How to build a reduced chemical scheme for 2D/3D photochemical models?

One major step in the development of 2D/3D photochemical models and GCMs is to determine a chemical scheme that is both simple (i.e. it contains a small number of compounds and reactions) and valid (i.e. the results of the model are in agreement with a reference model). In the present paper, we present a methodology to build a reduced chemical scheme adapted to the study of hydrocarbons in the atmospheres of giant planets and Titan [1]. As an example, we have built a reduced chemical scheme containing only 25 compounds and 46 reactions (including photolysis), which is well adapted to compute the abundance of the main hydrocarbons observed so far in the atmosphere of Saturn. This scheme gives similar results, within the error bars of the model, as a 1D photochemical model using an initial chemical scheme containing 90 compounds and more than 600 reactions