John E. Frederick Professor, Department of the Geophysical Sciences and the College. Master, Physical Sciences Collegiate Division. Associate Dean, Division of the Physical Sciences and the College. Department of the Geophysical Sciences 5734 S. Ellis Ave. HGS 505 Chicago, IL 60637 USA Phone: 773/702-3237 E-mail: frederic@uchicago.edu Publications

Current research focuses on studies of solar radiative transfer, ground-based radiation measurements, and interpretation of satellite-based data. Physical mechanisms which control ultraviolet solar radiation levels at the earth's surface are being investigated via a combination of numerical simulations and measurements. Specific topics of interest include the roles of scattering by clouds and absorption by atmospheric trace gases in shielding the biosphere from damaging solar radiation. An issue under study centers on the possibility that molecules contained in cloud droplets over industrialized regions can lead to detectable absorption of ultraviolet radiation.

Great concern exists in the Southern Hemisphere over a possible influence of the Antarctic ozone depletion on middle latitudes. In response to this, a network of ground-based ultraviolet radiation monitors has been established over the latitudinal extent of Argentina. Analysis of data obtained from Tierra del Fuego reveals periods of enhanced ultraviolet radiation levels in the weeks after the breakup of the polar "ozone hole" during some years. The largest percentage increases in biologically damaging irradiances appear in the late spring and summer months when the natural background radiation levels are already large. The extent to which such increases appear at lower latitudes, where most of the country's population resides, is still to be determined.

Finally, data to be obtained by the Total Ozone Mapping Spectrometer carried on Japan's Advanced Earth Observing Satellite will be used to study the reflecting properties of cloudy atmospheres on a global scale, but with special emphasis on locations where ground-based radiation observations are available. Radiative transfer in atmospheres which lack horizontal homogeneity is of particular interest here.

Education:

• Ph.D., University of Colorado, 1975