A climatology of the diurnal variations in stratospheric and mesospheric ozone over Bern, Switzerland

Abstract

Abstract. The ground-based radiometer GROMOS, stationed in Bern (47.95 • N, 7.44 • E), Switzerland, has a unique data set: it obtains ozone profiles from November 1994 to present with a time resolution of 30 min and equivalent quality during night-and daytime. Here, we derive a monthly climatology of the daily ozone cycle from 17 years of GRO-MOS observation. We present the diurnal ozone variation of the stratosphere and mesosphere. Characterizing the diurnal cycle of stratospheric ozone is important for correct trend estimates of the ozone layer derived from satellite observations. The diurnal ozone cycle from GROMOS is compared to two models: the Whole Atmosphere Community Climate Model (WACCM) and the Hamburg Model of Neutral and Ionized Atmosphere (HAMMONIA). Generally, observation and models show a good agreement: in the lower mesosphere, daytime ozone is for both GROMOS and models around 25 % less than midnight ozone. In the stratosphere, ozone reaches its maximum in the afternoon showing values several percent larger than the midnight value. Further, GROMOS and models indicate a seasonal behaviour of the diurnal ozone variations in the stratosphere with a larger afternoon maximum during daytime in summer than in winter. Using the 17 years of ozone profiles from GROMOS, we find strong interannual variations in the diurnal ozone cycle for both the stratosphere and the mesosphere. Interannual variability in temperature, atmospheric circulation and composition may explain the observed interannual variability of the diurnal ozone cycle above Bern.

Daily ozone cycle in the stratosphere: global, regional and seasonal behaviour modelled with the Whole Atmosphere Community Climate Model

“…Thus, it seems that WACCM should be quite reliable with regard to information about the daily ozone cycle at any region. In addition, we find the daily ozone cycle of WACCM in good agreement with observations by a microwave radiometer at Bern, Switzerland (Studer et al, 2014), which operates as part of the frame of NDACC and with satellite-based observations of SMILES (Sakazaki et al, 2013) and TIMED or SABER (Huang et al, 2008). The surprising strong daily ozone cycle at high latitudes in polar summer is confirmed by observations of a ground-based microwave radiometer at Ny-Ålesund, Svalbard (Palm et al, 2013).…”

“…A similar increase of ozone during the afternoon was found in a climatology of the daily ozone cycle observed by the ground-based microwave radiometer GROMOS in Bern, Switzerland (Studer et al, 2014). Satellite-based observations from SMILES (Kikuchi et al, 2013), SABER and MLS showed a morning minimum and a late-afternoon maximum in the daily ozone cycle in the tropics and subtropics (Huang et al, 2008;Sakazaki et al, 2013).…”

“…Previous simulation studies were focused on northern midlatitudes (Pallister and Tuck, 1983). Observational studies (Kikuchi et al, 2013) presented the daily ozone cycle of the tropics and midlatitudes or local data (Studer et al, 2014). Figure 6 gives a complete view of the seasonal change of D O 3 as function of day of year (DOY) and geographic latitude as simulated by WACCM.…”

“…Haefele et al (2008) found a daily ozone cycle in the observations of the Ground-based Millimeter-wave Ozone Spectrometer (GROMOS) which operates at Bern, Switzerland as part of Network for the Detection of Atmospheric Composition Change (NDACC). Later, Studer et al (2014) derived a monthly climatology of diurnal variation in stratospheric and mesospheric ozone from 17 years of GROMOS observations. Satellite-based observations from SMILES (Superconducting Submillimeter-Wave Limb-Emission Sounder) (Kikuchi et al, 2013), SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) (Russell et al, 1999) and MLS (Microwave Limb Sounder) (Barth et al, 1983) showed the existence of a daily ozone cycle in the stratosphere at tropical and midlatitudes (Huang et al, 2008;Sakazaki et al, 2013).…”

An updated version of a gap-free monthly mean zonal mean ozone database

“…As a results, diurnal variations in ozone concentrations are observable in the upper stratosphere and lower mesosphere . Therefore, differences in ozone concentrations measured in the upper stratosphere-lower mesosphere could result from satellitebased instruments measuring ozone at a different solar zenith angles, i.e., different local time of the day (e.g., Pallister and Tuck, 1983;Schanz et al, 2014;Studer et al, 2014). With the current version of BSVertOzone, the potential differences in ozone measurements caused by the diurnal cycle are ignored as the effect on the monthly mean zonal mean ozone values is expected to be small.…”