Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

Ozone performs a key role in the middle atmosphere and its monitoring is thus necessary. At the Institute of Applied Physics of the University of Bern, Switzerland, we built a new ground-based microwave radiometer, GROMOS-C (GRound based Ozone MOnitoring System for Campaigns). It has a compact design and can be operated remotely with very little maintenance requirements, being therefore suitable for remote deployments. It has been conceived to measure the vertical distribution of ozone in the middle atmosphere, by observing pressure-broadened emission spectra at a frequency of 110.836 GHz. In addition, meridional and zonal wind profiles can be retrieved, based on the Doppler shift of the ozone line measured in the four directions of observation (north, east, south and west). In June 2014 the radiometer was installed at the Maïdo observatory, on Réunion island (21.2° S, 55.5° E). High-resolution ozone spectra were recorded continuously over 7 months. Vertical profiles of ozone have been retrieved through an optimal estimation inversion process, using the Atmospheric Radiative Transfer Simulator ARTS2 as the forward model. The validation is performed against ozone profiles from the Microwave Limb Sounder (MLS) on the Aura satellite, the ozone lidar located at the observatory and with ozone profiles from weekly radiosondes. Zonal and meridional winds retrieved from GROMOS-C data are validated against another wind radiometer located in situ, WIRA. In addition, we compare both ozone and winds with ECMWF (European Centre for Medium-Range Weather Forecasts) model data. Results show that GROMOS-C provides reliable ozone profiles between 30 and 0.02 hPa. The comparison with lidar profiles shows a very good agreement at all levels. The accordance with the MLS data set is within 5 % for pressure levels between 25 and 0.2 hPa. GROMOS-C's wind profiles are in good agreement with the observations by WIRA and with the model data, differences are below 5 m s−1 for both

VALIDATION OF GOMOS OZONE PROFILES USING NDSC LIDAR : STATISTICAL COMPARISONS

ABSTRACT The lidars deployed in the NDSC framework have been used for the validation of GOMOS onboard ENVISAT. During the commissioning phase around ten coincidences per site have been investigated. No significant bias, larger than ±5 %, has been reported except around 50 km and 20 km where both techniques are known to present some limitations. The estimated errors of both GOMOS and lidar are in good agreement with the standard deviation of the differences between coincidences. At higher latitude, comparisons are not so good because of the measurement conditions of bright limb during this period

First Ozonesonde Measurements at Kerguelen Island (49.2°S 70.1°E) Radiosondages Ozone Complementaires aux Kerguelen ROCK campaign 2008-2009 (Polar International Year - IPEV)

International audienceCommunication about First Ozonesonde Measurements at Kerguelen Island (49.2°S 70.1°E) Radiosondages Ozone Complementaires aux Kerguelen ROCK campaign 2008-2009 (Polar International Year - IPEV

Analysis of the tropospheric ozone distribution at Kerguelen island (49°S, 69°E) in 2008-2009

International audienceWe analyze a one-year campaign of 18 ozone-sondes performed at Kerguelen Island (49S, 69E), the first performed at this location. Tropospheric ozone distribution presents a large variability in summer and winter. The background level is more elevated in winter than in summer. Using correlative data from the Measurement of Pollution in the Troposphere (MODIS) instrument and the Lagrangian model FLEXPART 8.1, we show the influ- ence of the southern hemisphere biomass burning season on this seasonal variability, especially the impact of the biomass burning activity in South America and Southern Africa. A case of stratosphere-to-troposphere exchange is identified on February 2009, with an enriched ozone layer anticorrelated with water vapor. The analysis based on the ERA-INTERIM global model data and on trajectories generated by FLEXPART 8.1 evidences the influence of a stratospheric filament into the troposphere induced by a curvature of the polar jet stream, mixed with a tropospheric subtropical air mass

Twenty years of ozonesonde measurements at La Reunion Island Instrumental evolution and tropospheric ozone trends between 1992 and 2012.

International audienceSince1992 ozonesonde measurements have been performed at La Reunion Island located at 21°S and 55.5°E in the southwest Indian Ocean. In 1998, this site joined the Southern Hemisphere Additional OZonesondes (SHADOZ) program allowing to improve the frequency of measurements to once a week. Since the start of ozonesonde measurement at La Reunion Island, some instrumental changes have occurred, such as the cathode solution concentration, and the meteorological radiosonde system from Vaisala to Modem. The influence of this last modification on data has been analyzed with several dual flights. In November 2011, in collaboration with the Finnish Meteorological Institute (FMI), simultaneous measurements have been made combining the Modem, 2 types of Vaisala sondes and the Cryogenic Frost point Hygrometer (CFH). Tropospheric ozone trends have been estimated. Considering the whole tropospheric column, a positive trend has been observed. Trend calculations have also been investigated, separating the troposphere into different layers and according to seasons. The strongest trends are observed in the upper troposphere, and during austral winter. The purpose of this presentation is to describe the instrumentation, its evolution and the impact of instrumental changes, to discuss intercomparisons between different sondes and to present long-term trends characteristics

