A simple analytical model of aerosol properties with account for hygroscopic growth 1. Equilibrium size spectra and cloud condensation nuclei activity spectra

A microphysical model of aerosol size spectra that includes hygroscopic growth is presented. In the presence of atmospheric humidity, an aerosol size spectrum of the Junge [1952] type transforms into a superposition of two equilibrium power law spectra, with indices determined by the original Junge index and the fraction of soluble material contained in the aerosol. The aerosol size distributions are presented as explicit functions of relative humidity H for three different humidity regimes: (1) moderate humidity, (2) high humidity but subsatturation, and (3) interstitial cloud aerosol. On the basis of this model of aerosol hygroscopic growth, the Twomey [1959] cloud condensation nuclei (CCN) power law is then derived so that its coefficients are related to the aerosol microstructure and humidity dependence under subsaturation. This simple aerosol model can be used in cloud and climate models that do not treat explicitly CCN activation and for evaluation of aerosol optical properties. An application for aerosol optical properties is considered by Khvorostyanov and Curry [this issue].

[1]  J. Curry,et al.  A simple analytical model of aerosol properties with account for hygroscopic growth: 2. Scattering and absorption coefficients , 1999 .

[2]  P. Hobbs,et al.  Measurements of aerosol optical properties in marine air , 1996 .

[3]  V. Khvorostyanov.  Mesoscale processes of cloud formation, cloud-radiation interaction, and their modelling with explicit cloud microphysics , 1995 .

[4]  P. Hobbs,et al.  Cloud condensation nuclei over the Arctic Ocean in early spring , 1995 .

[5]  J. Curry,et al.  Water vapor feedback over the Arctic Ocean , 1995 .

[6]  B. Stevens,et al.  An explicit cloud microphysics/LES model designed to simulate the Twomey effect , 1994 .

[7]  D. Tanré,et al.  Effect of variations in super-saturation on the formation of cloud condensation nuclei , 1994, Nature.

[8]  J. Coakley,et al.  Climate Forcing by Anthropogenic Aerosols , 1992, Science.

[9]  D. Hegg,et al.  Heterogeneous production of cloud condensation nuclei in the marine atmosphere , 1990 .

[10]  J. W. Fitzgerald,et al.  The Size and Scattering Coefficient of Urban Aerosol Particles at Washington, DC as a Function of Relative Humidity. , 1982 .

[11]  J. W. Fitzgerald.  Approximation Formulas for the Equilibrium Size of an Aerosol Particle as a Function of Its Dry Size and Composition and the Ambient Relative Humidity , 1975 .

[12]  Gottfried Hänel,et al.  Computation of the extinction of visible radiation by atmospheric aerosol particles as a function of the relative humidity, based upon measured properties , 1972 .

[13]  F. Kasten.  Visibility forecast in the phase of pre-condensation , 1969 .

[14]  S. Twomey,et al.  The nuclei of natural cloud formation part II: The supersaturation in natural clouds and the variation of cloud droplet concentration , 1959 .

[15]  W. Mordy.  Computations of the Growth by Condensation of a Population of Cloud Droplets , 1959 .

[16]  J. Curry.  Interactions among Turbulence, Radiation and Microphysics in Arctic Stratus Clouds , 1986 .

[17]  J. Hudson.  Cloud Condensation Nuclei Measurements Within Clouds. , 1984 .

[18]  Á. Mészáros,et al.  On the concentration and size distribution of atmospheric sulfate particles under rural conditions , 1978 .