This book combines theoretical concepts with experimental results on thermal microwave radiation to increase the understanding of the complex nature of terrestrial media. With the emphasis on radiative transfer models, this new book covers the urgent needs for the transition from the experimental phase of microwave remote sensing to operational applications. This book covers all terrestrial aspects from clear to cloudy atmosphere, precipitation, ocean and land surfaces, vegetation, snow and ice.A chapter on new results of microwave dielectric properties of natural media, covering wavelengths from the decimetre to the submillimetre range, will be a source for further radiative transfer developments, which extends the applicability to radar and other electromagnetic tools, which include extraterrestrial objects, for example planets and comets.