General Theory of Radiative Processes

Abstract

This chapter focuses on the microscopic physical processes responsible for the emission and absorption of radiation. The opening section describes some basic properties of the Planck function and related physical principles, followed by detailed discussions of the theoretical background behind the atmospheric gas and condensate spectra. The microwave gas spectrum is constituted of a limited number of absorption lines owing to molecular oxygen and water vapor transitions, while the infrared gas spectrum is a full of absorption lines primarily from vibrational transitions of water vapor and carbon dioxide molecules. Water condensates give rise to their own spectral features distinct from the gaseous counterpart. The chapter offers an introductory course to outline the physical basis of those radiative properties of atmospheric constituents.