Wolfgang Steinbrecht

Correlations between tropopause height and total ozone: Implications for long‐term changes

For the central European station of Hohenpeissenberg, averaging of ozone profiles grouped by tropopause height shows that the ozone mixing ratio profile in the lower stratosphere shifts up and down with the tropopause. The shift is largest near the tropopause and becomes negligible above 20 to 25 km. As a consequence a high tropopause is correlated with low total ozone and a low tropopause with high total ozone. Independent of season, total ozone decreases by 16 Dobson units (DU) per kilometer increase in tropopause height. At Hohenpeissenberg the tropopause has moved up by 150±70 m (2 σ) per decade over the last 30 years. If the −16 DU per kilometer correlation between total ozone and tropopause height is valid on the timescale of years, it is speculated that the observed increase in tropopause height could explain about 25% of the observed −10 DU per decade decrease of total ozone. This is of the same magnitude as the 30% fraction of midlatitude ozone depletion which current stratospheric models have difficulty accounting for. For Hohenpeissenberg the increase in tropopause height appears to be correlated with observed tropospheric warming: At 5 km altitude, for example, temperature has increased by 0.7±0.3 K per decade (2 σ) since 1967.

Ozone and temperature trends in the upper stratosphere at five stations of the Network for the Detection of Atmospheric Composition Change

Upper stratospheric ozone anomalies from the satellite-borne Solar Backscatter Ultra-Violet (SBUV), Stratospheric Aerosol and Gas Experiment II (SAGE II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments agree within 5% or better with ground-based data from lidars and microwave radiometers at five stations of the Network for the Detection of Atmospheric Composition Change (NDACC), from 45°S to 48°N. From 1979 until the late 1990s, all available data show a clear decline of ozone near 40 km, by 10%–15%. This decline has not continued in the last 10 years. At some sites, ozone at 40 km appears to have increased since 2000, consistent with the beginning decline of stratospheric chlorine. The phaseout of chlorofluorocarbons after the International Montreal Protocol in 1987 has been successful, and is now showing positive effects on ozone in the upper stratosphere. Temperature anomalies near 40 km altitude from European Centre for Medium Range Weather Forecast reanalyses (ERA-40), from National Centers for Environmental Prediction (NCEP) operational analyses, and from HALOE and lidar measurements show good consistency at the five stations, within about 3 K. Since about 1985, upper stratospheric temperatures have been fluctuating around a constant level at all five NDACC stations. This non-decline of upper stratospheric temperatures is a significant change from the more or less linear cooling of the upper stratosphere up until the mid-1990s, reported in previous trend assessments. It is also at odds with the almost linear 1 K per decade cooling simulated over the entire 1979–2010 period by chemistry–climate models (CCMs). The same CCM simulations, however, track the historical ozone anomalies quite well, including the change of ozone tendency in the late 1990s.

Ozone differential absorption lidar algorithm intercomparison

An intercomparison of ozone differential absorption lidar algorithms was performed in 1996 within the framework of the Network for the Detection of Stratospheric Changes (NDSC) lidar working group. The objective of this research was mainly to test the differentiating techniques used by the various lidar teams involved in the NDSC for the calculation of the ozone number density from the lidar signals. The exercise consisted of processing synthetic lidar signals computed from simple Rayleigh scattering and three initial ozone profiles. Two of these profiles contained perturbations in the low and the high stratosphere to test the vertical resolution of the various algorithms. For the unperturbed profiles the results of the simulations show the correct behavior of the lidar processing methods in the low and the middle stratosphere with biases of less than 1% with respect to the initial profile to as high as 30 km in most cases. In the upper stratosphere, significant biases reaching 10% at 45 km for most of the algorithms are obtained. This bias is due to the decrease in the signal-to-noise ratio with altitude, which makes it necessary to increase the number of points of the derivative low-pass filter used for data processing. As a consequence the response of the various retrieval algorithms to perturbations in the ozone profile is much better in the lower stratosphere than in the higher range. These results show the necessity of limiting the vertical smoothing in the ozone lidar retrieval algorithm and questions the ability of current lidar systems to detect long-term ozone trends above 40 km. Otherwise the simulations show in general a correct estimation of the ozone profile random error and, as shown by the tests involving the perturbed ozone profiles, some inconsistency in the estimation of the vertical resolution among the lidar teams involved in this experiment.

