Short description of model

ISORROPIA is a model that calculates the composition and phase state of an ammonia-sulfate-nitrate-chloride-sodium-water inorganic aerosol in thermodynamic equilibrium with gas phase precursors. The code was originally developed at the Division of Marine and Atmospheric Chemistry of the Rosenstiel School of Marine and Atmospheric Science, University of Miami. The objectives were to develop a computationally efficienct and rigorous aerosol thermodynamics module for usage in regional and global aerosol models. The complete theory of ISORROPIA, together with a detailed description of the equations solved, the activity coefficient calculation methods and the computational algorithms used can be found in Nenes et al., 1998a,b. The performance and advantages of ISORROPIA over the usage of other thermodynamic equilibrium codes has been assessed in numerous studies (e.g., Nenes et al. 1998b; Ansari and Pandis, 1999ab; Yu et al., 2005). It has been evaluated wth numerous in-situ data sets (e.g., Nowak et al., in press; Yu et al., 2005).

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 constantly being updated and expanded (the most current public release is version 1.7). Currently it is being extended to incorporate a larger number of aerosol species (Ca, Mg, K and carbonates); this will be known as ISORROPIA II and is being developed with support from NOAA.

ISORROPIA can solve for two classes of problems:

Forward (or "closed system") problems, in which known quantities are temperature, relative humidity and the total (i.e. gas+aerosol) concentrations of NH3, H2SO4, Na, HCl and HNO3. Such computations are needed when the total concentrations of precursors are solved for in a model.

Reverse (or "open system") problems, in which known quantities are temperature, relative humidity and the aerosol phase concentrations of NH3, H2SO4, Na, HCl and HNO3. Such computations are needed in detailed models of aerosol dynamics, such as MADM (Pilinis et al.,2000 ).

In both types of problems, the aerosol can be either in a thermodynamically stable state (where salts precipitate once the aqueous phase becomes saturated) or in a metastable state (where the aerosol is composed only of a supersaturated aqueous phase).

The source code of ISORROPIA is written primarily in FORTRAN 77. The only extensions to the ANSI standard implemented were the usage of INCLUDE statements, trailing comments, and variable names with length larger than 6 characters (but not larger than 9). These extensions are supported by the majority of FORTRAN 77 compilers, and are also included in the Fortran 90 standard, so they should not pose any portability problems. The model has extensively been tested on many platforms (DEC Alpha, HP and IBM RISC workstations under UNIX, Intel-based PC’s under MS-DOS and Windows 95) and compilers (both FORTRAN 77 and Fortran 90). The results during these tests were found to be independent of the system used.

Recently, 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.

User support

For questions or to report bugs, please send an e-mail to either Athanasios Nenes (nenes@eas.gatech.edu) or Christos Fountoukis (Christos.Fountoukis@chbe.gatech.edu). When reporting bugs, please provide the specific input (i.e. precursor concentrations, T, RH) together with the output generated from the code, the computer platform and compiler options used. If relevant, provide the line of the code where the error was generated.

ISORROPIA mail list

Subscribe to the mail list to obtain updates and announcments about revisions to the code. To subscribe, just send an e-mail to nenes@eas.gatech.edu.

Download the latest version of the code (version 1.7)

Notice: By downloading these codes, you agree to abide with these terms of usage. If you do not agree to any of these terms, you may not download the codes.

Stand-alone executable (ISO1_7Bin.zip) that runs under Windows 9x/NT/2000/ME/XP (Last updated: January 18, 2007)

Source code (e-mail nenes@eas.gatech.edu to request the password) (Last updated: January 18, 2007)

ISORROPIA manual (Last updated: March 15, 2006).

Acknowledgments

The development of the first release of the code (version 1.0) was done with support from the Environmental Protection Agency under grant R-824793010, from the National Science Foundation under grant ATM-9625718, and from the ONR studentship by grant N000149510807.

Versions 1.1 to 1.6 were developed with the contributions of many people. In particular we would like to acknowledge the contributions (in alphabetical order): Asif Ansari, Veronique Bouchet, Prakash Bhave, Bill Hutzel, Kevin Kapaldo, Bonyoung Koo, Sonia Kreidenweis, Paul Makar, Federico San Martini, Chris Nolte, Betty Pun, Armistad Russell, Uma Shankar, Jason West, Douglas Waldron, Ashraf Zakey, Yang Zhang. The feedback and bug reports from many other individuals using the code is greatly appreciated.

Version 1.7 was developed with support from the National Oceanic and Atmospheric Administration (NOAA) under contract NMRAC000-5-04017. We would also like to acknowledge the contributions of Prakash Bhave and Chris Nolte.

References

Ansari AS, Pandis SN (1999a) An analysis of four models predicting the partitioning of semivolatile inorganic aerosol components, Aeros.Sci.Tech., 31, 129-153

Ansari AS, Pandis SN (1999b) Prediction of multicomponent inorganic atmospheric aerosol behavior, Atmos.Env., 33, 745-757

Makar, P.A., Bouchet, V.S., and Nenes, A. (2003) Inorganic Chemistry Calculations using HETV – A Vectorized Solver for the SO4-NO3-NH4 System Based on the ISORROPIA Algorithms, Atmos.Env., 37, 2279-2294, (Journal reprint) Note

Nenes A, Pandis SN, Pilinis C (1998a). ISORROPIA: A new thermodynamic equilibrium model for multiphase multicomponent inorganic aerosols, Aquat.Geoch., 4, 123-152 (Preprint, Journal reprint) Note

Nenes A., Pilinis C., and Pandis S.N. (1998b) Continued Development and Testing of a New Thermodynamic Aerosol Module for Urban and Regional Air Quality Models, Atmos. Env., 33, 1553-1560 (Journal reprint) Note

J.B. Nowak, L.G. Huey, A.G. Russell, J. A. Neuman, D. Orsini, S.J. Sjostedt, A.P. Sullivan, D.J. Tanner, R.J. Weber, A. Nenes, E. Edgerton, and F.C. Fehsenfeld, Analysis of Urban Gas-phase Ammonia Measurements from the 2002 Atlanta Aerosol Nucleation and Real-time Characterization Experiment (ANARChE), J.Geoph.Res., accepted for publication. (Preprint, Journal reprint) Note

Pilinis, C., Capaldo, K.P., Nenes, A., Pandis, S.N. (2000) MADM - A New Multicomponent Aerosol Dynamics Model, Aerosol Sci. Tech., 32(5), 482-502 (Journal reprint) Note

Yu, S.,Dennis, R., Roselle, S., Nenes, A., Walker, J.T., Eder, B., Schere, K., Swall, J. and Robarge, W. (2005) An assessment of the ability of 3-D air quality models with current thermodynamic equilibrium models to predict aerosol NO3-. J.Geoph.Res.,110, D07S13, doi:10.1029/2004JD004718, 2005 (Preprint, Journal reprint) Note