FRESCO+: an improved O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; A-band cloud retrieval algorithm for tropospheric trace gas retrievals

Wang, P.; Stammes, P.; A, R. van der; Pinardi, Gaia; Roozendaël, Michel Van

doi:10.5194/acpd-8-9697-2008

Cited by 44 publications

(66 citation statements)

References 21 publications

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“…Cloud pressure and cloud fraction are retrieved using the Fast Retrieval Scheme for Clouds from the Oxygen A‐band (FRESCO) applied to SCIAMACHY measurements [ Wang et al , 2008]. FRESCO retrieves cloud pressure (CP) and effective cloud fraction (CF) by fitting the measured reflectance in and around the O 2 ‐A absorption band at 760 nm with modeled reflectances for scenes with different cloud fractions and cloud pressures.…”

Section: Datamentioning

confidence: 99%

“…The depth of the O 2 A‐band is proportional to the oxygen column above the surface or cloud, which is used to determine the height of a cloud. FRESCO cloud pressure is close to the optical mid‐level of the cloud [ Wang et al , 2008]. The sensitivity of cloud pressure retrievals, from various instruments and algorithms, to absorbing aerosol layers was shown using ‘Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar’ (PARASOL) observations, for a case with an absorbing aerosol layer (fine‐mode fraction AOT < 0.3) located between 2 and 4 km above low‐level clouds at around 1 km altitude (determined from CALIOP measurements) [ Waquet et al , 2009].…”

Section: Datamentioning

confidence: 99%

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Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry

et al. 2012

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[1] The solar radiative absorption by an aerosol layer above clouds is quantified using passive satellite spectrometry from the ultraviolet (UV) to the shortwave infrared (SWIR). UV-absorbing aerosols have a strong signature that can be detected using UV reflectance measurements, even when above clouds. Since the aerosol extinction optical thickness decreases rapidly with increasing wavelength for biomass burning aerosols, the properties of the clouds below the aerosol layer can be retrieved in the SWIR, where aerosol extinction optical thickness is sufficiently small. Using radiative transfer computations, the contribution of the clouds to the reflected radiation can be modeled for the entire solar spectrum. In this way, cloud and aerosol effects can be separated for a scene with aerosols above clouds. Aerosol microphysical assumptions and retrievals are avoided by modeling only the pure (aerosol-free) cloud spectra. An algorithm was developed using the spaceborne spectrometer Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). The aerosol direct radiative effect (DRE) over clouds over the South Atlantic Ocean west of Africa, averaged through August 2006 was found to be 23 AE 8 Wm À2 with a mean variation over the region in this month of 22 Wm À2 . The largest aerosol DRE over clouds found in that month was 132 AE 8 Wm À2 . The algorithm can be applied to any instrument, or a combination of instruments, that measures UV, visible and SWIR reflectances at the top of the atmosphere (TOA) simultaneously.Citation: de Graaf, M., L. G. Tilstra, P. Wang, and P. Stammes (2012), Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry,

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Section: Datamentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry

et al. 2012

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“…An appropriate cloud correction is particularly important for measurements close to strong emission sources. We considered the influence of the actual effective cloud fraction and ef- fective cloud top height using simultaneously retrieved cloud properties from the FRESCO+ algorithm (Koelemeijer et al, 2001;Wang et al, 2008). For the cloud top albedo we assumed a value of 40 %, which is about half of the value at 760 nm (see e.g., Nakajima and King, 1990), at which the FRESCO+ cloud algorithm is applied.…”

Section: Cloud Correction Algorithmmentioning

confidence: 99%

“…For the comparison with MOPITT observations we selected SCIAMACHY observations above low-lying clouds (cloud top heights between 0 and 2 km and effective cloud fractions > 20 %), for which the SCIAMACHY observations have a similar heightdependent sensitivity compared to MOPITT. The cloud properties are derived from the FRESCO+ algorithm, see Koelemeijer et al (2001) and Wang et al (2008). The height dependent averaging kernels of the individual SCIAMACHY observations (see Sect.…”

