Observations, Modeling, and Laboratory Studies
(Blake, Hoffmann, Okumura, Salawitch, Sander,
Yung, Wennberg, Webster)

The processes responsible for the controlling the distribution of ozone in the stratosphere are being actively studied by a number of scientists at Caltech and JPL. Stratospheric ozone shields the Earth's surface from the majority of solar ultraviolet light that enters the atmosphere. During the last few decades, however, the concentration of ozone has declined significantly leading to more efficient transmission of this harmful radiation. The release of chlorofluorocarbons (CFCs) has significantly altered the chemistry of the stratosphere and the increased chlorine abundance is implicated in the decline of ozone.

    Laboratory studies of the fundamental spectroscopy and photo-physics of many of the trace gases present in the stratosphere are being performed by Profs. Blake, Okumura, Wennberg, and Dr. Sander. The rates of chemical reactions occurring in both the aerosol and gas phases are being studied by Prof. Hoffmann and Dr. Sander. Dr. Salawitch and Prof. Yung have developed a number of photochemical and coupled chemistry-dynamics models of the stratosphere that serve to integrate the laboratory measurements and provide a means to compare theory with atmospheric observations. Measurements of trace gases in the stratosphere are being performed from the ground by Dr. Sander, and from aircraft by Prof. Wennberg and Dr. Webster. These observations are being obtained with a new generation of instruments deployed on numerous aircraft, balloon and ground campaigns throughout the year at locations including Alaska, Hawaii, Brazil, and New Zealand. Measurements of radicals, reservoirs, and tracers are used to study stratospheric ozone photochemistry and to quantify the role of stratosphere-troposphere exchange in atmospheric circulation.