Three-year observations of halocarbons at the Nepal Climate Observatory at Pyramid (NCO-P, 5079 m a.s.l.) on the Himalayan range
1University of Urbino, Institute of Chemical Sciences, Urbino, Italy
2University of Urbino, Dept. of Physics, Urbino, Italy
3CNR-Institute for Atmospheric Sciences and Climate, Bologna, Italy
4Laboratoire de Glaciologie et Géophysique de l'Environnement, Université Grenoble 1-CNRS, Grenoble, France
5Ev-K2-CNR Committee, Bergamo, Italy
6CINFAI, National Consortium of Universities for Atmospheric and Hydrospheric Physics, Italy
Abstract. A monitoring programme for halogenated climate-altering gases has been established in the frame of the SHARE EV-K2-CNR project at the Nepal Climate Laboratory – Pyramid in the Himalayan range at the altitude of 5079 m a.s.l. The site is very well located to provide important insights on changes in atmospheric composition in a region that is of great significance for emissions of both anthropogenic and biogenic halogenated compounds. Measurements are performed since March 2006, with grab samples collected on a weekly basis. The first three years of data have been analysed. After the identification of the atmospheric background values for fourteen halocarbons, the frequency of occurrence of pollution events have been compared with the same kind of analysis for data collected at other global background stations. The comparison with time series from other stations has also allowed to derive Meridional gradients, which are absent for long living well mixed species, while for the more reactive species, the gradient increases inversely with respect to their atmospheric lifetime. The effect of long range transport and of local events on the atmospheric composition at the station has been analysed as well, allowing the identification of relevant source regions the Northern half of the Indian sub-continent. Also, at finer spatial scales, a smaller, local contribution of forest fires from the Khumbu valley has been detected.