scholarly journals Retrieval of tropospheric NO<sub>2</sub> using the MAX-DOAS method combined with relative intensity measurements for aerosol correction

2010 ◽  
Vol 3 (5) ◽  
pp. 1287-1305 ◽  
Author(s):  
T. Vlemmix ◽  
A. J. M. Piters ◽  
P. Stammes ◽  
P. Wang ◽  
P. F. Levelt
Keyword(s):  
Boundary Layer ◽  
Relative Intensity ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Data Set ◽  
Intensity Measurements ◽  
Significant Difference ◽  
Tropospheric No2 ◽  
Retrieval Scheme ◽  
Sky Radiance

Abstract. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a technique to measure trace gas amounts in the lower troposphere from ground-based scattered sunlight observations. MAX-DOAS observations are especially suitable for validation of tropospheric trace gas observations from satellite, since they have a representative range of several kilometers, both in the horizontal and in the vertical dimension. A two-step retrieval scheme is presented here, to derive aerosol corrected tropospheric NO2 columns from MAX-DOAS observations. In a first step, boundary layer aerosols, characterized in terms of aerosol optical thickness (AOT), are estimated from relative intensity observations, which are defined as the ratio of the sky radiance at elevation α and the sky radiance in the zenith. Relative intensity measurements have the advantage of a strong dependence on boundary layer AOT and almost no dependence on boundary layer height. In a second step, tropospheric NO2 columns are derived from differential slant columns, based on AOT-dependent air mass factors. This two-step retrieval scheme was applied to cloud free periods in a twelve month data set of observations in De Bilt, The Netherlands. In a comparison with AERONET (Cabauw site) a mean difference in AOT (AERONET minus MAX-DOAS) of −0.01±0.08 was found, and a correlation of 0.85. Tropospheric-NO2 columns were compared with OMI-satellite tropospheric NO2. For ground-based observations restricted to uncertainties below 10%, no significant difference was found, and a correlation of 0.88.

scholarly journals Retrieval of tropospheric NO2</sub> using the MAX-DOAS method combined with relative intensity measurements for aerosol correction

2010 ◽  
Vol 3 (3) ◽  
pp. 2317-2366 ◽  
Author(s):  
T. Vlemmix ◽  
A. J. M. Piters ◽  
P. Stammes ◽  
P. Wang ◽  
P. F. Levelt
Keyword(s):  
Boundary Layer ◽  
Relative Intensity ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Data Set ◽  
Intensity Measurements ◽  
Significant Difference ◽  
Tropospheric No2 ◽  
Retrieval Scheme ◽  
Sky Radiance

Abstract. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a technique to measure trace gas amounts in the lower troposphere from ground-based scattered sunlight observations. MAX-DOAS observations are especially suitable for validation of tropospheric trace gas observations from satellite, since they have a representative range of several kilometers, both in the horizontal and in the vertical dimension. A two-step retrieval scheme is presented here, to derive aerosol corrected tropospheric NO2 columns from MAX-DOAS observations. In a first step, boundary layer aerosols, characterized in terms of aerosol optical thickness (AOT), are estimated from relative intensity observations, which are defined as the ratio of the sky radiance at elevation α and the sky radiance in the zenith. Relative intensity measurements have the advantage of a strong dependence on boundary layer AOT and almost no dependence on boundary layer height. In a second step, tropospheric NO2 columns are derived from differential slant columns, based on AOT-dependent air mass factors. This two-step retrieval scheme was applied to cloud free periods in a twelve month data set of observations in De Bilt, the Netherlands. In a comparison with AERONET (Cabauw site) a mean difference in AOT (AERONET minus MAX-DOAS) of −0.01±0.08 was found, and a correlation of 0.85. Tropospheric-NO2 columns were compared with OMI-satellite tropospheric NO2. For ground-based observations restricted to uncertainties below 10%, no significant difference was found, and a correlation of 0.88.

scholarly journals MAX-DOAS tropospheric nitrogen dioxide column measurements compared with the Lotos-Euros air quality model

2015 ◽  
Vol 15 (3) ◽  
pp. 1313-1330 ◽  
Author(s):  
T. Vlemmix ◽  
H. J. Eskes ◽  
A. J. M. Piters ◽  
M. Schaap ◽  
F. J. Sauter ◽  
...  
Keyword(s):  
Air Quality ◽  
Urban Region ◽  
Optical Absorption Spectroscopy ◽  
Air Quality Model ◽  
Quality Model ◽  
Data Set ◽  
Weekly Cycle ◽  
Significant Difference ◽  
Tropospheric No2 ◽  
Long Time

Abstract. A 14-month data set of MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) tropospheric NO2 column observations in De Bilt, the Netherlands, has been compared with the regional air quality model Lotos-Euros. The model was run on a 7×7 km2 grid, the same resolution as the emission inventory used. A study was performed to assess the effect of clouds on the retrieval accuracy of the MAX-DOAS observations. Good agreement was found between modeled and measured tropospheric NO2 columns, with an average difference of less than 1% of the average tropospheric column (14.5 · 1015 molec cm−2). The comparisons show little cloud cover dependence after cloud corrections for which ceilometer data were used. Hourly differences between observations and model show a Gaussian behavior with a standard deviation (σ) of 5.5 · 1015 molec cm−2. For daily averages of tropospheric NO2 columns, a correlation of 0.72 was found for all observations, and 0.79 for cloud free conditions. The measured and modeled tropospheric NO2 columns have an almost identical distribution over the wind direction. A significant difference between model and measurements was found for the average weekly cycle, which shows a much stronger decrease during the weekend for the observations; for the diurnal cycle, the observed range is about twice as large as the modeled range. The results of the comparison demonstrate that averaged over a long time period, the tropospheric NO2 column observations are representative for a large spatial area despite the fact that they were obtained in an urban region. This makes the MAX-DOAS technique especially suitable for validation of satellite observations and air quality models in urban regions.

