The background levels of the summer tropospheric aerosol and trace gases in Greenland

Abstract

A description is given of airborne measurements over Greenland of the concentration of Aitken nuclei and large (optical) particles, and of the concentration of ice nuclei. Measurements on the surface of the concentration of Aitken nuclei and large particles and concentrations of various chlorocarbons are also reported. The synoptic meteorology of the period is described and used to elucidate the results. The particle concentrations aloft were generally log-normally distributed over rather narrow ranges around geometric mean values of 312 cm −3 for Aitken nuclei and 3.50 cm −3 for large particles. These concentrations are considerably lower and much less variable than found in earlier years and possible reasons for that are discussed. The particle concentrations over the ice cap were generally lower than over the surrounding ocean and that is in agreement with previous results. Ice nuclei concentrations were generally lower than 0.11 −1 and high values were connected with incursions of frontal air. Particle concentrations at the surface were found to be very similar to those aloft, in contrast to findings in earlier years. Trace gas concentrations were similar to those measured in other background areas. On several occasions the aerosol was found to have reached a steady state with respect to coagulation, nucleation and transport and the results have accordingly been used to estimate nucleation rates in and mass transport fluxes to the Greenland atmosphere.