THE ASAD ATMOSPHERIC CHEMISTRY INTEGRATION PACKAGE AND CHEMICAL-REACTION DATABASE

The ASAD software package frees the atmospheric chemist from writing c ode to solve chemical time dependent equations and can be used for a w ide range of problems including stratospheric chemistry, tropospheric chemistry or pollution studies, and for 1D, 2D and 3D models. Since li ttle programming is required, the effects of programming errors are gr eatly reduced and consistent results between different models ensured. Through the use of input files to list the desired chemical species a nd their properties and the chemical reactions, different chemical sce narios can be rapidly developed and tested without any additional prog ramming. ASAD comprises a plug-in subroutine library to solve atmosphe ric chemistry time-dependent problems, a chemical reaction database an d utility programs. ASAD has been designed to be coupled to any type o f atmospheric model and be used as far as possible as a 'black box'. T he code has been carefully optimized for performance and it will vecto rize well on machines with this capability. It includes a choice of in tegrators based on published methods and supports approximations often used in atmospheric chemistry modelling, such as chemical families, f ractional products and the steady state approximation. ASAD also suppo rts the inclusion of user-supplied schemes for wet and dry deposition, source emissions, heterogeneous chemistry and photolysis. (C) 1997 El sevier Science B.V.