Global stratospheric aerosol extinction profile retrievals from SCIAMACHY limb-scatter observations

Abstract. Stratospheric aerosol extinction profiles are retrieved from SCIAMACHY/Envisat limb-scatter observations in the visible spectral range. The retrieval algorithm is based on a colour-index approach using the normalized limb-radiance profiles at 470 nm and 750 nm wavelength. The optimal estimation approach in combination with the radiative transfer model SCIATRAN is employed for the retrievals. This study presents a detailed description of the retrieval algorithm, and a sensitivity analysis investigating the impact of the most important parameters that affect the aerosol extinction profile retrieval accuracy. It is found that the parameter with the largest impact is surface albedo, particularly for SCIAMACHY observations in the Southern Hemisphere where the error in stratospheric aerosol extinction can be up to 50% if the surface albedo is not well known. The effect of errors in the assumed ozone and neutral density profiles on the aerosol profile retrievals is with generally less than 6% relatively small. The aerosol extinction profiles retrieved from SCIAMACHY are compared with co-located SAGE II solar occultation measurements of stratospheric aerosol extinction during the period 2003–2005. The mean aerosol extinction profiles averaged over all co-locations agree to within 20% between 15 and 35 km altitude. However, larger differences are observed at specific latitudes.

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The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 aerosol extinction retrieval algorithm: theoretical basis

Atmospheric Measurement Techniques ◽

10.5194/amt-11-2633-2018 ◽

2018 ◽

Vol 11 (5) ◽

pp. 2633-2651 ◽

Cited By ~ 13

Author(s):

Robert Loughman ◽

Pawan K. Bhartia ◽

Zhong Chen ◽

Philippe Xu ◽

Ernest Nyaku ◽

...

Keyword(s):

Spherical Shell ◽

Theoretical Basis ◽

Relaxation Method ◽

Radiative Transfer Model ◽

Aerosol Size Distribution ◽

Retrieval Algorithm ◽

Transfer Model ◽

Aerosol Extinction ◽

Horizontal Variations

Abstract. The theoretical basis of the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 aerosol extinction retrieval algorithm is presented. The algorithm uses an assumed bimodal lognormal aerosol size distribution to retrieve aerosol extinction profiles at 675 nm from OMPS LP radiance measurements. A first-guess aerosol extinction profile is updated by iteration using the Chahine nonlinear relaxation method, based on comparisons between the measured radiance profile at 675 nm and the radiance profile calculated by the Gauss–Seidel limb-scattering (GSLS) radiative transfer model for a spherical-shell atmosphere. This algorithm is discussed in the context of previous limb-scattering aerosol extinction retrieval algorithms, and the most significant error sources are enumerated. The retrieval algorithm is limited primarily by uncertainty about the aerosol phase function. Horizontal variations in aerosol extinction, which violate the spherical-shell atmosphere assumed in the version 1 algorithm, may also limit the quality of the retrieved aerosol extinction profiles significantly.

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Space-borne measurements of mesospheric magnesium species – a retrieval algorithm and preliminary profiles

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-1963-2008 ◽

2008 ◽

Vol 8 (7) ◽

pp. 1963-1983 ◽

Cited By ~ 15

Author(s):

M. Scharringhausen ◽

A. C. Aikin ◽

J. P. Burrows ◽

M. Sinnhuber

Keyword(s):

Wavelength Range ◽

Optimal Estimation ◽

Global Scale ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Transfer Model ◽

