Premium
A new parameterization of H 2 SO 4 /H 2 O aerosol composition: Atmospheric implications
Author(s) -
Tabazadeh Azadeh,
Toon Owen B.,
Clegg Simon L.,
Hamill Patrick
Publication year - 1997
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 - 10.1029/97gl01879
Subject(s) - sulfuric acid , aerosol , supercooling , nucleation , aqueous solution , relative humidity , water vapor , vapor pressure , stratosphere , ice nucleus , thermodynamics , vapour pressure of water , chemistry , atmospheric pressure , mineralogy , atmospheric sciences , meteorology , inorganic chemistry , geology , physics , organic chemistry
Recent results from a thermodynamic model of aqueous sulfuric acid are used to derive a new parameterization for the variation of sulfuric acid aerosol composition with temperature and relative humidity. This formulation is valid for relative humidities above 1% in the temperature range of 185 to 260 K. An expression for calculating the vapor pressure of supercooled liquid water, consistent with the sulfuric acid model, is also presented. We show that the Steele and Hamill [1981] formulation underestimates the water partial pressure over aqueous H 2 SO 4 solutions by up to 12% at low temperatures. This difference results in a corresponding underestimate of the H 2 SO 4 concentration in the aerosol by about 6% of the weight percent at approximately 190 K. In addition, the relation commonly used for estimating the vapor pressure of H 2 O over supercooled liquid water differs by up to 10% from our derived expression. The combined error can result in a 20% underestimation of water activity over a H 2 SO 4 solution droplet in the stratosphere, which has implications for the parameterization of heterogeneous reaction rates in stratospheric sulfuric acid aerosols. The influence of aerosol composition on the rate of homogeneous ice nucleation from a H 2 SO 4 solution droplet is also discussed. This parameterization can also be used for homogeneous gas phase nucleation calculations of H 2 SO 4 solution droplets under various environmental conditions such as in aircraft exhaust or in volcanic plumes.