THE POLAR STRATOSPHERIC CLOUD EVENT OF JANUARY 24, 1989 .1. MICROPHYSICS

Rapid adiabatic cooling induced by synoptic forcing led to polar stratospheric cloud (PSC) formation on January 24, 1989, at altitudes sampled by the ER‐2 aircraft. Particle characteristics measured by the Forward Scattering Spectrometer Probe (FSSP) on the ER‐2 were compared to those calculated using a theoretical FSC microphysics model. Although calculations were sensitive to local changes in cooling rate, generally favorable agreement was found, that in particle surface area being especially important since this parameter dictates heterogeneous chemical rates. The overall model performance suggests that the current approach for simulating Type 1 (nitric acid trihydrate) PSC formation under rapid cooling conditions is well founded and can be used to study the effects of heterogeneous chemistry on stratospheric composition. Copyright 1990 by the American Geophysical Union.