scholarly journals Updated SAO OMI formaldehyde retrieval

2014 ◽  
Vol 7 (1) ◽  
pp. 1-31 ◽  
Author(s):  
G. González Abad ◽  
X. Liu ◽  
K. Chance ◽  
H. Wang ◽  
T. P. Kurosu ◽  
...  
Keyword(s):  
Theoretical Basis ◽  
Retrieval Algorithm ◽  
Reference Spectrum ◽  
Ozone Monitoring Instrument ◽  
High Concentration ◽  
Air Mass ◽  
Mass Factor ◽  
Ozone Monitoring ◽  
Collisional Complex ◽  
Level 2

Abstract. We present and discuss the Smithsonian Astrophysical Observatory (SAO) formaldehyde (H2CO) retrieval algorithm for the Ozone Monitoring Instrument (OMI) which is the operational retrieval for NASA OMI H2CO. The version of the algorithm described here includes relevant changes with respect to the operational one, including differences in the reference spectra for H2CO, the fit of O2-O2 collisional complex, updates in the high resolution solar reference spectrum, the use of a model reference sector over the remote Pacific Ocean to normalize the retrievals, an updated Air Mass Factor (AMF) calculation scheme, and the inclusion of scattering weights and vertical H2CO profile in the level 2 products. The theoretical basis of the retrieval is discussed in detail. Typical values for retrieved vertical columns are between 4 × 1015 and 4 × 1016 molecules cm−2 with typical fitting uncertainties ranging between 40% and 100%. In high concentration regions the errors are usually reduced to 30%. The detection limit is estimated at 3 × 1015 molecules cm−2. These updated retrievals are compared with previous ones.

scholarly journals Updated Smithsonian Astrophysical Observatory Ozone Monitoring Instrument (SAO OMI) formaldehyde retrieval

2015 ◽  
Vol 8 (1) ◽  
pp. 19-32 ◽  
Author(s):  
G. González Abad ◽  
X. Liu ◽  
K. Chance ◽  
H. Wang ◽  
T. P. Kurosu ◽  
...  
Keyword(s):  
Temporal Stability ◽  
Cloud Fraction ◽  
Retrieval Algorithm ◽  
Reference Spectrum ◽  
Ozone Monitoring Instrument ◽  
High Concentration ◽  
Monitoring Instrument ◽  
Mass Factor ◽  
Ozone Monitoring ◽  
Level 2

Abstract. We present and discuss the Smithsonian Astrophysical Observatory (SAO) formaldehyde (H2CO) retrieval algorithm for the Ozone Monitoring Instrument (OMI) which is the operational retrieval for NASA OMI H2CO. The version of the algorithm described here includes relevant changes with respect to the operational one, including differences in the reference spectra for H2CO, the fit of O2–O2 collisional complex, updates in the high-resolution solar reference spectrum, the use of a model reference sector over the remote Pacific Ocean to normalize the retrievals, an updated air mass factor (AMF) calculation scheme, and the inclusion of scattering weights and vertical H2CO profile in the level 2 products. The setup of the retrieval is discussed in detail. We compare the results of the updated retrieval with the results from the previous SAO H2CO retrieval. The improvement in the slant column fit increases the temporal stability of the retrieval and slightly reduces the noise. The change in the AMF calculation has increased the AMFs by 20%, mainly due to the consideration of the radiative cloud fraction. Typical values for retrieved vertical columns are between 4 × 1015 and 4 × 1016 molecules cm−2, with typical fitting uncertainties ranging between 45 and 100%. In high-concentration regions the errors are usually reduced to 30%. The detection limit is estimated at 1 × 1016 molecules cm−2.

scholarly journals An improved tropospheric NO<sub>2</sub> column retrieval algorithm for the Ozone Monitoring Instrument

