Ozone diurnal variations in the stratosphere and lower mesosphere, based on measurements from SABER on TIMED

Abstract

We report on derived results of global zonal mean ozone diurnal variations over 24 h of local solar time, based on satellite measurements from SABER on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, with focus on the stratosphere and lower mesosphere. On a global scale, results in this altitude range are new. We had previously reported on ozone diurnal variations, but the focus was at higher altitudes, where the variations can be relatively large. In the stratosphere, there can be systematic diurnal variations on the order of a few percent, with multiple local maxima over a day, and these can exist down to altitudes of ∼31 hPa (∼24 km) and lower. At these altitudes, photochemistry is expected to be less effective, and dynamics (e.g., tides) can be more important. The diurnal variations also depend on latitude and season. As a function of altitude, for low latitudes at least, the ozone diurnal variations show a pattern of local‐time phase progression such that beginning at ∼31 hPa the mixing ratios are smaller in the afternoon (compared to values at midnight), then (as the altitude increases) become mostly larger in the afternoon beginning from ∼10 to 4.6 hPa, revert back to intermediate afternoon values near 2.2, 1.5 hPa, and again return to lower daytime values at about 1 hPa, with this last trend continuing to higher altitudes in the mesosphere. This pattern of variation is generally supported by previous results by us and by others, based on data from MLS UARS, MLS Aura, rocket‐borne, and ground‐based measurements.