The use of spectral analysis to examine model and observed O3 data

A study of the possible use of spectral analysis techniques to compare model results and observed data was made. The power spectrum for the model results and observed data, as well as the cross-amplitude, absolute coherency and phase spectrum, were calculated at 12 sites across eastern North America for hourly O3 data for the period between 15 July 1988 and 30 September 1988. It was found that the spectral technique is very useful in pointing out similarities and differences between the model results and observed data for time scales such as the trend, day-to-day variation and diurnal cycle. In the present paper, the techniques used are presented in some detail. We also give some indications how to interpret the results. Only the results for Brookings, South Dakota, are described in detail as an illustration of the use of the technique.