Patrick Hamill¹, Colette Brogniez², Christine David³ and Larry Thomason⁴

¹Physics Department, San Jose State University, San Jose, California, USA
²Laboratoire d'Optique Atmospherique, Universite des Sciences et Technologies de Lille, France
³CNRS Service Aeronomie, Université Pierre et Marie Curie, Paris, France
⁴NASA Langley Research Center, Hampton, Virginia, USA

SPARC (Stratospheric Processes and their Role in Climate) is carrying out a Stratospheric Aerosol Climatology which will be primarily based on satellite observations of the aerosol layer, but with significant input from other measurement systems, primarily balloon borne optical particle counters and lidar systems. We are collecting data from numerous lidar systems throughout the world and using lidar profiles along with satellite extinction measurements to obtain as complete a picture as possible of the stratospheric aerosol as a function of latitude, altitude and time. We shall discuss the results from various lidar systems and present intercomparisons where possible. Further, we shall evaluate the agreement between lidar and satellite measurements. A fundamental consideration is the transformation of the backscatter measured by lidar systems to the extinction measured by satellite sensors. This is especially important after the eruptions of highly energetic volcanoes. Satellite borne instruments such as SAGE and HALOE cannot make extinction measurements in the lower stratosphere under conditions of heavy aerosol loadings. Lidar measurements are essential for formulating an aerosol climatology that is valid for post-volcanic periods. One of the goals of the SPARC climatology is to generate a set of "standard stratospheric aerosol models" which will give modelers values of various aerosol properties (such as surface area, composition, etc.) as a function of latitude, season and volcanic condition of the stratosphere.