2011 ◽  
Vol 4 (9) ◽  
pp. 1905-1928 ◽  
Author(s):  
K. F. Boersma ◽  
H. J. Eskes ◽  
R. J. Dirksen ◽  
R. J. van der A ◽  
J. P. Veefkind ◽  
...  
Keyword(s):  
High Resolution ◽  
Surface Albedo ◽  
Retrieval Algorithm ◽  
Ozone Monitoring Instrument ◽  
Air Mass ◽  
Monitoring Instrument ◽  
Tropospheric No2 ◽  
Mass Factor ◽  
Ozone Monitoring ◽  
The Impact

Abstract. We present an improved tropospheric nitrogen dioxide column retrieval algorithm (DOMINO v2.0) for OMI based on better air mass factors (AMFs) and a correction for across-track stripes resulting from calibration errors in the OMI backscattered reflectances. Since October 2004, NO2 retrievals from the Ozone Monitoring Instrument (OMI), a UV/Vis nadir spectrometer onboard NASA's EOS-Aura satellite, have been used with success in several scientific studies focusing on air quality monitoring, detection of trends, and NOx emission estimates. Dedicated evaluations of previous DOMINO tropospheric NO2 retrievals indicated their good quality, but also suggested that the tropospheric columns were susceptible to high biases (by 0–40%), probably because of errors in the air mass factor calculations. Here we update the DOMINO air mass factor approach. We calculate a new look-up table (LUT) for altitude-dependent AMFs based on more realistic atmospheric profile parameters, and include more surface albedo and surface pressure reference points than before. We improve the sampling of the TM4 model, resulting in a priori NO2 profiles that are better mixed throughout the boundary layer. We evaluate the NO2 profiles simulated with the improved TM4 sampling as used in the AMF calculations and show that they are highly consistent with in situ NO2 measurements from aircraft during the INTEX-A and INTEX-B campaigns in 2004 and 2006. Our air mass factor calculations are further updated by the implementation of a high-resolution terrain height and a high-resolution surface albedo climatology based on OMI measurements. Together with a correction for across-track stripes, the overall impact of the improved terrain height and albedo descriptions is modest (<5%) on average over large polluted areas, but still causes significant changes locally. The main changes in the DOMINO v2.0 algorithm follow from the new LUT and the improved TM4 sampling that results in more NO2 simulated aloft, where sensitivity to NO2 is higher, and amount to reductions in tropospheric NO2 columns of up to 20% in winter, and 10% in summer over extended polluted areas. We investigate the impact of aerosols on the NO2 retrieval, and based on a comparison of concurrent retrievals of clouds from OMI and aerosols from MODIS Aqua, we find empirical evidence that OMI cloud retrievals are sensitive to the presence of scattering aerosols. It follows that an implicit correction for the effects of aerosols occurs through the aerosol-induced cloud parameters in DOMINO, and we show that such an empirical correction amounts to a 20 %AMF reduction in summer and ±10% changes in winter over the eastern United States.

scholarly journals An improved tropospheric NO<sub>2</sub> column retrieval algorithm for the Ozone Monitoring Instrument

2011 ◽  
Vol 4 (2) ◽  
pp. 2329-2388 ◽  
Author(s):  
K. F. Boersma ◽  
H. J. Eskes ◽  
R. J. Dirksen ◽  
R. J. van der A ◽  
J. P. Veefkind ◽  
...  
Keyword(s):  
High Resolution ◽  
Surface Albedo ◽  
Retrieval Algorithm ◽  
Ozone Monitoring Instrument ◽  
Air Mass ◽  
Monitoring Instrument ◽  
Tropospheric No2 ◽  
Mass Factor ◽  
Ozone Monitoring ◽  
The Impact

