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Formation of nitric acid/water ice particles in cirrus clouds
Author(s) -
Kärcher B.,
Voigt C.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl025927
Subject(s) - cirrus , ice crystals , nitric acid , dissolution , ice cloud , aerosol , adsorption , clear ice , materials science , chemical physics , atmospheric sciences , analytical chemistry (journal) , mineralogy , environmental chemistry , chemistry , arctic ice pack , geology , sea ice , meteorology , inorganic chemistry , radiative transfer , climatology , physics , antarctic sea ice , optics , organic chemistry
Nitric acid (HNO 3 ) in cirrus ice crystals has been measured in the last decade during airborne field campaigns at latitudes 53°S–68°N. The HNO 3 content in ice crystals, expressed in terms of HNO 3 /H 2 O molar ratio, and the fraction of HNO 3 in ice derived from those measurements exhibit a clear upward trend with decreasing temperature. The observations are explained by a novel model describing dissolution of HNO 3 in liquid aerosol particles serving as freezing nuclei and subsequent trapping of HNO 3 during ice crystal growth. The efficiency of trapping increases with decreasing temperature. Efficient trapping occurs via diffusional burial of the ambient HNO 3 below about 203 K, because of long residence times of HNO 3 molecules at the ice surface. This opens the possibility for HNO 3 ‐induced modifications of processes affecting ice crystal growth. At warmer temperatures, molecular processes in the ice surface layer cause an increasingly rapid escape of adsorbed HNO 3 into the gas phase and render trapping less efficient despite faster ice growth rates.