Ozonesonde measurements at La Reunion Island (21°S 55.5°E): historical evolution, instrumental discussion and tropospheric ozone trends between 1992 and 2011

International audienceCommunication about Ozonesonde measurements at La Reunion Island (21°S 55.5°E): historical evolution, instrumental discussion and tropospheric ozone trends between 1992 and 201

Mesures d'ozone par radiosondage à l'île de La Réunion (21°S 55.5°E) : évolution historique, discussion expérimentale et tendances de l'ozone troposphérique entre 1992 et 2011

National audienceCommunication about Mesures d'ozone par radiosondage à l'île de La Réunion (21°S 55.5°E) : évolution historique, discussion expérimentale et tendances de l'ozone troposphérique entre 1992 et 201

Tropospheric ozone and stratosphere-to-troposphere exchange in the Southern Indian Ocean and South Africa

International audienceCommunication about Tropospheric ozone and stratosphere-to-troposphere exchange in the Southern Indian Ocean and South Afric

Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of La Réunion Island

Ozone performs a key role in the middle atmosphere and its monitoring is thus necessary. At the Institute of Applied Physics of the University of Bern, Switzerland, we built a new ground-based microwave radiometer, GROMOS-C (GRound based Ozone MOnitoring System for Campaigns). It has a compact design and can be operated remotely with very little maintenance requirements, being therefore suitable for remote deployments. It has been conceived to measure the vertical distribution of ozone in the middle atmosphere, by observing pressure-broadened emission spectra at a frequency of 110.836 GHz. In addition, meridional and zonal wind profiles can be retrieved, based on the Doppler shift of the ozone line measured in the four directions of observation (north, east, south and west). In June 2014 the radiometer was installed at the Maïdo observatory, on Réunion island (21.2° S, 55.5° E). High-resolution ozone spectra were recorded continuously over 7 months. Vertical profiles of ozone have been retrieved through an optimal estimation inversion process, using the Atmospheric Radiative Transfer Simulator ARTS2 as the forward model. The validation is performed against ozone profiles from the Microwave Limb Sounder (MLS) on the Aura satellite, the ozone lidar located at the observatory and with ozone profiles from weekly radiosondes. Zonal and meridional winds retrieved from GROMOS-C data are validated against another wind radiometer located in situ, WIRA. In addition, we compare both ozone and winds with ECMWF (European Centre for Medium-Range Weather Forecasts) model data. Results show that GROMOS-C provides reliable ozone profiles between 30 and 0.02 hPa. The comparison with lidar profiles shows a very good agreement at all levels. The accordance with the MLS data set is within 5 % for pressure levels between 25 and 0.2 hPa. GROMOS-C's wind profiles are in good agreement with the observations by WIRA and with the model data, differences are below 5 m s−1 for both

First Reprocessing of Southern Hemisphere ADditional OZonesondes Profile Records: 3. Uncertainty in Ozone Profile and Total Column

Reprocessed ozonesonde data from eight SHADOZ (Southern Hemisphere ADditional OZonesondes) sites have been used to derive the first analysis of uncertainty estimates for both profile and total column ozone (TCO). The ozone uncertainty is a composite of the uncertainties of the individual terms in the ozone partial pressure (PO3) equation, those being the ozone sensor current, background current, internal pump temperature, pump efficiency factors, conversion efficiency, and flow rate. Overall, PO3 uncertainties (ΔPO3) are within 15% and peak around the tropopause (15 ± 3 km) where ozone is a minimum and ΔPO3 approaches the measured signal. The uncertainty in the background and sensor currents dominates the overall ΔPO3 in the troposphere including the tropopause region, while the uncertainties in the conversion efficiency and flow rate dominate in the stratosphere. Seasonally, ΔPO3 is generally a maximum in the March–May, with the exception of SHADOZ sites in Asia, for which the highest ΔPO3 occurs in September–February. As a first approach, we calculate sonde TCO uncertainty (ΔTCO) by integrating the profile ΔPO3 and adding the ozone residual uncertainty, derived from the McPeters and Labow (2012, doi:10.1029/2011JD017006) 1σ ozone mixing ratios. Overall, ΔTCO are within ±15 Dobson units (DU), representing ~5–6% of the TCO. Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument (TOMS and OMI) satellite overpasses are generally within the sonde ΔTCO. However, there is a discontinuity between TOMS v8.6 (1998 to September 2004) and OMI (October 2004–2016) TCO on the order of 10 DU that accounts for the significant 16 DU overall difference observed between sonde and TOMS. By comparison, the sonde‐OMI absolute difference for the eight stations is only ~4 DU