The distribution of relative humidity in cirrus clouds and its impact on the nitric acid content of Interstitial aerosol particles

摘要

Recent studies (e.g.Ovarlez et al.,2002) have shown that the relative humidities with respect to ice inside cirrus clouds (in-cloud RH_(ice)) can substantially exceed the saturation value RH_(ice)=1.0 and reach values up to RH_(ice)=1.8.A consequence of these in-cloud ice supersaturations may be a growth of the interstitial aerosol particles subsequently leading to uptake of nitric acid (HNO_3).This process could be important in the frame of the discussion on denitrification of the upper troposphere via sedimenting cirrus cloud ice particles carrying previously adsorbed HNO_3.Up to now,the mechanisms controlling the HNO_3 uptake on ice are not completely understood.In particular the amount of HNO_3 taken up by the interstitial aerosol particles -which is no longer available for adsorption on ice particles- has hitherto been neglected.