Abstract. We present an improved tropospheric nitrogen dioxide column retrieval algorithm (DOMINO v2.0) for OMI based on better air mass factors (AMFs) and a correction for across-track stripes resulting from calibration errors in the OMI backscattered reflectances. Since October 2004, NO2 retrievals from the Ozone Monitoring Instrument (OMI), a UV/Vis nadir spectrometer onboard NASA's EOS-Aura satellite, have been used with success in several scientific studies focusing on air quality monitoring, detection of trends, and NOx emission estimates. Dedicated evaluations of previous DOMINO tropospheric NO2 retrievals indicated their good quality, but also suggested that the tropospheric columns were susceptible to high biases (by 0–40%), probably because of errors in the air mass factor calculations. Here we update the DOMINO air mass factor approach. We calculate a new look-up table (LUT) for altitude-dependent AMFs based on more realistic atmospheric profile parameters, and include more surface albedo and surface pressure reference points than before. We improve the sampling of the TM4 model, resulting in a priori NO2 profiles that are better mixed throughout the boundary layer. We evaluate the NO2 profiles simulated with the improved TM4 sampling as used in the AMF calculations and show that they are highly consistent with in situ NO2 measurements from aircraft during the INTEX-A and INTEX-B campaigns in 2004 and 2006. Our air mass factor calculations are further updated by the implementation of a high-resolution terrain height and a high-resolution surface albedo climatology based on OMI measurements. Together with a correction for across-track stripes, the overall impact of the improved terrain height and albedo descriptions is modest (<5%) on average over large polluted areas, but still causes significant changes locally. The main changes in the DOMINO v2.0 algorithm follow from the new LUT and the improved TM4 sampling that results in more NO2 simulated aloft, where sensitivity to NO2 is higher, and amount to reductions in tropospheric NO2 columns of up to 20% in winter, and 10% in summer over extended polluted areas. We investigate the impact of aerosols on the NO2 retrieval, and based on a comparison of concurrent retrievals of clouds from OMI and aerosols from MODIS Aqua, we find empirical evidence that OMI cloud retrievals are sensitive to the presence of scattering aerosols. It follows that an implicit correction for the effects of aerosols occurs through the aerosol-induced cloud parameters in DOMINO, and we show that such a correction amounts to a 20% AMF reduction in summer and ±10% changes in winter over the eastern US.

scholarly journals Validation of OMI, GOME-2A and GOME-2B tropospheric NO<sub>2</sub>, SO<sub>2</sub> and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products

2017 ◽  
Vol 17 (8) ◽  
pp. 5007-5033 ◽  
Author(s):  
Yang Wang ◽  
Steffen Beirle ◽  
Johannes Lampel ◽  
Mariliza Koukouli ◽  
Isabelle De Smedt ◽  
...  
Keyword(s):  
Cloud Fraction ◽  
Satellite Observations ◽  
Data Sets ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Air Mass ◽  
Clear Sky ◽  
Satellite Retrievals ◽  
Mass Factor ◽  
Ozone Monitoring

