Regional effect on urban atmospheric nucleation
- 1Institute of Chemistry, Eötvös University, 1518 Budapest, P.O. Box 32, Hungary
- 2Department of Physics, 00014 University of Helsinki, Helsinki, P.O. Box 64, Finland
- 3Department of Meteorology, Eötvös University, 1518 Budapest, P.O. Box 32, Hungary
- 4MTA-PE Air Chemistry Research Group, 8201 Veszprém, P.O. Box 158, Hungary
Abstract. Secondary aerosol particle production via new particle formation (NPF) has been shown to be a major contributor to the global aerosol load. NPF has also been observed frequently in urban environments. Here, we investigate the effect of regional NPF on urban aerosol load under well-defined atmospheric conditions. The Carpathian Basin, the largest orogenic basin in Europe, represents an excellent opportunity for exploring these interactions. Based on long-term observations, we revealed that NPF seen in a central large city of the basin (Budapest) and its regional background occur in a consistent and spatially coherent way as a result of a joint atmospheric phenomenon taking place on large horizontal scales. We found that NPF events at the urban site are usually delayed by > 1 h relative to the rural site or even inhibited above a critical condensational sink level. The urban processes require higher formation rates and growth rates to be realized, by mean factors of 2 and 1.6, respectively, than the regional events. Regional- and urban-type NPF events sometimes occur jointly with multiple onsets, while they often exhibit dynamic and timing properties which are different for these two event types.