Linear trends in cloud top height from passive observations in the oxygen A-band

Lelli, Luca; Kokhanovsky, Alexander A.; Розанов, В. В.; Vountas, Marco; Burrows, J. P.

doi:10.5194/acp-14-5679-2014

Cited by 37 publications

(31 citation statements)

References 41 publications

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“…Moreover, tropospheric temperature structure has been relatively constant amidst a global ~1 K warming [ Santer et al ., ]. Finally, a recent global satellite‐based time series analysis found that cloud top heights (a proxy for the vertical extent of tropical circulation relevant to Δ 36, T equil ) had a long‐term trend of ≤ 2 m yr −1 between 1996 and 2011 [ Lelli et al ., ], too small to be detectable by Δ 36 , even when extrapolated back to 1978. The most important atmospheric trend from 1978 to 2013 for surface Δ 36 values was therefore that of an increasing tropospheric O 3 burden.…”

Section: Resultsmentioning

confidence: 99%

Isotopic ordering in atmospheric O₂ as a tracer of ozone photochemistry and the tropical atmosphere

et al. 2016

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The distribution of isotopes within O2 molecules can be rapidly altered when they react with atomic oxygen. This mechanism is globally important: while other contributions to the global budget of O2 impart isotopic signatures, the O(3P) + O2 reaction resets all such signatures in the atmosphere on subdecadal timescales. Consequently, the isotopic distribution within O2 is determined by O3 photochemistry and the circulation patterns that control where that photochemistry occurs. The variability of isotopic ordering in O2 has not been established, however. We present new measurements of 18O18O in air (reported as Δ36 values) from the surface to 33 km altitude. They confirm the basic features of the clumped‐isotope budget of O2: Stratospheric air has higher Δ36 values than tropospheric air (i.e., more 18O18O), reflecting colder temperatures and fast photochemical cycling of O3. Lower Δ36 values in the troposphere arise from photochemistry at warmer temperatures balanced by the influx of high‐Δ36 air from the stratosphere. These observations agree with predictions derived from the GEOS‐Chem chemical transport model, which provides additional insight. We find a link between tropical circulation patterns and regions where Δ36 values are reset in the troposphere. The dynamics of these regions influences lapse rates, vertical and horizontal patterns of O2 reordering, and thus the isotopic distribution toward which O2 is driven in the troposphere. Temporal variations in Δ36 values at the surface should therefore reflect changes in tropospheric temperatures, photochemistry, and circulation. Our results suggest that the tropospheric O3 burden has remained within a ±10% range since 1978.

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Section: Resultsmentioning

confidence: 99%

Isotopic ordering in atmospheric O₂ as a tracer of ozone photochemistry and the tropical atmosphere

et al. 2016

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“…1) which lies below the physical CTH (Ziemke et al, 2008). SACURA CTH retrieval algorithm (Kokhanovsky et al, 2005), however, takes into account radiative transfer inside, above, and below the clouds (Lelli et al, 2014). Therefore, it provides more realistic CTHs.…”

Section: The Ccd Methodsmentioning

confidence: 99%

Tropical tropospheric ozone columns from nadir retrievals of GOME-1/ERS-2, SCIAMACHY/Envisat, and GOME-2/MetOp-A (1996–2012)

et al. 2016

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Abstract. Tropical tropospheric ozone columns are retrieved with the convective cloud differential (CCD) technique using total ozone columns and cloud parameters from different European satellite instruments. Monthlymean tropospheric column amounts [DU] are calculated by subtracting the above-cloud ozone column from the total column. A CCD algorithm (CCD_IUP) has been developed as part of the verification algorithm developed for TROPOspheric Monitoring Instrument (TROPOMI) on Sentinel 5-precursor (S5p) mission, which was applied to GOME/ ERS-2 (1995ERS-2 ( -2003, SCIAMACHY/ Envisat (2002-2012, and GOME-2/MetOp-A (2007-2012) measurements. Thus a unique long-term record of monthly-mean tropical tropospheric ozone columns (20 • S-20 • N) from 1996 to 2012 is now available. An uncertainty estimation has been performed, resulting in a tropospheric ozone column uncertainty less than 2 DU (< 10 %) for all instruments. The dataset has not been yet harmonised into one consistent; however, comparison between the three separate datasets (GOME/SCIAMACHY/GOME-2) shows that GOME-2 overestimates the tropical tropospheric ozone columns by about 8 DU, while SCIAMACHY and GOME are in good agreement. Validation with Southern Hemisphere ADditional OZonesondes (SHADOZ) data shows that tropospheric ozone columns from the CCD_IUP technique and collocated integrated ozonesonde profiles from the surface up to 200 hPa are in good agreement with respect to range, interannual variations, and variances. Biases within ±5 DU and root-mean-square (RMS) deviation of less than 10 DU are found for all instruments. CCD comparisons using SCIA-MACHY data with tropospheric ozone columns derived from limb/nadir matching have shown that the bias and RMS deviation are within the range of the CCD_IUP comparison with the ozonesondes. The 17-year dataset can be helpful for evaluating chemistry models and performing climate change studies.