Abstract. Tropospheric vertical column densities (VCDs) of NO2, SO2 and HCHO derived from the Ozone Monitoring Instrument (OMI) on AURA and the Global Ozone Monitoring Experiment 2 aboard METOP-A (GOME-2A) and METOP-B (GOME-2B) are widely used to characterize the global distributions, trends and dominating sources of these trace gases. They are also useful for the comparison with chemical transport models (CTMs). We use tropospheric VCDs and vertical profiles of NO2, SO2 and HCHO derived from MAX-DOAS measurements from 2011 to 2014 in Wuxi, China, to validate the corresponding products (daily and bi-monthly-averaged data) derived from OMI and GOME-2A/B by different scientific teams. Prior to the comparison, the spatial and temporal coincidence criteria for MAX-DOAS and satellite data are determined by a sensitivity study using different spatial and temporal averaging conditions. Cloud effects on both MAX-DOAS and satellite observations are also investigated. Our results indicate that the discrepancies between satellite and MAX-DOAS results increase with increasing effective cloud fraction and are dominated by the effects of clouds on the satellite products. In comparison with MAX-DOAS, we found a systematic underestimation of all SO2 (40 to 57 %) and HCHO products (about 20 %), and an overestimation of the GOME-2A/B NO2 products (about 30 %), but good consistency with the DOMINO version 2 NO2 product. To better understand the reasons for these differences, we evaluated the a priori profile shapes used in the OMI retrievals (derived from CTM) by comparison with those derived from the MAX-DOAS observations. Significant differences are found for the SO2 and HCHO profile shapes derived from the IMAGES model, whereas on average good agreement is found for the NO2 profile shapes derived from the TM4 model. We also applied the MAX-DOAS profile shapes to the satellite retrievals and found that these modified satellite VCDs agree better with the MAX-DOAS VCDs than the VCDs from the original data sets by up to 10, 47 and 35 % for NO2, SO2 and HCHO, respectively. Furthermore, we investigated the effect of aerosols on the satellite retrievals. For OMI observations of NO2, a systematic underestimation is found for large AOD, which is mainly attributed to effect of the aerosols on the cloud retrieval and the subsequent application of a cloud correction scheme (implicit aerosol correction). In contrast, the effect of aerosols on the clear-sky air mass factor (explicit aerosol correction) has a smaller effect. For SO2 and HCHO observations selected in the same way, no clear aerosol effect is found, probably because for the considered data sets no cloud correction is applied (and also because of the larger scatter). From our findings we conclude that for satellite observations with cloud top pressure (CTP) > 900 hPa and effective cloud fraction (eCF) < 10 % the application of a clear-sky air mass factor might be a good option if accurate aerosol information is not available. Another finding of our study is that the ratio of morning-to-afternoon NO2 VCDs can be considerably overestimated if results from different sensors and/or retrievals (e.g. OMI and GOME-2) are used, whereas fewer deviations for HCHO and SO2 VCDs are found.

scholarly journals Retrievals of Tropospheric Ozone Profiles from the Synergic Observation of AIRS and OMI: Methodology and Validation

2018 ◽  
Author(s):  
Dejian Fu ◽  
Susan S. Kulawik ◽  
Kazuyuki Miyazaki ◽  
Kevin W. Bowman ◽  
John R. Worden ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Measurement Uncertainty ◽  
Tropospheric Ozone ◽  
Retrieval Algorithm ◽  
Vertical Resolution ◽  
Ozone Monitoring Instrument ◽  
Atmospheric Infrared Sounder ◽  
Global Coverage ◽  
Ozone Monitoring ◽  
Wide Swath

Abstract. The Tropospheric Emission Spectrometer (TES) on the A-Train Aura satellite was designed to profile tropospheric ozone and its precursors, taking measurements from 2004 to 2018. Starting in 2008, TES global sampling of tropospheric ozone was gradually reduced in latitude with global coverage stopping in 2011. To extend the record of TES, this work presents a multispectral approach that will provide O3 data products with vertical resolution and measurement uncertainty similar to TES by combining the single-footprint thermal infrared (TIR) hyperspectral radiances from the Aqua Atmospheric Infrared Sounder (AIRS) instrument and the ultraviolet (UV) channels from the Aura Ozone Monitoring Instrument (OMI). The joint AIR+OMI O3 retrievals are processed through the MUlti-SpEctra, MUlti-SpEcies, MUlti-SEnsors (MUSES) retrieval algorithm. Comparisons of collocated joint AIRS+OMI and TES to ozonesonde measurements show that both systems have similar errors, with mean and standard deviation of the differences well within the estimated measurement uncertainty. AIRS+OMI and TES have slightly different biases (within 5 parts per billion) versus the sondes. Both AIRS and OMI have wide swath widths (~ 1,650 km for AIRS; ~ 2,600 km for OMI) across satellite ground tracks. Consequently, the joint AIRS+OMI measurements have the potential to maintain TES vertical sensitivity while increasing coverage by two orders of magnitude, thus providing an unprecedented new dataset to quantify the evolution of tropospheric ozone.

scholarly journals Structural uncertainty in air mass factor calculation for NO<sub>2</sub> and HCHO satellite retrievals

