The book introduces optical wave propagation in the irregular turbulent atmosphere and the relations to laser beam and LIDAR applications for both optical communication and imaging. It examines atmosphere fundamentals, structure, and content. It explains specific situations occurring in the irregular atmosphere and for specific natural phenomena that affect optical ray and laser beam propagation. It emphasizes how to use LIDAR to investigate atmospheric phenomena and predict primary parameters of the irregular turbulent atmosphere and suggests what kinds of optical devices to operate in different atmospheric situations to minimize the deleterious effects of natural atmospheric phenomena.