Ground-based radiometers are currently operated in research labs around the globe and are also used as routine measurement tools for water vapor and temperature profiling. This reference provides a comprehensive picture of ground-based radiometry, starting with the basic principles. It provides information on ground-based instrumentation, retrieval techniques, and temperature structure. It also covers temperature profiling and water vapor radiometry. In addition, it provides retrieval algorithms using MATLAB®, worked examples of derived products, and polar atmosphere cases.