2017 ◽  
Vol 10 (3) ◽  
pp. 759-782 ◽  
Author(s):  
Alba Lorente ◽  
K. Folkert Boersma ◽  
Huan Yu ◽  
Steffen Dörner ◽  
Andreas Hilboll ◽  
...  
Keyword(s):  
Surface Albedo ◽  
Trace Gas ◽  
Retrieval Algorithm ◽  
Structural Uncertainty ◽  
Ancillary Data ◽  
Air Mass ◽  
Cloud Parameters ◽  
Uncertainty Estimates ◽  
Satellite Retrievals ◽  
Mass Factor

Abstract. Air mass factor (AMF) calculation is the largest source of uncertainty in NO2 and HCHO satellite retrievals in situations with enhanced trace gas concentrations in the lower troposphere. Structural uncertainty arises when different retrieval methodologies are applied within the scientific community to the same satellite observations. Here, we address the issue of AMF structural uncertainty via a detailed comparison of AMF calculation methods that are structurally different between seven retrieval groups for measurements from the Ozone Monitoring Instrument (OMI). We estimate the escalation of structural uncertainty in every sub-step of the AMF calculation process. This goes beyond the algorithm uncertainty estimates provided in state-of-the-art retrievals, which address the theoretical propagation of uncertainties for one particular retrieval algorithm only. We find that top-of-atmosphere reflectances simulated by four radiative transfer models (RTMs) (DAK, McArtim, SCIATRAN and VLIDORT) agree within 1.5 %. We find that different retrieval groups agree well in the calculations of altitude resolved AMFs from different RTMs (to within 3 %), and in the tropospheric AMFs (to within 6 %) as long as identical ancillary data (surface albedo, terrain height, cloud parameters and trace gas profile) and cloud and aerosol correction procedures are being used. Structural uncertainty increases sharply when retrieval groups use their preference for ancillary data, cloud and aerosol correction. On average, we estimate the AMF structural uncertainty to be 42 % over polluted regions and 31 % over unpolluted regions, mostly driven by substantial differences in the a priori trace gas profiles, surface albedo and cloud parameters. Sensitivity studies for one particular algorithm indicate that different cloud correction approaches result in substantial AMF differences in polluted conditions (5 to 40 % depending on cloud fraction and cloud pressure, and 11 % on average) even for low cloud fractions (<  0.2) and the choice of aerosol correction introduces an average uncertainty of 50 % for situations with high pollution and high aerosol loading. Our work shows that structural uncertainty in AMF calculations is significant and that it is mainly caused by the assumptions and choices made to represent the state of the atmosphere. In order to decide which approach and which ancillary data are best for AMF calculations, we call for well-designed validation exercises focusing on polluted conditions in which AMF structural uncertainty has the highest impact on NO2 and HCHO retrievals.

scholarly journals Ozone Monitoring Instrument (OMI) Aura nitrogen dioxide standard product version 4.0 with improved surface and cloud treatments