Resonance Fluorescence ◽

Altitude Range ◽

Air Density ◽

Metallic Species

Abstract. We present a joint retrieval as well as first results for mesospheric air density and mesospheric Magnesium species (Mg and Mg+) using limb data from the SCIAMACHY instrument on board the European ENVISAT satellite.considered. These species feature Metallic species like neutral Mg, ionized Mg+ and others (Fe, Si, Li, etc.) ablate from meteoric dust, enter the gas phase and occur at high altitudes (≥70 km). Emissions from these species are clearly observed in the SCIAMACHY limb measurements. These emissions are used to retrieve total and thermospheric column densities as well as preliminary profiles of metallic species in the altitude range of 70–92 km. In this paper, neutral Magnesium as well as its ionized counterpart Mg+ is considered. These species feature resonance fluorescence in the wavelength range 279 and 285 nm and thus have a rather simple excitation process. A radiative transfer model (RTM) for the mesosphere has been developed and validated. Based on a ray tracing kernel, radiances in a large wavelength range from 240–300 nm covering limb as well as nadir geometry can be calculated. The forward model has been validated and shows good agreement with established models in the given wavelength range and a large altitude range. The RTM has been coupled to a retrieval based on Optimal Estimation. Air density is retrieved from Rayleigh backscattered light. Mesospheric Mg and Mg+ number densities are retrieved from their emission signals observed in the limb scans of SCIAMACHY. Other species like iron, silicon, OH and NO can be investigated in principle with the same algorithm. Based on the retrieval presented here, SCIAMACHY offers the opportunity to investigate mesospheric species on a global scale and with good vertical resolution for the first time.

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Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A-band

10.5194/amt-2017-323 ◽

2017 ◽

Author(s):

Swadhin Nanda ◽

Martin de Graaf ◽

Maarten Sneep ◽

Johan F. de Haan ◽

Piet Stammes ◽

...

Keyword(s):

Optical Thickness ◽

Surface Albedo ◽

High Surface ◽

Aerosol Optical Thickness ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Transfer Model ◽

Aerosol Layer ◽

Critical Surface ◽

Layer Height

Abstract. Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top of atmosphere reflectance spectrum in the oxygen A-band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top of atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A-band, and discusses its implications. The underlying physics are introduced by analysing top of atmosphere reflectance spectra obtained using a radiative transfer model. Furthermore, error analysis of the aerosol layer height retrieval algorithm are conducted over dark and bright surfaces to show the dependency on surface reflectance. The analysis shows that the information on aerosol layer height from atmospheric path contribution and the surface contribution to the top of atmosphere are opposite in sign – an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these contributions are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A-band from GOME-2A instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

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Impact of 3D cloud structures on tropospheric NO2 column measurements from UV-VIS sounders

10.5194/egusphere-egu21-7523 ◽

2021 ◽

Author(s):

Huan Yu ◽

Arve Kylling ◽

Claudia Emde ◽

Bernhard Mayer ◽

Michel Van Roozendael ◽

...

Keyword(s):

Radiative Transfer ◽

Synthetic Data ◽

Sensitivity Study ◽

Trace Gas ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Transfer Model ◽

Boundary Layer Clouds ◽

Cloud Parameters ◽

The Impact

<p>Operational retrievals of tropospheric trace gases from space-borne spectrometers are made using 1D radiative transfer models. To minimize cloud effects generally only partially cloudy pixels are analysed using simplified cloud contamination treatments based on radiometric cloud fraction estimates and photon path length corrections based on oxygen collision pair (O2-O2) or O2A-absorption band measurements. In reality, however, the impact of clouds can be much more complex, involving unresolved sub-pixel clouds, scattering of clouds in neighbouring pixels, and cloud shadow effects, such that 3D radiation scattering from unresolved boundary layer clouds may give significant biases in the trace gas retrievals. In order to quantify this impact, we use the MYSTIC 3D radiative transfer model to generate synthetic data. The realistic 3D cloud fields, needed for MYSTIC input, are generated by the ICOsahedral Non-hydrostatic (ICON) atmosphere model for a region including Germany, the Netherlands and parts of other surrounding countries. The retrieval algorithm is applied to the synthetic data and comparison to the known input trace gas concentrations yields the retrieval error due to 3D cloud effects.&#160;<br>In this study, we study NO2, which is a key tropospheric trace gas measured by TROPOMI and the future atmospheric Sentinels (S4 and S5). The work starts with a sensitivity study for the simulations with a simple 2D box cloud. The influence of cloud parameters (e.g., cloud top height, cloud optical thickness), observation geometry, and spatial resolution are studied, and the most significant dependences of retrieval biases are identified and investigated. Several approaches to correct the NO2 retrieval in the cloud shadow are explored and ultimately applied to both synthetic data with realistic 3D clouds and real observations.</p>

