Distribution files for am version 12.2, a software tool for optical depth, radiative transfer, and refraction computations involving propagation through the atmosphere and other media at microwave through submillimeter wavelengths. Application areas include radio astronomy, atmospheric spectral radiometry, and radio spectrum management. am-12.2.tgz - gzipped tar archive containing the source code and Makefile for Unix, Linux, and macOS installations. am-12.2-x64.zip - zip archive containing Windows installer and readme files. Both archives include the am cookbook, a collection of application example files. The program is made available under the following license: This computer program containing an atmospheric propagation model for the submillimeter band is a work of the United States and may be used freely, with attribution and credit to the Smithsonian Astrophysical Observatory. The program is intended for educational, scholarly or research purposes. In connection with any commercial use of the program, the user should disclose clearly and conspicuously all of the information contained in the first sentence of this notice.