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Roscoe, H. K.; Johnston, P. V.; Roozendaël, Michel Van; Richter, Andreas; Sarkissian, Alain; Roscoe, John M.; Preston, K. E.; Lambert, J. C.; Hermans, Christian; Decuyper, W.; Dzienus, S.; Winterrath, Tanja; Burrows, J. P.; Goutail, Florence; Pommereau, J.-P.; d’Almeida, Eric; Hottier, J.; Coureul, C.; Didier, Roland; Pundt, I.; Bartlett, L. M.; McElroy, C. T.; Kerr, Jim; Елохов, А. С.; Giovanelli, G.; Ravegnani, F.; Premuda, Margherita; Kostadinov, I.; Erle, F.; Wagner, Thomas; Pfeilsticker, Klaus; Kenntner, Mareike; Marquard, L.; Gil, Manuel; Puentedura, Olga; Yela, Margarita; Arlander, D. W.; Høiskar, Britt Ann Kåstad; Tellefsen, Cathrine W.; Tørnkvist, Kjersti Karlsen; Heese, Birgit; Jones, R. L.; Aliwell, S. R.; Freshwater, Ray

doi:10.1023/a:1006111216966

Cited by 66 publications

(14 citation statements)

References 28 publications

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“…procedure (Platt, 1994). SAOZ performances have been continuously evaluated by regular comparisons with UV-vis independent observations (e.g., Hofmann et al, 1995;Roscoe et al, 1999;Hendrick et al, 2011). The SAOZ precision is 4.7 %, while the SAOZ total accuracy is 5.9 % (Hendrick et al, 2011).…”

Section: Comparison With Ground-based Saoz Datamentioning

confidence: 99%

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

et al. 2016

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Ozone Monitoring Experiment-2 (GOME-2) launched on board MetOp-A and Brewer-Dobson data show that, on average, IASI overestimates the ultraviolet (UV) data by 5-6 % with the largest differences found in the southern high latitudes. The comparison with UV-visible SAOZ (Système d'Analyse par Observation Zénithale) measurements shows a mean bias between IASI and SAOZ TOCs of 2-4 % in the midlatitudes and tropics and 7 % at the polar circle. Part of the discrepancies found at high latitudes can be attributed to the limited information content in the observations due to low brightness temperatures. The comparison with ozonesonde vertical profiles (limited to 30 km) shows that on average IASI with FORLI processing underestimates O 3 by ∼ 5-15 % in the troposphere while it overestimates O 3 by ∼ 10-40 % in the stratosphere, depending on the latitude. The largest relative differences are found in the tropPublished by Copernicus Publications on behalf of the European Geosciences Union. 4328A. Boynard et al.: Seven years of IASI ozone retrievals from FORLI ical tropopause region; this can be explained by the low O 3 amounts leading to large relative errors. In this study, we also evaluate an updated version of FORLI-O3 retrieval software (v20151001), using look-up tables recalculated to cover a larger spectral range using the latest HITRAN spectroscopic database (HITRAN 2012) and implementing numerical corrections. The assessment of the new O 3 product with the same set of observations as that used for the validation exercise shows a correction of ∼ 4 % for the TOC positive bias when compared to the UV ground-based and satellite observations, bringing the overall global comparison to ∼ 1-2 % on average. This improvement is mainly associated with a decrease in the retrieved O 3 concentration in the middle stratosphere (above 30 hPa/25 km) as shown by the comparison with ozonesonde data.

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Section: Comparison With Ground-based Saoz Datamentioning

confidence: 99%

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

et al. 2016

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“…As this is an important limitation for the use of MAX-DOAS measurements in a global observing system, the Network for the Detection of Atmospheric Composition Change NDACC (formerly known as NDSC) has organized several intercomparison campaigns aimed at comparing instruments, retrievals and uncertainties of a wide range of DOAS instruments. The first of these campaigns were focused entirely on zenith-sky observations for stratospheric absorbers (Hofmann et al, 1995;Vaughan et al, 1997;Roscoe et al, 1999) but later also included other viewing directions (Vandaele et al, 2005). The Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI) campaign in 2009 in Cabauw, the Netherlands Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Investigating differences in DOAS retrieval codes using MAD-CAT campaign data