Pressure and Temperature Differences between Vaisala RS80 and RS92 Radiosonde Systems

Abstract In several twin flight campaigns, Vaisala RS80 radiosonde systems report lower temperatures than Vaisala RS92 systems in the daytime. Simultaneous differences increase from less than 0.1 K at pressure altitudes below 100 hPa to 0.7 K at 10 hPa. Much of the difference can be explained by an overcorrection of the RS80 radiation error. At night, RS92 and RS80 sounding systems report very similar simultaneous temperatures throughout the atmosphere. Geopotential heights from RS92 pressure, temperature, and humidity data (pTU heights) are within 25 m of geopotential heights from the RS92 global positioning system data (GPS heights) from the ground up to about 70 hPa. At higher altitudes, RS92 sondes produced after July 2004 show nearly identical pTU and GPS heights, but other manufacturing batches show systematic differences, up to ±100 m near 10 hPa. RS80 sondes provide much less accurate pressure and geopotential height. On average, they give up to 1 hPa higher pressure and 20 m lower pTU heights tha...

Interannual changes of total ozone and northern hemisphere circulation patterns

Linear regression accounting for the quasi-biennial oscillation, the 11-year solar cycle, stratospheric volcanic aerosol loading, and a long-term trend, accounts for 53% of the interannual ozone variance observed in February at Hohenpeissenberg (48°N, 11°E). When tropospheric circulation patterns are added to the regression, a substantially larger fraction (81%) of the observed total ozone variance can be described. The Polar Eurasia circulation pattern, negative anomalies of tropospheric geopotential height over Greenland and Arctic Canada coupled to opposite anomalies over Central Europe and North-Eastern China, is essential in accounting for interannual variations of February total ozone at Hohenpeissenberg. A large part (≈ 25%) of the February long-term ozone decline at Hohenpeissenberg appears to be related to a more frequent positive phase of this pattern. Circulation could influence ozone directly through transport, or indirectly enhance Arctic chemical ozone depletion through cold temperatures. Since climate change in the northern hemisphere winter manifests itself in a pattern very similar to the Polar Eurasia pattern, this study gives a strong indication that climate change might affect the stratospheric ozone layer.

Detecting recovery of the stratospheric ozone layer

As a result of the 1987 Montreal Protocol and its amendments, the atmospheric loading of anthropogenic ozone-depleting substances is decreasing. Accordingly, the stratospheric ozone layer is expected to recover. However, short data records and atmospheric variability confound the search for early signs of recovery, and climate change is masking ozone recovery from ozone-depleting substances in some regions and will increasingly affect the extent of recovery. Here we discuss the nature and timescales of ozone recovery, and explore the extent to which it can be currently detected in different atmospheric regions.

Quasi 2 day waves in the summer mesosphere: Triple structure of amplitudes and long‐term development

Upper mesosphere OH temperature measurements are compared at the stations of Wuppertal (51 degrees N, 7 degrees E) and Hohenpeissenberg (48 degrees N, 11 degrees E) for 2004-2009 in order to form a combined data set which considerably improves the measurement statistics. This allows time analyses near the Nyquist frequency (2 days) which is used for a study of the quasi 2 day wave (QTDW) in summer. The well-known maximum near solstice is observed. In addition, there are two unexpected side maxima about 45-60 days before and after the center peak. A similar triplet is seen in the QTDW analysis of Microwave Limb Sounder temperature data. The triple structure is also found in a very similar form 15 years earlier in the interval 1988-1993 in early Wuppertal data. In these 15 years the time distance between the first and last triple peak has increased by about 22 days. Amplitudes of the QTDW correspond to the meridional gradient of the quasi-geostrophic potential vorticity (from MLS data) and baroclinic instabilities (bc) from radar winds (at Juliusruh, 55 degrees N, 13 degrees E). Parameter bc also shows a triple structure, when mean values 2003-2008 are calculated. The QTDW triplet results from the combination of atmospheric (in) stability and critical wind speed. The widening of the QTDW triple structure suggests a long-term change of mesospheric stability and wind structure. This is found, indeed, in the bc and zonal wind data. The changes likely reflect a long-term circulation change in the middle atmosphere extending up to the mesopause.

