Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

Mzé, Nahoudha; Hauchecorne, Alain; Benchérif, Hassan; Dalaudier, Francis; Bertaux, Jean-Loup

doi:10.5194/acp-10-8025-2010

Cited by 11 publications

(10 citation statements)

References 29 publications

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“…Meijer et al (2004) but on a significantly larger dataset and found large GOMOS positive bias, over 40 %, in the tropical UTLS and below. This conclusion is in full agreement with the validation work of Mze et al (2010) using ozone soundings from eight SHADOZ stations. The validation studies performed so far (which are also focused mainly on the stratospheric ozone) indicate, however, the presence of large GOMOS ozone bias in UTLS also in IPF v6 data.…”

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confidence: 80%

Improved GOMOS/Envisat ozone retrievals in the upper troposphere and the lower stratosphere

et al. 2017

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International audienceGlobal Ozone Monitoring by Occultation of Stars (GOMOS) on board Envisat has performed about 440 000 night-time occultations during 2002–2012. Self-calibrating measurement principle, good vertical resolution, excellent pointing accuracy and the wide vertical range from the troposphere up to the lower thermosphere make GOMOS profiles interesting for different analyses. The GOMOS ozone data are of high quality in the stratosphere and the mesosphere, but the current operational retrieval algorithm (IPF v.6) is not optimized for retrievals in the upper troposphere–lower stratosphere (UTLS). In particular, validation of GOMOS profiles against ozonesonde data has revealed a substantial positive bias (up to 100 %) in the UTLS region. The retrievals in the UTLS are challenging because of low signal-to-noise ratio and the presence of clouds. In this work, we discuss the reasons for the systematic uncertainties in the UTLS with the IPF v.6 algorithm or its modifications based on simultaneous retrievals of several constituents using the full visible wavelength range. The main reason is high sensitivity of the UTLS retrieval algorithms to an assumed aerosol extinction model. We have developed a new aerosol–insensitive ozone profile inversion algorithm for GOMOS data in the UTLS using a DOAS-type method at visible wavelengths. The method uses minimal assumptions about the atmospheric profiles. The ozone retrievals in the whole altitude range from the troposphere to the lower thermosphere are performed in two steps, as in the operational algorithm: spectral inversion followed by the vertical inversion. The horizontal column ozone densities retrieved in the spectral inversion follow V6 profiles in the middle atmosphere and follow the triplet ozone profiles in the UTLS. The vertical inversion is performed as in IPF v6 with the Tikhonov-type regularization according to the target resolution. The validation of new retrieved ozone profiles with ozonesondes show dramatic reduction of GOMOS ozone biases in the UTLS. The new GOMOS ozone profiles are also in a very good agreement with measurements by MIPAS, ACE-FTS and OSIRIS satellite instruments in the UTLS. It is also shown that the known geophysical phenomena in the UTLS ozone are well reproduced with the new GOMOS data

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confidence: 80%

Improved GOMOS/Envisat ozone retrievals in the upper troposphere and the lower stratosphere

et al. 2017

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“…Lidar has a better vertical resolution mainly in the lower stratosphere, but is limited to the lower part (15-45 km). This section does not intend to present a large scale validation of GOMOS using a larger set of instruments as this is covered by other publications (e.g., Meijer et al, 2004;Mze et al, 2010;van Gijsel et al, 2010). Here the main objective consists of assessing the long-term evolution and confirming the validity of the tests presented previously in Sect.…”

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confidence: 99%

Mid-latitude ozone monitoring with the GOMOS-ENVISAT experiment version 5: the noise issue

et al. 2010

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Abstract. The GOMOS ozone profiles have been analysed to evaluate the GOMOS ability to capture the long-term ozone evolution at mid-latitudes during the expected recovery phase of the ozone layer. Version 5 of the operational GOMOS ozone data has been compared with data from two of the longest ground-based instruments based on different techniques and already involved with many other previous space instrument validations. Comparisons between ground-based and GOMOS data confirm the occurrence of spurious retrievals mainly occurring since 2006. Using a selected set of data it is shown that some bad retrievals are induced by the increasing dark charge of the detectors combined with an inadequate method for its correction. This effect does not only induce a continuous bias, but is rather exhibiting a bimodal distribution including the correct profiles and the bad retrievals. For long-term analyses it is recommended filtering the data according to background light conditions and star temperature (spectrum shape). The new method of the dark charge estimate proposed to be implemented in the version 6 of the ESA algorithm seems to significantly reduce the occurrence of such effects and should allow to monitor stratospheric ozone using GOMOS data with greater confidence.

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“…While the frequency, seasonality, and impacts of STT events have been well described in the tropics and Northern Hemisphere (NH), observational estimates from the SH extratropics are noticeably absent in the literature. The role of STT in the SH remains highly uncertain due to the more limited data availability compared to the NH and the temporal sparsity of these datasets (Mze et al, 2010;Thompson et al, 2014;Liu et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

et al. 2017

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Abstract. Stratosphere-to-troposphere transport (STT) provides an important natural source of ozone to the upper troposphere, but the characteristics of STT events in the Southern Hemisphere extratropics and their contribution to the regional tropospheric ozone budget remain poorly constrained. Here, we develop a quantitative method to identify STT events from ozonesonde profiles. Using this method we estimate the seasonality of STT events and quantify the ozone transported across the tropopause over Davis (69 • S, 2006Davis (69 • S, -2013, Macquarie Island (54 • S, 2004-2013), and Melbourne (38 • S, 2004-2013). STT seasonality is determined by two distinct methods: a Fourier bandpass filter of the vertical ozone profile and an analysis of the Brunt-Väisälä frequency. Using a bandpass filter on 7-9 years of ozone profiles from each site provides clear detection of STT events, with maximum occurrences during summer and minimum during winter for all three sites. The majority of tropospheric ozone enhancements owing to STT events occur within 2.5 and 3 km of the tropopause at Davis and Macquarie Island respectively. Events are more spread out at Melbourne, occurring frequently up to 6 km from the tropopause. The mean fraction of total tropospheric ozone attributed to STT during STT events is ∼ 1.0-3.5 % at each site; however, during individual events, over 10 % of tropospheric ozone may be directly transported from the stratosphere. The cause of STTs is determined to be largely due to synoptic low-pressure frontal systems, determined using coincident ERA-Interim reanalysis meteorological data. Ozone enhancements can also be caused by biomass burning plumes transported from Africa and South America, which are apparent during austral winter and spring and are determined using satellite measurements of CO. To provide regional context for the ozonesonde observations, we use the GEOS-Chem chemical transport model, which is too coarsely resolved to distinguish STT events but is able to accurately simulate the seasonal cycle of tropospheric ozone columns over the three southern hemispheric sites. Combining the ozonesonde-derived STT event characteristics with the simulated tropospheric ozone columns from GEOS-Chem, we estimate STT ozone flux near the three sites and see austral summer dominated yearly amounts of between 5.7 and 8.7 × 10 17 molecules cm −2 a −1 .

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Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

Cited by 11 publications

References 29 publications

Improved GOMOS/Envisat ozone retrievals in the upper troposphere and the lower stratosphere

Improved GOMOS/Envisat ozone retrievals in the upper troposphere and the lower stratosphere

Mid-latitude ozone monitoring with the GOMOS-ENVISAT experiment version 5: the noise issue

Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

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