This volume contains refereed papers submitted by international experts who participated in the Atmospheric Modeling workshop March 15 -19, 2000 at the Institute for Mathematics and Its Applications (IMA) at the University of Minnesota. The papers cover a wide range of topics presented in the workshop. In particular, mathematical topics include a performance comparison of operator-splitting and non- splitting methods, time-stepping methods to preserve positivity and consideration of multiple timescale issues in the modeling of atmospheric chemistry, a fully 3D adaptive-grid method, impact of rid resolution on model predictions, testing the robustness of different flow fields, modeling and numerical methods in four-dimensional variational data assimilation, and parallel computing. Modeling topics include the development of an efficient self-contained global circulation-chemistry-transport model and its applications, the development of a modal aerosol model, and the modeling of the emissions and chemistry of monoterpenes that lead to the formation of secondary organic aerosols. The volume provides an excellent cross section of current research activities in atmospheric modeling.