The Chemical Mechanism Integrator Cminor v1.0: A Stand-Alone Fortran Environment for the Particle-Based Simulation of Chemical Multiphase Mechanisms

Abstract. We present version 1.0 of the Chemical Mechanism Integrator (Cminor), a fully modularized modern Fortran software package for the computational simulation of skeletal and detailed chemical kinetic systems derived from atmospheric and combustion chemistry. Cminor aims for the efficient simulation of complex chemical mechanisms by using various mathematical techniques. These are tailored to systems of ordinary differential equations (ODEs), having the specific structure arising from chemical reaction systems. Additionally, a high-speed mechanism parser allows the user to interchange reactions or their parameters in an ASCII format text file and immediately start a new simulation without recompiling, enabling fast and numerous simulations. Cminor's solver technique is based on Rosenbrock methods. Different measures of local errors and an analytical Jacobian matrix approach are implemented, where efficiency is obtained by exploiting the sparsity structure of the Jacobian.

Cminor can be run in one of three configurations:

• A box-model framework for either pure gas-phase mechanisms or a multi-modal aerosol distribution dissolved in mono-dispersed cloud droplets.
• A rising adiabatic parcel, in which the activation of multi-modal aerosols is represented by solving the droplet condensation equation.
• A constant volume environment, where thermodynamic properties are evaluated by polynomial functions of temperature according to the standards of the Chemkin thermodynamic data base.

The software package is evaluated by applying seven different chemical mechanisms. Three of them are from the field of air-quality modeling and three are from the area of combustion kinetics, ranging from 7 species and 10 reactions to 10,196 species and 23,098 reactions. The last mechanism describes sulfur accumulation in clouds, which is tested along with a rising parcel and condensating cloud droplets.