MEASUREMENTS AND STEADY-STATE CALCULATIONS OF OH CONCENTRATIONS AT MAUNA-LOA-OBSERVATORY

In situ OH measurements were made as part of the spring and summer int ensives of Mauna Loa Observatory Photochemistry Experiment (MLOPEX 2). These measurements provided an opportunity to compare measured OH con centrations with those predicted by steady state models which use the many other measurements which made up MLOPEX 2 as input parameters. Th ese models thus provide a highly specific real-time view of the enviro nment in which OH was being measured. Both short- and long-term variat ions of OH are discussed along with their relation to changes in sourc es and sinks. In general, agreement between measured and modeled OH co ncentrations is good during periods when free tropospheric air masses, typically downslope, were present. During periods when certain types of upslope boundary layer air dominated the measurement site, however, measured OH concentration averaged about a factor of 2 lower than the model predictions. Possible reasons for the latter differences are su ggested, such as unidentified sinks in the boundary layer air.