Aerosols and chemistry in the planetary atmospheres

Abstract

This dissertation is devoted to studying aerosols and their roles in regulating chemistry, radiation, and dynamics of planetary atmospheres. In chapter I, we provided a fundamental mathematical basis for the quasi-equilibrium growth assumption, a well-accepted approach to representing formation of secondary organic aerosols (SOAs) in microphysical simulations in the Earth’s atmosphere. Our analytical work not only explains the quasi-equilibrium growth, which emerges as a limiting case in our theory, but also predicts the other types of condensational growth, confirmed by the recent laboratory and field experiments. In chapter II, we presented a new photochemical mechanism in which the evaporation of the aerosols composed of sulfuric acid or polysulfur on the nightside of Venus could provide a sulfur source above 90 km. Our model results imply the enhancements of sulfur oxides such as SO, SO2, and SO3. This is inconsistent with the previous model results but in agreement with the recent ground-based and spacecraft observations. In chapters III and IV, we developed a nonlinear optimization approach to retrieve the aerosol and cloud structure on Jupiter from the visible and ultraviolet images acquired by the Cassini spacecraft, combined with the ground-based near-infrared observations. We produced the first realistic spatial distribution of Jovian stratospheric aerosols in latitudes and altitudes. We also retrieved the stratospheric temperature and hydrocarbon species based on the mid-infrared spectra from the Cassini and Voyager spacecrafts. Based on the above information, the accurate and detailed maps of the instantaneous radiative forcing in Jovian stratosphere are obtained, revealing a significant heating effect from the polar dark aerosols in the high latitude region and therefore a strong modulation on the global meridional circulation in the stratosphere of Jupiter. In chapter V, we study the transport of passive tracers, such as aerosols, acetylene (C2H2) and ethane (C2H6) in the Jovian stratosphere, using both analytical and numerical approaches. We established several benchmark analytical solutions for the coupled photochemical-advective-diffusive system to understand its basic behaviors under different assumptions. A numerical two-dimensional chemical transport model is applied to Jupiter, and the effects of eddy mixing process and meridional circulation on the distributions of stratospheric species are discussed.