wind sector. The most polluted precipitation has been observed in spring with precipitation connected with three cluster me€ms: NNW, sE and E. I{ey words: pollution, air trajectories, cluster analyses SaZetak U raduje prikazana analiza veze izmedu stanja atmosfere, reprezentiranog prosjednim putaqjama, i kemijskog sastava oborine na GAW postaji Zavii,an. Klasterska arrilita puta4ja desti zraka nadinjenaje na osnovi dnelrrih putanja unatrag proradunatih za lgg6. godinu kori5tenjem modela IIYSPLIT-4. Sezonska klasterska a;nalizapokazuje detiri osnovna smjera strujanja na promatranom podrudju: a) brzo W-NW struja4je, 2) jako SW strujanje, 3) N-NE strujanje, 4) wlo kratke putanje razliditih smjerova. Osnovni smjer priienosa onedi5ie4ia koji je praien poveianim kolidinama komponenti onedi5ienja oborine na promatrano podrudje jest sa NW. Oborina s najveiom kolidinom onedi5iujuiih elemenata zabiljeZena je u proljeie i povezana s tri smjera putanja: NNW, SE i E. Kljuine rijeii: onedl!:ienje, putanje desti zraka, klasterska analiza ment, research, and a variety of other applications. To study the origin and airlsea exchange of pollutants, it is very important to understand the transport pathways of atmospheric pollutants. A number of methods have evolved to evaluate the transport ofpollutants from their source to deposition regions. Complex Eulerian and Lagrangian models are being deveIoped to describe, not only transport itself, but also the chemical processes that take place en route. However, the most common method is still the computation of a single back-trajectory to associate the upwind sourHrvatski meteorolo5ki dasopis, 35/36, 2000/01. ce region with the interpretation of chemical measurements at a given point. There are frequently clear links between the state of the atmosphere, as represented by different weather patterns, and the composition of precipitation (Smith and Hunt, 1978; Fowler and Cape, 1984; Davies et al., L984; Davies et al., !990). The purpose of this paper is to find such links for the GAW and EMEP station atZaiLan in Croatiaby analyzingthe relationship between daily precipitation chemistry data and cluster-mean trajectories. The clustered trajectories indicate possible sources of pollutant emission and the distribution of weather patterns.