Influences of vertical transport and scavenging on aerosol particle surface area and radon decay product concentrations at the Jungfraujoch (3454 m above sea level)

Concentrations of the aerosol particle surface area (SA) and aerosol-attach ed radon decay products Pb-214 and Pb-212 have been measured by means of an aerosol and a radon epiphaniometer at the Jungfraujoch research station (J FJ; 3454 m above sea level, Switzerland). These parameters exhibit a pronou nced seasonal cycle with minimum values in winter and maximum values in sum mer. In summer, pronounced diurnal variations with a maximum at 1800 LST al e often present. Highest concentrations and most pronounced diurnal variati ons occur during anticyclonic weather conditions in summer. Thermally drive n vertical transport over alpine topography is responsible for this observa tion, During this synoptic condition, concentrations vary greatly with the 500 hPa wind direction, exhibiting low concentrations for NW-N winds and hi gh concentrations for weak or S-SW winds. Lead-214 and SA are highly correl ated during anticyclonic conditions, indicating transport equivalence of th e gaseous Pb-214 precursor, Rn-222, and of aerosol particles. When cyclonic lifting is the dominant vertical transport, wet scavenging of aerosol part icles can explain the weak correlation of (214)pb and SA This conclusion is corroborated by the Pb-214/S-A ratio, being twice as high during cyclonic than during anticyclonic conditions. Lead-212 is a tracer for the influence of surface contact on a local scale due to its short lifetime of 15.35 hou rs. The analysis of this parameter suggests that high-alpine surfaces Flay an important role in thermally driven transport to the JFJ.