A THEORETICAL AND OBSERVATIONAL INVESTIGATION OF THE RESPONSE OF OZONE TO SHORT-TERM VARIATIONS IN THE SOLAR ULTRAVIOLET IRRADIANCE

An analysis of the response of middle atmospheric ozone to short-term variations in the solar ultraviolet irradiance is presented. Measurements of ozone from the Solar Mesosphere Explorer (SME) ultraviolet spectrometer (UVS) are compared to the calculations of a one-dimensional, radiative-photochemical model of the upper stratosphere and lower mesosphere. The model uses temporally varying solar UV irradiances measured by the SME solar spectrometer.; Measurements made by the SME UVS in the 0.1 to 1 mb range show evidence that tropical ozone responds to solar rotational variation when analyzed using both frequency and time domain techniques. Three periods during 1982 and 1983 were selected for the analysis. The solar irradiance during each period exhibited different spectral characteristics. A significant 27-day variation in the solar irradiance at 205 nm was measured during mid-1982 with an amplitude of 2.5 percent. Observations of ozone near the stratopause during this period showed a corresponding variation with a 1.3 percent amplitude. Analysis of ozone variations at extratropical latitudes revealed different periodicities that were not correlated with solar variations.; Calculations of the amplitude and phase of the ozone response due to solar UV oscillations made by the model show that the effects of the coupling of radiation and photochemistry in the region near the stratopause may not be neglected. The maximum temperature variation at 0.75 mb over a solar rotation is computed as no greater than 0.6 K. This variation will damp the amplitude of the response of ozone to the solar UV variations by 25 percent.; The amplitude of the measured response is, in all cases, systematically larger than the theoretical calculations but is, nonetheless, in agreement when the uncertainties in the analysis are considered. Temperature feedback can account for, at most, a 1.5-day phase lead of ozone with respect to the solar UV variations. This is in sharp disagreement with the observations which show 5- to 7-day phase leads during two of the periods studied. Possible explanations for this discrepancy are discussed.