2021 ◽  
Vol 14 (1) ◽  
pp. 455-479
Author(s):  
Lok N. Lamsal ◽  
Nickolay A. Krotkov ◽  
Alexander Vasilkov ◽  
Sergey Marchenko ◽  
Wenhan Qin ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Retrieval Algorithm ◽  
Data Sets ◽  
Ozone Monitoring Instrument ◽  
Monitoring Instrument ◽  
Standard Product ◽  
Independent Observations ◽  
Moderate Resolution ◽  
Ozone Monitoring ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. We present a new and improved version (V4.0) of the NASA standard nitrogen dioxide (NO2) product from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This version incorporates the most salient improvements for OMI NO2 products suggested by expert users and enhances the NO2 data quality in several ways through improvements to the air mass factors (AMFs) used in the retrieval algorithm. The algorithm is based on the geometry-dependent surface Lambertian equivalent reflectivity (GLER) operational product that is available on an OMI pixel basis. GLER is calculated using the vector linearized discrete ordinate radiative transfer (VLIDORT) model, which uses as input high-resolution bidirectional reflectance distribution function (BRDF) information from NASA's Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) instruments over land and the wind-dependent Cox–Munk wave-facet slope distribution over water, the latter with a contribution from the water-leaving radiance. The GLER combined with consistently retrieved oxygen dimer (O2–O2) absorption-based effective cloud fraction (ECF) and optical centroid pressure (OCP) provide improved information to the new NO2 AMF calculations. The new AMFs increase the retrieved tropospheric NO2 by up to 50 % in highly polluted areas; these differences arise from both cloud and surface BRDF effects as well as biases between the new MODIS-based and previously used OMI-based climatological surface reflectance data sets. We quantitatively evaluate the new NO2 product using independent observations from ground-based and airborne instruments. The new V4.0 data and relevant explanatory documentation are publicly available from the NASA Goddard Earth Sciences Data and Information Services Center (https://disc.gsfc.nasa.gov/datasets/OMNO2_V003/summary/, last access: 8 November 2020), and we encourage their use over previous versions of OMI NO2 products.

scholarly journals The High-Resolution Solar Reference Spectrum between 250 and 550 nm and its Application to Measurements with the Ozone Monitoring Instrument

Solar Physics ◽  
2008 ◽  
Vol 249 (2) ◽  
pp. 281-291 ◽  
Author(s):  
Marcel Dobber ◽  
Robert Voors ◽  
Ruud Dirksen ◽  
Quintus Kleipool ◽  
Pieternel Levelt
Keyword(s):  
High Resolution ◽  
Reference Spectrum ◽  
Ozone Monitoring Instrument ◽  
Monitoring Instrument ◽  
Ozone Monitoring

scholarly journals Retrievals of tropospheric ozone profiles from the synergism of AIRS and OMI: methodology and validation

2018 ◽  
Vol 11 (10) ◽  
pp. 5587-5605 ◽  
Author(s):  
Dejian Fu ◽  
Susan S. Kulawik ◽  
Kazuyuki Miyazaki ◽  
Kevin W. Bowman ◽  
John R. Worden ◽  
...  
Keyword(s):  
Measurement Error ◽  
Tropospheric Ozone ◽  
Retrieval Algorithm ◽  
Vertical Resolution ◽  
Ozone Monitoring Instrument ◽  
Atmospheric Infrared Sounder ◽  
Data Set ◽  
Global Coverage ◽  
Ozone Monitoring ◽  
Wide Swath

Abstract. The Tropospheric Emission Spectrometer (TES) on the A-Train Aura satellite was designed to profile tropospheric ozone and its precursors, taking measurements from 2004 to 2018. Starting in 2008, TES global sampling of tropospheric ozone was gradually reduced in latitude, with global coverage stopping in 2011. To extend the record of TES, this work presents a multispectral approach that will provide O3 data products with vertical resolution and measurement error similar to TES by combining the single-footprint thermal infrared (TIR) hyperspectral radiances from the Aqua Atmospheric Infrared Sounder (AIRS) instrument and the ultraviolet (UV) channels from the Aura Ozone Monitoring Instrument (OMI). The joint AIRS+OMI O3 retrievals are processed through the MUlti-SpEctra, MUlti-SpEcies, MUlti-SEnsors (MUSES) retrieval algorithm. Comparisons of collocated joint AIRS+OMI and TES to ozonesonde measurements show that both systems have similar errors, with mean and standard deviation of the differences well within the estimated measurement error. AIRS+OMI and TES have slightly different biases (within 5 parts per billion) vs. the sondes. Both AIRS and OMI have wide swath widths (∼1650 km for AIRS; ∼2600 km for OMI) across satellite ground tracks. Consequently, the joint AIRS+OMI measurements have the potential to maintain TES vertical sensitivity while increasing coverage by 2 orders of magnitude, thus providing an unprecedented new data set with which to quantify the evolution of tropospheric ozone.

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