Since its original release in 1997 (version 1.0), the code has been widely used in air quality and global aerosol modeling studies. As a result, it is regularly updated and expanded. It’s most recent extension, known as ISORROPIA II, incorporate a larger number of aerosol species (Ca, Mg, K salts) and was developed with support from NOAA. ISORROPIA-II is designed to be a superset of ISORROPIA, and uses the exact same routines as ISORROPIA to compute the equilibrium composition when crustal species are not present (i.e., when concentration of Ca, K, Mg are zero). This means that replacing ISORROPIA with ISORROPIA-II should produce identical results, except when crustal species are present.
ISORROPIA has been phased out and replaced by ISORROPIA-II. Updates to the source code of ISORROPIA 1.7 were discontinued June 1, 2010 (although the source code and manual for 1.7 are available for download), but support will be provided for ISORROPIA-II.
Users of ISORROPIA are encouraged to download ISORROPIA-II, which can be found on Code Repository, at their earliest convenience. Those that have chosen not to update the source code to ISORROPIA-II will still continue to recieve support (as routines of 1.7 are incorporated in ISORROPIA-II) but will have to manually maintain their copy.
A code (called HETV) which is based on the algorithms of ISORROPIA for sulfate, nitrate and ammonium aerosol systems has been developed. This code is optimized for running on vectorized architectures.