Steady-state modelling of hydroxyl radical concentrations at Mace Head during the EASE ’97 campaign, May 1997

Two different steady-state methods are applied to calculate OH radical concentrations based on the rates of known source and sink processes. The first method, which calculates only OH radical concentrations from measured data including HO2 gives good correlation with measured OH concentrations but overpredicts by 30%. The second method applied calculates OH, HO2 and RO2 radical concentrations simultaneously. This second method overestimates the measured concentrations of OH by almost 3 times. This apparent overprediction may be a result of calculated concentrations of HO2 which appear too high and may be indicative of a gap in our understanding of the relevant peroxy radical chemistry or a result of the limited peroxy radical chemistry assumed by the method.