Seasonal oscillations of middle atmosphere temperature observed by Rayleigh lidars and their comparisons with TIMED/SABER observations

The long-term temperature data sets obtained by Rayleigh lidars at six different locations from low to high latitudes within the Network for the Detection of Atmospheric Composition Change (NDACC) were used to derive the annual oscillations (AO) and semiannual oscillations (SAO) of middle atmosphere temperature: Reunion Island (21.8°S); Mauna Loa Observatory, Hawaii (19.5°N); Table Mountain Facility, California (34.4°N); Observatoire de Haute Provence, France (43.9°N); Hohenpeissenberg, Germany (47.8°N); Sondre Stromfjord, Greenland (67.0°N). The results were compared with those derived from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite

New evidence for ozone depletion in the upper stratosphere

Differential absorption lidar measurements at the Meteorological Observatory Hohenpeisenberg between 1987 and 1993 show a statistically significant ozone decrease between 32 and 42 km, peaking at about −1.7% per year at 39 km altitude. This depletion is higher than reported by SAGE II or SBUV, yet the Hohenpeisenberg data agree very well with the results from Umkehr measurements. The observed ozone trend is in the upper range of predictions from photochemical models (−0.5 to −1.5% per year), whereas SBUV and SAGE II results are close to the lower end of the simulations. The agreement with photochemical models indicates that the depletion is most likely caused by catalytic ozone destruction through anthropogenic chlorine.

Results of the 1998 Ny‐Ålesund Ozone Monitoring Intercomparison

The Ny-Alesund Ozone Monitoring Intercomparison (NAOMI) took place at Ny-Alesund,Spitsbergen (78.92 degrees N, 11.95 degrees E), from January 20 to February 10, 1998.This paper focuses on comparing stratospheric ozone profiles measured by the Alfred WegenerInstitute differential absorption lidar (AWI DIAL), in routine Network for Detection ofStratospheric Change (NDSC) operation at Ny-Alesund, the mobile Goddard Space Flight CenterDIAL (GSFC DIAL), the University of Bremen microwave radiometer (mu Wave), andelectrochemical concentration cell (ECC) ozonesondes, flown routinely by AWI. Below 30 km thetwo DIALs and the ECC sondes give virtually the same results, with instrumental precision(repeatability) better than +/-5% and no detectable bias. When their coarser altitude resolution isnot accounted for, the mu Wave data show 15% low bias at 16 km and 15% high bias at 23 km,Considerably better agreement, better than +/-5% around 20 km and above 30 km, is found whenthe altitude resolution of the other data is degraded to match that of the mu Wave. During NAOMIthe mu Wave data show high bias of up to 10% in a mixing ratio plateau around 25 km. Such biashas not been seen in routine intercomparisons between mu Wave and ECC sonde data atNy-Alesund. It is likely caused by an a priori profile 40% higher than the true profile duringNAOMI, Above 30 km the mu Wave data show the best precision (repeatability), about +/-3 to+/-5%. Precision of the GSFC DIAL data decreases from better than +/-5% at 30 km to about+/-10% at 40 km, and the precision for the AWI DIAL data decreases from better than +/-5% at30 km to +/-30% at 40 km. From 34 to 38 km the AWI profile is 12% lower than the GSFCprofile. AWI DIAL measurements that are low at 35 km often end below 40 km of show highvalues at 40 or 45 km, This behavior seems related to the way in which the AWI processingalgorithm changes altitude resolution for data with poor signal-to-noise ratio.