Recent studies have demonstrated a link between ozone changes caused by human activities and changing UV levels at the Earth's surface, as well as a link to climate through changes in radiative forcing and links to changes in chemical composition. This book draws together key scientists who provide state of the art contributions on the variable ozone layer and the interplay of longwave and shortwave radiative interactions which link ozone, the climate and UV issues.

Following the rapid developments in the UV-B measurement techniques and the rapidly growing research in the field in the late 80's and early 90's, we organized a large gathering of distinguished experts in a NATO Advanced Study Institute, held in Halkidiki, Greece on October, 2-11. 1995. The Institute was organized so as to include state of the art lectures on most aspects of solar ultraviolet radiation and its effects. This was achieved by extended lectures and discussions given in five sessions by 27 lecturers and a demonstration of filed measurements and calibration techniques at the end of the Institute. The ASI began with the sun and fundamentals on solar radiative emissions and their variability in time and continued with the interaction of solar Ultraviolet with the atmosphere through the complex scattering processes and photochemical reactions involved. Particular emphasis was given to changes in atmospheric composition imposed by different manifestations of the solar activity cycle. as well as on the modelling of radiative transfer through the atmosphere and the ocean under variable environmental conditions. Overviews on the ozone issue. its monitoring and variability were extensively discussed with emphasis on the observed acceleration of ozone decline in the early 90's. This acceleration had as a consequence, significant increases in UV-B radiation observed at a few world-wide distributed stations.

This volume contains progress papers in atmospheric ozone research which were presen- ted at the Ouadrennial Ozone symposium held in Greece from 3 to 7 September, 1984. These pa- pers are grouped in nine chapters corresponding to the nine sessions of the symposium. The Editors proVide the following summary of the highlights for each chapter; this summary has been prepared after consulting the papers submitted for publication as well as session summa- ries kindly provided by the following session chairmen: R. Bojkov, H. DOtsch, P. Fabian, J. Hai- gh, I. Isaksen, L. Kaplan, K. KOnzi, J. London, H. Mantis, C. Mateer, A. Matthews, G. Megie and J. Russell. Chapter 1 entitled: Chemical -radiative -dynamical model calculations includes results from recent developments in modeling techniques. The chapter begins with the results from a two -dimensional model using isentropic coordinates. With prescribed diabatic heating rates and a judicious choice of eddy diffusion coefficients this method can produce realistic fields of several stratospheric species. Three dimensional model simulations come next which demon- strate ozone transport by the stationary and transient components of the flow and emphasize the role of wave transport of ozone during a sudden stratospheric warming. The problem of chemical model validation is addressed in several different approaches.

Recent studies have demonstrated a link between ozone changes caused by human activities and changing UV levels at the Earth's surface, as well as a link to climate through changes in radiative forcing and links to changes in chemical composition. This book draws together key scientists who provide state of the art contributions on the variable ozone layer and the interplay of longwave and shortwave radiative interactions which link ozone, the climate and UV issues.