Open AccessQuantifying wet scavenging processes in aircraft observations of nitric acid and cloud condensation nuclei
Author(s) -
Garrett T. J.,
Avey L.,
Palmer P. I.,
Stohl A.,
Neuman J. A.,
Brock C. A.,
Ryerson T. B.,
Holloway J. S.
Publication year - 2006
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006jd007416
Subject(s) - scavenging , cloud condensation nuclei , nitric acid , aerosol , precipitation , atmospheric chemistry , environmental chemistry , environmental science , relative humidity , cloud base , atmospheric sciences , chemistry , meteorology , ozone , cloud computing , geology , inorganic chemistry , physics , organic chemistry , computer science , antioxidant , operating system , biochemistry
Wet scavenging is an important sink term for many atmospheric constituents. However, production of precipitation in clouds is poorly understood, and pollutant removal through wet scavenging is difficult to separate from removal through dry scavenging, atmospheric mixing, or chemical transformations. Here we use airborne data from the International Consortium for Atmospheric Research on Transport and Transformation project to show that measured ratios of soluble and insoluble trace gases provide a useful indicator for quantifying wet scavenging. Specifically, nitric acid (HNO 3 ), produced as a by‐product of combustion, is highly soluble and removed efficiently from clouds by rain. Regional carbon monoxide (CO), which is also an indicator of anthropogenic activity, is insoluble and has a lifetime against oxidation of about a month. We find that relative concentrations of HNO 3 to regional CO observed in clear air are negatively correlated with precipitation production rates in nearby cloudy air ( r 2 = 0.85). Also, we show that relative concentrations of HNO 3 and CO can be used to quantify cloud condensation nucleus (CCN) scavenging by precipitating clouds. This is because CCN and HNO 3 molecules are both fully soluble in cloud water and hence can be treated as analogous species insofar as wet scavenging is concerned. While approximate, the practical advantage of this approach to scavenging studies is that it requires only measurement in clear air and no a priori knowledge of the cloud or aerosol properties involved.