One-dimensional model describing aerosol formation and evolution in the stratosphere: I. Physical processes and mathematical analogs

We have developed a time-dependent one-dimensional model of the stratospheric sulfate aerosol layer. In constructing the model, we have incorporated a wide range of basic physical and chemical processes in order to avoid predetermining or biasing the model predictions. The simulation, which extends to an altitude of 58 km, includes the troposphere as a source of gases and condensation nuclei and as a sink for aerosol droplets; however, tropospheric aerosol physics and chemistry are not fully analyzed. The size distribution of aerosol particles is resolved into 25 discrete size categories from 0.01--2.56 μm. In the model, sulfur gases reaching the stratosphere are oxidized by a series of photochemical reactions into sulfuric acid vapor. At certain heights this reslts in a supersaturated H2SO4--H2O gas mixture with the consequent deposition of aqueous sulfuric acid solution on the surfaces of condensation nuclei. The newly formed droplets grow by heteromolecular heterogeneous condensation of acid and water vapors; the droplets also undergo Brownian coagulation, settle under the influence of gravity and diffuse in the vertical direction. Below the tropopause, particles are washed from the air by rainfall