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Improvement of stratospheric aerosol extinction retrieval from OMPS/LP using a new aerosol model

Atmospheric Measurement Techniques ◽

10.5194/amt-11-6495-2018 ◽

2018 ◽

Vol 11 (12) ◽

pp. 6495-6509 ◽

Cited By ~ 10

Author(s):

Zhong Chen ◽

Pawan K. Bhartia ◽

Robert Loughman ◽

Peter Colarco ◽

Matthew DeLand

Keyword(s):

Size Distribution ◽

Gamma Function ◽

Spectral Dependence ◽

Stratospheric Aerosol ◽

Cumulative Distribution ◽

Aerosol Size Distribution ◽

Retrieval Algorithm ◽

Aerosol Extinction ◽

Aerosol Model ◽

The Impact

Abstract. The Ozone Mapping and Profiler Suite Limb Profiler (OMPS/LP) has been flying on the Suomi National Polar-orbiting Partnership (S-NPP) satellite since October 2011. It is designed to produce ozone and aerosol vertical profiles at ∼2 km vertical resolution over the entire sunlit globe. Aerosol extinction profiles are computed with Mie theory using radiances measured at 675 nm. The operational Version 1.0 (V1.0) aerosol extinction retrieval algorithm assumes a bimodal lognormal aerosol size distribution (ASD) whose parameters were derived by combining an in situ measurement of aerosol microphysics with the Stratospheric Aerosol and Gas Experiment (SAGE II) aerosol extinction climatology. Internal analysis indicates that this bimodal lognormal ASD does not sufficiently explain the spectral dependence of LP-measured radiances. In this paper we describe the derivation of an improved aerosol size distribution, designated Version 1.5 (V1.5), for the LP retrieval algorithm. The new ASD uses a gamma function distribution that is derived from Community Aerosol and Radiation Model for Atmospheres (CARMA)-calculated results. A cumulative distribution fit derived from the gamma function ASD gives better agreement with CARMA results at small particle radii than bimodal or unimodal functions. The new ASD also explains the spectral dependence of LP-measured radiances better than the V1.0 ASD. We find that the impact of our choice of ASD on the retrieved extinctions varies strongly with the underlying reflectivity of the scene. Initial comparisons with collocated extinction profiles retrieved at 676 nm from the SAGE III instrument on the International Space Station (ISS) show a significant improvement in agreement for the LP V1.5 retrievals. Zonal mean extinction profiles agree to within 10 % between 19 and 29 km, and regression fits of collocated samples show improved correlation and reduced scatter compared to the V1.0 product. This improved agreement will motivate development of more sophisticated ASDs from CARMA results that incorporate latitude, altitude and seasonal variations in aerosol properties.

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Sensitivity of formaldehyde (HCHO) column measurements from a geostationary satellite to aerosol temporal variation in East Asia

10.5194/acp-2016-712 ◽

2016 ◽

Author(s):

Hyeong-Ahn Kwon ◽

Rokjin J. Park ◽

Jaein I. Jeong ◽

Seungun Lee ◽

Gonzalo González Abad ◽

...

Keyword(s):

East Asia ◽

Temporal Variation ◽

Geostationary Satellite ◽

Dust Storms ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Observation System ◽

Transfer Model ◽

True Value ◽

The Impact

Abstract. We examine upcoming geostationary satellite observations of formaldehyde (HCHO) columns in East Asia and the retrieval sensitivity to the temporal variation of air mass factor (AMF) considering the presence of aerosols. Observation system simulation experiments (OSSE) were conducted using a combination of a global 3-D chemical transport model (GEOS-Chem), a radiative transfer model (VLIDORT), and a HCHO retrieval algorithm developed for Geostationary Environment Monitoring Spectrometer (GEMS), which will be launched in 2019. Application of the retrieval algorithm to simulated hourly radiances yields the retrieved HCHO column concentrations, which are then compared with the GEOS-Chem HCHO columns as a true value for the evaluation of the retrieval algorithm. In order to examine the retrieval sensitivity to the temporal variation of AMF, we compare the retrieved HCHO columns using monthly versus hourly AMF values and find that the HCHO vertical columns with hourly AMF are in better agreement with the true values, relative to those with monthly AMF. The differences between hourly and monthly AMF range from −0.70 to 0.73 in absolute value and are mainly caused by temporal changes of aerosol chemical composition: scattering aerosol enhances AMF, whereas absorbing aerosol reduces it. The temporal variations of AMF caused by aerosols increase and decrease HCHO VCDs by 84 % and 34 %, respectively, compared to HCHO VCDs using monthly AMF. We apply our calculated AMF with the aerosol effects to OMI HCHO products in March, 2006 when Asian dust storms occurred and find −18 %–33 % changes in the retrieved HCHO columns in East Asia. The impact of aerosols cannot be neglected for future geostationary observations.