et al. 2017

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Abstract. The differential optical absorption spectroscopy (DOAS) method is a well-known remote sensing technique that is nowadays widely used for measurements of atmospheric trace gases, creating the need for harmonization and characterization efforts. In this study, an intercomparison exercise of DOAS retrieval codes from 17 international groups is presented, focusing on NO 2 slant columns. The study is based on data collected by one instrument during the MultiAxis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) in Mainz, Germany, in summer 2013. As data from the same instrument are used by all groups, the results are free of biases due to instrumental differences, which is in contrast to previous intercomparison exercises.While in general an excellent correlation of NO 2 slant columns between groups of > 99.98 % (noon reference fits) and > 99.2 % (sequential reference fits) for all elevation angles is found, differences between individual retrievals are as large as 8 % for NO 2 slant columns and 100 % for rms residuals in small elevation angles above the horizon.Comprehensive sensitivity studies revealed that absolute slant column differences result predominantly from the choice of the reference spectrum while relative differences originate from the numerical approach for solving the DOAS equation as well as the treatment of the slit function. Furthermore, differences in the implementation of the intensity offset correction were found to produce disagreements for measurements close to sunrise (8-10 % for NO 2 , 80 % for rms residual). The largest effect of ≈ 8 % difference in NO 2 was found to arise from the reference treatment; in particular for fits using a sequential reference. In terms of rms fit residual, the reference treatment has only a minor impact. In contrast, the wavelength calibration as well as the intensity offset correction were found to have the largest impact (up to 80 %) on rms residual while having only a minor impact on retrieved NO 2 slant columns.

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“…gov/data/) and have been successfully intercompared for NO 2 in ad hoc international exercises (Roscoe et al, 1999(Roscoe et al, , 2010Vandaele et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Hemispheric asymmetry in stratospheric NO<sub>2</sub> trends

et al. 2017

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Abstract. Over 20 years of stratospheric NO 2 vertical column density (VCD) data from ground-based zenith DOAS spectrometers were used for trend analysis, specifically, via multiple linear regression. Spectrometers from the Network for the Detection of Atmospheric Composition Change (NDACC) cover the subtropical latitudes in the Northern Hemisphere (Izaña, 28 • N), the southern Subantarctic (Ushuaia, 55 • S) and Antarctica (Marambio, 64 • S, and Belgrano, 78 • S). The results show that for the period 1993-2014, a mean positive decadal trend of +8.7 % was found in the subtropical Northern Hemisphere stations, and negative decadal trends of −8.7 and −13.8 % were found in the Southern Hemisphere at Ushuaia and Marambio, respectively; all trends are statistically significant at 95 %. Belgrano only shows a significant decadal trend of −11.3 % in the summer/autumn period. Most of the trends result from variations after 2005. The trend in the diurnal build-up per hour (DBU) was used to estimate the change in the rate of N 2 O 5 conversion to NO 2 during the day. With minor differences, the results reproduce those obtained for NO 2 . The trends computed for individual months show large monthto-month variability. At Izaña, the maximum occurs in December (+13.1 %), dropping abruptly to lower values in the first part of the year. In the Southern Hemisphere, the polar vortex dominates the monthly distributions of the trends. At Marambio, the maximum occurs in mid-winter (−21 %), whereas at the same time, the Ushuaia trend is close to its annual minimum (−7 %). The large difference in the trends at these two relatively close stations suggests a vortex shift towards the Atlantic/South American area over the past few years. Finally, the hemispheric asymmetry obtained in this work is discussed in the framework of the results obtained by previous works that considered tracer analysis and BrewerDobson circulation. The results obtained here provide evidence that the NO 2 produced by N 2 O decomposition is not the only cause of the observed trend in the stratosphere and support recent publications pointing to a dynamical redistribution starting in the past decade.

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Cited by 66 publications

References 28 publications

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

Investigating differences in DOAS retrieval codes using MAD-CAT campaign data

Hemispheric asymmetry in stratospheric NO<sub>2</sub> trends

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Cited by 66 publications

References 28 publications

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

Investigating differences in DOAS retrieval codes using MAD-CAT campaign data

Hemispheric asymmetry in stratospheric NO&lt;sub&gt;2&lt;/sub&gt; trends

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Hemispheric asymmetry in stratospheric NO<sub>2</sub> trends