This comprehensive text outlines the principles underlying our current knowledge of the physics and chemistry of the lower and middle atmospheres. Written to allow a physics or chemistry major without prior knowledge of atmospheric science to enter the subject at a fairly advanced level, it includes an introduction which outlines the subject from the formation of the solar system to the state of the atmosphere at present. The thermodynamics of an atmosphere in local thermodynamic equilibrium is treated systematically, and the fundamental radiative processes of scattering and absorption are discussed in two chapters. The issue of climate change is considered in terms of simple models, and the concepts underlying atmospheric chemistry are discussed in terms of the ozone problem and three topics concerning the lower atmosphere: the oxidants, the chemistry of sulfur, and the atmospheric carbon cycle. Two final chapters discuss the physics of clouds and precipitation and many aspects of the behavior of the earth's boundary layer. Several appendices deal with climate data and background material, such as the Navier-Stokes equations. Problem sets enhance the value of each chapter. All aspects of the lower and middle atmospheres, except for large-scale dynamics, are treated in a connected account as ultimate consequences of the solar radiation falling on the planet.