Parameterised chemistry

Methane destruction in the stratosphere was first parameterised according to 2-D model calculations by C. Bruehl (1993). These methane loss rates were later replaced by RIVM 2-D model loss rate factors relative to OH loss rates. The methane loss due to reaction with OH in TM is multiplied with a factor equal to the ratio of the loss by reactions with OH, Cl and O1D to the loss by OH only in the RIVM 2-D model. The multiplicative factors are always larger of equal to 1. They are read in from file ch4rds.d, and calculated by program ch4relds (called from script non_annual) from the RIVM 2-D model loss rates in input file ch4des_rivm2d.d.
The RIVM loss rates are diurnal (daily mean?) values on the mid-days of each month (day 15, 46, 74, 105, 135, 166, 196, 227, 258, 288, 319 and 349) in cm-3s-1 at 17 levels and 19 latitudes. Besides methane is nudged towards observations at 10 hPa, see the section on boundary conditions of methane above.
Note that this parameterisation assumes that the OH concentration in TM is correct in the stratosphere, which is somewhat doubtful. While in the previous formulation based on Bruehl the loss due to reactions with OH, Cl and O1D was scaled to 40 Tg/yr, this is no longer the case in the new parameterisation. How much is it actually ?