Distribution of precipitation and wet deposition around an island mountain in south-west Poland

A comparison has been made between measurements of precipitation intensity and chemical composition and a three-dimensional model of airflow and orographic rainfall enhancement. The 'seeder-feeder' effect is shown to be of importance in rainfall distribution, wet deposition of pollutants and the modification of the chemical composition of rainfall over an isolated island mountain. The results show increases in rainfall of between 30% and 83% over the hill, with the smallest increase corresponding to the presence of a strong inversion layer. The peak rainfall enhancement occurred between 0.5 and 2 lan downstream of the summit. The measured concentrations of major ions in the feeder-cloud droplets were greater than those in seeder rain by factors of between two and five. The scavenging of polluted cap cloud by rain drops resulted in an increase in wet-deposition rate by factors of between three and five, with the peak deposition occurring approximately 2 lan downstream of the hill summit.