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The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 Aerosol Extinction Retrieval Algorithm: Theoretical Basis

10.5194/amt-2017-299 ◽

2017 ◽

Cited By ~ 4

Author(s):

Robert Loughman ◽

Pawan K. Bhartia ◽

Zhong Chen ◽

Philippe Xu ◽

Ernest Nyaku ◽

...

Keyword(s):

Spherical Shell ◽

Theoretical Basis ◽

Relaxation Method ◽

Radiative Transfer Model ◽

Aerosol Size Distribution ◽

Retrieval Algorithm ◽

Transfer Model ◽

Aerosol Extinction ◽

Log Normal ◽

Horizontal Variations

Abstract. The theoretical basis of the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 aerosol extinction (AE) retrieval algorithm is presented. The algorithm uses an assumed bi-modal log-normal aerosol size distribution to retrieve AE profiles at 675 nm from OMPS LP radiance measurements. A first-guess AE profile is updated by iteration using the Chahine non-linear relaxation method, based on comparisons between the measured radiance profile at 675 nm and the radiance profile calculated by the Gauss-Seidel Limb Scattering (GSLS) radiative transfer model for a spherical-shell atmosphere. This algorithm is discussed in the context of previous limb-scattering AE retrieval algorithms, and the most significant error sources are enumerated. The retrieval algorithm is limited primarily by uncertainty about the aerosol phase function, and by horizontal variations in aerosol extinction, which violate the spherical-shell atmosphere assumed in the Version 1 algorithm.

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Improvement of stratospheric aerosol extinction retrieval from OMPS/LP using a new aerosol model

10.5194/amt-2018-221 ◽

2018 ◽

Cited By ~ 1

Author(s):

Zhong Chen ◽

Pawan K. Bhartia ◽

Robert Loughman ◽

Peter Colarco ◽

Matthew DeLand

Keyword(s):

Size Distribution ◽

Gamma Function ◽

Spectral Dependence ◽

Stratospheric Aerosol ◽

Cumulative Distribution ◽

Aerosol Size Distribution ◽

Retrieval Algorithm ◽

Aerosol Extinction ◽

Aerosol Model ◽

The Impact

Abstract. The Ozone Mapping and Profiler Suite Limb Profiler (OMPS/LP) has been flying on the Suomi NPP satellite since October 2011. It is designed to produce ozone and aerosol vertical profiles at ~2 km vertical resolution over the entire sunlit globe. Aerosol extinction profiles are computed with Mie theory using radiances measured at 675 nm. The operational Version 1.0 (V1.0) aerosol extinction retrieval algorithm assumes a bimodal lognormal aerosol size distribution (ASD) whose parameters were derived by combining an in situ measurement of aerosol microphysics with the SAGE II aerosol extinction climatology. Internal analysis indicates that this bimodal lognormal ASD does not sufficiently explain the spectral dependence of LP measured radiances. In this paper we describe the derivation of an improved aerosol size distribution, designated Version 1.5 (V1.5), for the LP retrieval algorithm. The new ASD uses a gamma function distribution that is derived from Community Aerosol and Radiation Model for Atmospheres (CARMA) calculated results. A cumulative distribution fit derived from the gamma function ASD gives better agreement with CARMA results at small particle radii than bimodal or unimodal functions. The new ASD also explains the spectral dependence of LP measured radiances better than the V1.0 ASD. We find that the impact of our choice of ASD on the retrieved extinctions varies strongly with the underlying reflectivity of the scene. Initial comparisons with co-located extinction profiles retrieved at 676 nm from the SAGE III/ISS instrument show a significant improvement in agreement for the LP V1.5 retrievals. Zonal mean extinction profiles agree to within 10 % between 19–29 km, and regression fits of collocated samples show improved correlation and reduced scatter compared to the V1.0 product. This improved agreement will motivate development of more sophisticated ASDs from CARMA results that incorporate latitude, altitude, and seasonal variations in aerosol properties.

