Comparison of the seasonal variation of the aerosol size distribution at high altitude research stations in France and Nepal

Aerosol size distributions were continuously monitored during a full year at two high altitude research stations in Europe, France (1465 m a.s.l.), and Nepal (5079 m a.s.l.). Measurements were performed using Scanning Mobility Particle Sizers specially designed to be controlled by remote login and to operate for long-term periods in adverse weather conditions. The results show that the diurnal profiles of the aerosol size distribution have a seasonal variability on both sites (Figures 1 and 2). At the puy de Dome station, we observe an increase of particle concentrations of the 50 nm size in the late morning during summer, which would be representative of a significant vertical transport from polluted air masses to the free tropospheric background concentrations. Additionally to the transport of these relatively large particles, we observe the formation of new ultrafine particles from the size of below 10 nm which are growing during the day to the 50 nm range, this all through the year. The annual variation of particle size distribution will be examined in a comparative study of the two high altitude stations. Figure 1. Mean winter (Nov-Dec-Jan) daily variation of the aerosol size distribution.