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“…Finally, we remark that a companion paper (Lelli et al, 2016) in this issue describes a science verification of the Aerosol Layer Height algorithm using observations of an optically thick volcanic ash plume near Iceland in May 2010.…”

Section: Introductionmentioning

confidence: 99%

“…Note that in all three retrieval setups, (i) the assumed cloud profile is a scattering layer with constant particle volume extinction coefficient or an isotropically reflecting surface, (ii) the cloud covers the ground pixel with a particular cloud fraction, and (iii) the ground surface albedo is taken from climatologies and fixed in retrieval. Much experience with application of these retrieval schemes to various satellite instruments (GOME-2, GOME: Global Ozone Monitoring Experiment, SCIAMACHY: SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) has been built up over the past years (e.g., Lelli et al, 2012Lelli et al, , 2014Wang and Stammes, 2014;Wang et al, 2008;Loyola et al, 2007;Kokhanovsky et al, 2006a, b;Koelemeijer et al, 2001Koelemeijer et al, , 2002.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the operational Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor: application to O<sub>2</sub> A band observations from GOME-2A

et al. 2015

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Abstract. An algorithm setup for the operational Aerosol Layer Height product for TROPOMI on the Sentinel-5 Precursor mission is described and discussed, applied to GOME-2A data, and evaluated with lidar measurements. The algorithm makes a spectral fit of reflectance at the O 2 A band in the near-infrared and the fit window runs from 758 to 770 nm. The aerosol profile is parameterised by a scattering layer with constant aerosol volume extinction coefficient and aerosol single scattering albedo and with a fixed pressure thickness. The algorithm's target parameter is the height of this layer. In this paper, we apply the algorithm to observations from GOME-2A in a number of systematic and extensive case studies, and we compare retrieved aerosol layer heights with lidar measurements. Aerosol scenes cover various aerosol types, both elevated and boundary layer aerosols, and land and sea surfaces. The aerosol optical thicknesses for these scenes are relatively moderate. Retrieval experiments with GOME-2A spectra are used to investigate various sensitivities, in which particular attention is given to the role of the surface albedo.From retrieval simulations with the single-layer model, we learn that the surface albedo should be a fit parameter when retrieving aerosol layer height from the O 2 A band. Current uncertainties in surface albedo climatologies cause biases and non-convergences when the surface albedo is fixed in the retrieval. Biases disappear and convergence improves when the surface albedo is fitted, while precision of retrieved aerosol layer pressure is still largely within requirement levels. Moreover, we show that fitting the surface albedo helps to ameliorate biases in retrieved aerosol layer height when the assumed aerosol model is inaccurate. Subsequent retrievals with GOME-2A spectra confirm that convergence is better when the surface albedo is retrieved simultaneously with aerosol parameters. However, retrieved aerosol layer pressures are systematically low (i.e., layer high in the atmosphere) to the extent that retrieved values no longer realistically represent actual extinction profiles. When the surface albedo is fixed in retrievals with GOME-2A spectra, convergence deteriorates as expected, but retrieved aerosol layer pressures become much higher (i.e., layer lower in atmosphere). The comparison with lidar measurements indicates that retrieved aerosol layer heights are indeed representative of the underlying profile in that case. Finally, subsequent retrieval simulations with two-layer aerosol profiles show that a model error in the assumed profile (two layers in the simulation but only one in the retrieval) is partly absorbed by the surface albedo when this parameter is fitted. This is expected in view of the correlations between errors in fit parameters and the effect is relatively small for elevated layers (less than 100 hPa). If one of the scattering layers is near the surface (boundary layer aerosols), the effect becomes surprisingly large, in such a way that the retrieved height of the sin...

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Linear trends in cloud top height from passive observations in the oxygen A-band

Cited by 37 publications

References 41 publications

Isotopic ordering in atmospheric O₂ as a tracer of ozone photochemistry and the tropical atmosphere

Isotopic ordering in atmospheric O₂ as a tracer of ozone photochemistry and the tropical atmosphere

Tropical tropospheric ozone columns from nadir retrievals of GOME-1/ERS-2, SCIAMACHY/Envisat, and GOME-2/MetOp-A (1996–2012)

Evaluation of the operational Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor: application to O<sub>2</sub> A band observations from GOME-2A

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Linear trends in cloud top height from passive observations in the oxygen A-band

Cited by 37 publications

References 41 publications

Isotopic ordering in atmospheric O2 as a tracer of ozone photochemistry and the tropical atmosphere

Isotopic ordering in atmospheric O2 as a tracer of ozone photochemistry and the tropical atmosphere

Tropical tropospheric ozone columns from nadir retrievals of GOME-1/ERS-2, SCIAMACHY/Envisat, and GOME-2/MetOp-A (1996–2012)

Evaluation of the operational Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor: application to O&lt;sub&gt;2&lt;/sub&gt; A band observations from GOME-2A

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Product

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Isotopic ordering in atmospheric O₂ as a tracer of ozone photochemistry and the tropical atmosphere

Isotopic ordering in atmospheric O₂ as a tracer of ozone photochemistry and the tropical atmosphere

Evaluation of the operational Aerosol Layer Height retrieval algorithm for Sentinel-5 Precursor: application to O<sub>2</sub> A band observations from GOME-2A