Abstract
Almost all cloud droplets are formed by heterogeneous nucleation, i. e., by condensation ofthe atmospheric water vapor onto hygroscopic aerosol particles as (NH4) 2SO4 called cloud condensationnuclei (CCN). During cloud droplet formation, (NH4) 2SO4 dissolves to break up into ions in condensedwater. On the other hand, atmospheric gases as CO2 (g) are absorbed concurrently. Dissolution of CCN andabsorption of CO2 (g) may interact each other through aqueous chemical reactions and, therefore, theresultant acidity of cloud droplets are different from those caused by CCN and CO2 (g) separately. In orderto investigate the interactive effects on cloud droplet acidity a mathematical model has been constructedand made some numerical simulations. Calculations show that, at low temperature (less than about 10degree Celsius), the higher the CCN concentration, the lower the cloud droplet acidity becomes. Thismeans CCN acts as a buffer with CO2 (g) acidification at low temperature.
