Above the surface, the CO mixing ratio is set at 10 ppb prior to spin-up. Corresponding values for PAN and acetone are based on model results by Wang et al. Initial isoprene mixing ratios, on the other hand, are based on sparse observations summarized by Houweling et al. Sources of reactive chlorine and bromine other than methyl chloroform are assumed to be in steady state. The surface value of methyl chloroform is initially set at 100 ppt below 10S and 140 ppt above 30N, varying linearly in between.
Methyl chloroform is absent in the free atmosphere prior to spin-up.
Each model year consists of 360 days, with 30 days allotted to each month .