Textbook in PDF format This second edition of Differential Optical Absorption Spectroscopy (DOAS) has been meticulously updated to enhance its clarity and relevance. Responding to the growing popularity of DOAS techniques, this edition expands the sections on atmospheric radiative transfer, covering new and crucial topics such as the ring effect and profile inversion techniques. Additionally, the book presents a comprehensive array of DOAS applications and techniques, ranging from research applications using imaging and satellite DOAS to emission monitoring from volcanoes and industrial facilities by LED long-path DOAS, as well as mobile MAX-DOAS and Cavity-Enhanced DOAS. The discussion of DOAS retrieval algorithms has significantly broadened to incorporate the latest developments, particularly pertinent to the satellite community