This textbook covers the essentials of atmospheric radiation at a level appropriate to advanced undergraduates and first-year graduate students. It was written specifically to be readable and technically accessible to students having no prior background in the subject area and who may or may not intend to continue with more advanced study of radiation or remote sensing. The author emphasizes physical insight, first and foremost, but backed by the essential mathematical relationships. The second edition adds new exercises, improved figures, a table of symbols, and discussions of new topics, such as the Poynting vector and the energy balance within the atmosphere. The book web page includes additional resources for courses taught using this book, including downloadable/printable PDF figures as well as solutions to most problems (for instructors of recognized courses only).