Section: Problems Of the Sciamachy Co Retrievals And Possible Correctmentioning

confidence: 99%

Application of SCIAMACHY and MOPITT CO total column measurements to evaluate model results over biomass burning regions and Eastern China

et al. 2011

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Abstract. We developed a new CO vertical column density product from near IR observations of the SCIAMACHY instrument onboard ENVISAT. For the correction of a temporally and spatially variable offset of the CO vertical column densities we apply a normalisation procedure based on coincident MOPITT (version 4) observations over the oceans. The resulting normalised SCIAMACHY CO data is well suited for the investigation of the CO distribution over continents, where important emission sources are located. We use only SCIAMACHY observations for effective cloud fractions below 20 %. Since the remaining effects of clouds can still be large (up to 100 %), we applied a cloud correction scheme which explicitly considers the cloud fraction, cloud top height and surface albedo of individual observations. The normalisation procedure using MOPITT data and the cloud correction substantially improve the agreement with independent data sets. We compared our new SCIAMACHY CO data set, and also observations from the MOPITT instrument, to the results from three global atmospheric chemistry models (MATCH, EMAC at low and high resolution, and GEOS-Chem); the focus of this comparison is on regions with strong CO emissions (from biomass burning or anthropogenic sources). The comparison indicates that over most of these regions the seasonal cycle is generally captured well but the simulated CO vertical column densities Correspondence to: T. Wagner (thomas.wagner@mpic.de) are systematically smaller than those from the satellite observations, in particular with respect to SCIAMACHY observations. Because SCIAMACHY is more sensitive to the lowest part of the atmosphere compared to MOPITT, this indicates that especially close to the surface the model simulations systematically underestimate the true atmospheric CO concentrations, probably caused by an underestimation of CO emissions by current emission inventories. For some biomass burning regions, however, such as Central Africa in July-August, model results are also found to be higher than the satellite observations.

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“…For the cloudy AMF, we use cloud top and optical depths from the GEOS-5 meteorology fields. Scenes with cloud fraction, estimated using the oxygen A band [Wang et al, 2008;Koelemeijer et al, 2002], greater than 40% are removed from subsequent analyses. We acknowledge that some cloudy scenes may be misidentified as aerosols and vice versa.…”

Section: Sciamachy Hcho Columnsmentioning

confidence: 99%

Biomass burning emission estimates inferred from satellite column measurements of HCHO: Sensitivity to co-emitted aerosol and injection height

Gonzi

Palmer

Barkley

et al. 2011

Geophys. Res. Lett.

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[1] We infer monthly regional biomass burning emissions of formaldehyde (HCHO) during 2006 from space-borne column measurements of HCHO from the SCIAMACHY instrument over Canada, boreal Asia, South America, southern Africa, and Indonesia. We remove the influence of biogenic volatile organic compounds using an offline chemical mechanism. We quantify the sensitivity of our emission estimates to aerosol single scattering albedo, w, indicative of fresh (w = 0.8) and aged (w > 0.9) aerosol, and the relative vertical distribution of the aerosol and HCHO, both which compromise the interpretation of space-based HCHO columns. For our control calculation we assume freshly-emitted gases and aerosols that are mainly confined to the boundary layer. Associated posterior emissions are generally lower than the prior emissions except over Canada and boreal Asia during northern hemisphere summer months. Accounting for faster vertical mixing results in posterior emissions 20%-100% higher than the corresponding control calculation, and consequently more consistent with the prior. Assuming an aged aerosol generally results in a 20% decrease in posterior emissions relative to prior values. Based on the range of posterior estimates from our sensitivity analyses, not accounting for uncertainties associated with the underlying gas-phase and heterogeneous chemistry, we estimate HCHO emission uncertainties are typically 20%-30% but can be up to 300% in extreme cases. Citation: Gonzi, S., P. I. Palmer, M. P. Barkley, I. De Smedt, and M. Van Roozendael (2011), Biomass burning emission estimates inferred from satellite column measurements of HCHO: Sensitivity to co-emitted aerosol and injection height, Geophys. Res. Lett., 38, L14807,

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FRESCO+: an improved O<sub>2</sub> A-band cloud retrieval algorithm for tropospheric trace gas retrievals

Cited by 44 publications

References 21 publications

Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry

Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry

Application of SCIAMACHY and MOPITT CO total column measurements to evaluate model results over biomass burning regions and Eastern China

Biomass burning emission estimates inferred from satellite column measurements of HCHO: Sensitivity to co-emitted aerosol and injection height

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