Ozone distribution in the middle latitude mesosphere as derived from microwave measurements at Lindau (51.66°N, 10.13°E)

Abstract

[1] Mesospheric ozone measurements between 50 and 80 km altitude were carried out in middle latitude at Lindau (51.66°N, 10.13°E), Germany, by means of the microwave technique between 1993 and 2006, with an interruption from 1997 to 1998. We utilize data obtained between 1998 and 2006. The measurements show a tendency of typical ozone features that occurs in each year. The most marked patterns are a late summer maximum of ozone in the middle and lower mesosphere which is shifted into autumn and winter in the stratopause region, and a distinct nighttime maximum around 72 km during the winter season, whereas no annual maximum occurs there during daytime. A clear annual asymmetry of the nighttime ozone distribution exists in this domain, marked by a decline of the mean ozone values in January/February and an increase to a subsidiary annual maximum a few kilometers higher in March/April. This asymmetry at the height of the well-known middle mesospheric maximum of ozone (MMM, often called the tertiary ozone maximum) results from the asymmetric occurrence rate of sudden stratospheric warmings (SSWs) occurring more frequently after winter solstice than before. Additionally, the asymmetric annual variation of water vapor with lowest values just around spring equinox influences the annual variation of ozone. A strong influence on the nighttime ozone concentration is the zonal wind. The night-to-day ratios (NDRs) in the middle to upper mesosphere display a distinct winter anomaly marked by values more than twice as high as in summer. The NDR is modulated by pronounced oscillations with a planetary time scale. The maximum effect occurs at 65–70 km, clearly below the height of the MMM.