Atmospheric Physics and Chemistry
The state of the Earth’s global climate system is the result of the balance between radiation absorbed from the Sun and that emitted by the planet, and governed by the properties of the surface and atmospheric constituents. AOS research in atmospheric physics is focused on understanding the intricate nature of the radiative, convective, microphysical and dynamical processes together with their interactions in the surface-atmosphere system, and how they govern the thermal state and hydrological cycle of the planet on different space and time scales.
AOS researchers use a hierarchy of numerical models of varying complexity to address these objectives, drawing on a variety of satellite and other observations to aid in physical interpretations. The cycle of water substance (vapor, liquid and ice) in the atmosphere, involving convection, aerosols, cloud physics, radiation and precipitation, constitutes a central research challenge, both in the understanding of present-day phenomena and how this water cycling may change with global warming. Human-induced and natural perturbations (e.g., carbon dioxide, ozone and aerosols, land-use; volcanic eruptions, changes in Sun’s output) lead to a radiative forcing of the climate system. State-of-the-art climate models are used to investigate the resulting global- and regional-scale changes from pre-industrial times to the present and into the 21st century.
AOS research in atmospheric chemistry consists of investigations of the composition of the natural and polluted atmospheres using numerical models of atmospheric circulation and fundamental knowledge of chemistry, together with meteorological and chemical observations. Chemistry-convection-transport models are used by AOS researchers in investigations of environmental issues ranging from acid deposition to changes in atmospheric levels of pollutants and climate forcing agents such as aerosols, tropospheric ozone and methane. Depletion of stratospheric ozone and its recovery in the 21st century, along with past and future changes in stratospheric climate, constitute another important chemistry-climate problem.
AOS researchers are developing modeling tools to address simultaneously the role of human influence upon atmospheric composition and the effect of composition on climate. Ongoing research includes coupling atmospheric models to ocean and land models to study the global biogeochemical cycles of nitrogen, carbon, and sulfur.