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Quantifying the impact of aerosol scattering on the retrieval of methane from airborne remote sensing measurements

10.5194/amt-2020-51 ◽

2020 ◽

Author(s):

Yunxia Huang ◽

Vijay Natraj ◽

Zhaocheng Zeng ◽

Yuk L. Yung

Keyword(s):

Remote Sensing ◽

Infrared Imaging ◽

Matched Filter ◽

Optimal Estimation ◽

Radiative Transfer Model ◽

Transfer Model ◽

Atmospheric Methane ◽

Ch4 Emissions ◽

Aerosol Scattering ◽

The Impact

Abstract. As a greenhouse gas with strong global warming potential, atmospheric methane (CH4) emissions have attracted a great deal of attention. Remote sensing measurements can provide information about CH4 sources and emissions. However, accurate assessment of CH4 emissions is challenging due to the influence of aerosol scattering in the atmosphere. In this study, imaging spectroscopic measurements from the Airborne Visible/Infrared Imaging Spectrometer–Next Generation (AVIRIS-NG) in the short-wave infrared are used to analyze the impact of aerosol scattering on CH4 retrievals. Using a numerically efficient two-stream-exact-single-scattering radiative transfer model, we also simulate AVIRIS-NG measurements for different scenarios and quantify the impact of aerosol scattering using two retrieval techniques – the traditional Matched Filter (MF) method and the Optimal Estimation (OE) method, which is a popular approach for trace gas retrievals. The results show that the MF method exhibits up to 50 % lower fractional retrieval bias compared to the OE method at high CH4 concentrations (> 100 % enhancement over typical background values) and is suitable for detecting strong CH4 emissions, while the OE method is an optimal technique for diffuse sources (

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Quantification and mitigation of the impact of scene inhomogeneity on Sentinel-4 UVN UV-VIS retrievals

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-2043-2012 ◽

2012 ◽

Vol 5 (2) ◽

pp. 2043-2075

Author(s):

S. Noël ◽

K. Bramstedt ◽

H. Bovensmann ◽

J. P. Burrows ◽

C. Standfuss ◽

...

Keyword(s):

Optimal Estimation ◽

Maximum Error ◽

The Other ◽

Radiative Transfer Model ◽

Transfer Model ◽

Imaging Spectrometer ◽

Wavelength Calibration ◽

Data Products ◽

Tropospheric O3 ◽

The Impact

Abstract. The quality of trace gas products derived from measurements of a space-borne imaging spectrometer is affected by the inhomogeneity of the illumination of the instrument slit and thus by the heterogeneity of the observed scene. This paper aims to quantify this effect and summarise findings on how to mitigate the impact of inhomogeneous slit illumination on tropospheric O3, NO2, SO2 and HCHO columns derived from measurements of the Sentinel-4 UVN imaging spectrometer. For this purpose, spectra for inhomogeneous ground scenes have been simulated based on a combination of a radiative transfer model and spatially high resolved MODIS (Moderate Resolution Imaging Spectroradiometer) data. The resulting errors on tropospheric O3, NO2, SO2 and HCHO columns derived from these spectra have been determined via an optimal estimation approach. It could be concluded that inhomogeneous illumination results in significant errors in the data products if the natural inhomogeneity of the observed scenes is not accounted for. O3 columns are less affected than the other data products; largest errors occur for NO2 (mean absolute errors about 5%, maximum error exceeding 50%). These errors may be significantly reduced (by factors up to >10) by an appropriate wavelength calibration applied individually to each Earthshine radiance spectrum. With wavelength calibration the estimated mean absolute errors due to inhomogeneity are for all gases well below 1%; maximum errors are about 10% for NO2 and around 5% for the other gases.

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