This book provides an account of stratified flows as they are relevant to the ocean and atmosphere, with a primary focus on meso-scale phenomena. The first three chapters deal with oceanic and atmospheric internal solitary waves as a significant component of the dynamics of the coastal ocean and the atmospheric boundary layer. Later chapters cover gravity currents and internal bores and turbulence in density- stratified flows, and review theoretical models for internal waves generated by flow over mountains and laboratory studies of the flow of stratified fluids past obstacles. A final chapter offers a review and tutorial of the stability theory of stratified shear flows. There is no subject index