Atmospheric science faculty candidate to give seminar April 3 Ronald Calhoun, an atmospheric science faculty candidate, will present a seminar, “Combined Sensor and Modeling Approaches for Environmental Flows” at 3:30 p.m. Tuesday, April 3, in 134 Ryan Hall. The trend toward increasing population in urban areas, as seen, for example, in the growth of the number of “mega cities,” creates new opportunities for social and commercial interaction, but also new and unique vulnerabilities. The management or solution of some of these challenges, such as those associated with air pollution, depends upon an improved understanding of the mechanisms of exposure and their fluid mechanical underpinnings. Innovations in sensor technology and computational modeling increasingly allow an intermingling of the two approaches. Recent advances in remote sensing of atmospheric flows and corresponding efforts to build optimal interpretations of the data will be explored. Current atmospheric measurement campaigns and applications from catastrophe management, biosolid disposal, and human health will be discussed. Remote sensing technology and computational processing, as well as unique aspects of ASU's coherent Doppler lidar system will be described. A range of numerical algorithms to interpret or assimilate data from modern sensors will be discussed. For example, velocity vectors have been educed from single and dual scanned planes of lidar data during the Joint Urban Dispersion Experiment (JU2003). Several ongoing collaborations for the assimilation of data using 4DVAR (four-dimensional data assimilation) will be presented. The efficacy of methods to retrieve dissipation of turbulent kinetic energy will be analyzed - with emphasis on appropriate satisfaction of underlying assumptions from classical turbulence theory. -- Karen Ryba, director of communications, aerospace, ryba@aero.und.edu, 777-4761