Intercomparison of Cloud Products based on S5P/TROPOMI Level 1b Data Version 1 and the updated Version 2

2021 ◽  
Author(s):  
Miriam Latsch ◽  
Andreas Richter ◽  
John P. Burrows ◽  
Thomas Wagner ◽  
Holger Sihler ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Recognition Algorithm ◽  
Cloud Fraction ◽  
Trace Gas ◽  
Oxygen Absorption ◽  
Data Sets ◽  
Absorption Bands ◽  
Data Set ◽  
Trace Species ◽  
Retrieval Scheme

&lt;p&gt;The first European Sentinel satellite for monitoring the composition of the Earth&amp;#8217;s atmosphere, the Sentinel 5 Precursor (S5p), carries the TROPOspheric Monitoring Instrument (TROPOMI) to map trace species of the global atmosphere at high spatial resolution. Retrievals of tropospheric trace gas columns from satellite measurements are strongly influenced by clouds. Thus, cloud retrieval algorithms were developed and implemented in the trace gas processing chain to consider this impact.&lt;/p&gt;&lt;p&gt;In this study, different cloud products available for NO&lt;sub&gt;2&lt;/sub&gt; retrievals based on the TROPOMI level 1b data version 1 and an updated TROPOMI level 1b test data set of version 2 (Diagnostic Data Set 2B, DDS2B) are analyzed. The data sets include a) the TROPOMI level 2 OCRA/ROCINN (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks) cloud products CRB (cloud as reflecting boundaries) and CAL (clouds as layers), b) the FRESCO (Fast Retrieval Scheme for Clouds from Oxygen absorption bands) cloud product,&amp;#160; c) the cloud fraction from the NO&lt;sub&gt;2&lt;/sub&gt; fitting window, d) the VIIRS (Visible Infrared Imaging Radiometer Suite) cloud product, and e) the MICRU (Mainz Iterative Cloud Retrieval Utilities) cloud fraction. The cloud products are compared with regard to cloud fraction, cloud height, cloud albedo/optical thickness, flagging and quality indicators in all 4 seasons. In particular, the differences of the cloud products under difficult situations such as snow or ice cover and sun glint are investigated.&lt;/p&gt;&lt;p&gt;We present results of a statistical analysis on a limited data set comparing cloud products from the current and the upcoming lv2 data versions and their approaches. The aim of this study is to better understand TROPOMI cloud products and their quantitative impacts on trace gas retrievals.&lt;/p&gt;

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box averaged mixing ratios and vertical profiles

2012 ◽  
Vol 5 (5) ◽  
pp. 7641-7673 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) differential Slant Column Densities (dSCDs) into near-surface box averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, does not require a-priori assumptions about the trace gas vertical distribution and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by MAX-DOAS measurements at different elevation angles, and by LP-DOAS. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near surface emission. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way and emphasizes the need of vertically resolved measurements.

scholarly journals First estimates of global free-tropospheric NO<sub>2</sub> abundances derived using a cloud-slicing technique applied to satellite observations from the Aura Ozone Monitoring Instrument (OMI)

2014 ◽  
Vol 14 (19) ◽  
pp. 10565-10588 ◽  
Author(s):  
S. Choi ◽  
J. Joiner ◽  
Y. Choi ◽  
B. N. Duncan ◽  
A. Vasilkov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Profile Analysis ◽  
Middle Latitude ◽  
Optical Absorption Spectroscopy ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Monitoring Instrument ◽  
Single Orbit ◽  
Tropospheric No2 ◽  
Ozone Monitoring

Abstract. We derive free-tropospheric NO2 volume mixing ratios (VMRs) by applying a cloud-slicing technique to data from the Ozone Monitoring Instrument (OMI) on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO2 column versus the cloud scene pressure is proportional to the NO2 VMR. In this work, we use a sample of nearby OMI pixel data from a single orbit for the linear fit. The OMI data include cloud scene pressures from the rotational-Raman algorithm and above-cloud NO2 vertical column density (VCD) (defined as the NO2 column from the cloud scene pressure to the top of the atmosphere) from a differential optical absorption spectroscopy (DOAS) algorithm. We compare OMI-derived NO2 VMRs with in situ aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in 2006. The agreement is generally within the estimated uncertainties when appropriate data screening is applied. We then derive a global seasonal climatology of free-tropospheric NO2 VMR in cloudy conditions. Enhanced NO2 in the free troposphere commonly appears near polluted urban locations where NO2 produced in the boundary layer may be transported vertically out of the boundary layer and then horizontally away from the source. Signatures of lightning NO2 are also shown throughout low and middle latitude regions in summer months. A profile analysis of our cloud-slicing data indicates signatures of lightning-generated NO2 in the upper troposphere. Comparison of the climatology with simulations from the global modeling initiative (GMI) for cloudy conditions (cloud optical depth > 10) shows similarities in the spatial patterns of continental pollution outflow. However, there are also some differences in the seasonal variation of free-tropospheric NO2 VMRs near highly populated regions and in areas affected by lightning-generated NOx.

scholarly journals Rapid methods for inversion of MAXDOAS elevation profiles to surface-associated box concentrations, visibility, and heights: application to analysis of Arctic BrO events

2010 ◽  
Vol 3 (6) ◽  
pp. 4645-4674 ◽  
Author(s):  
D. Donohoue ◽  
D. Carlson ◽  
W. R. Simpson
Keyword(s):  
Column Density ◽  
Surface Concentration ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Data Set ◽  
Profile Method ◽  
Remote Sensing Technique ◽  
Vertical Column Density ◽  
Gas Layer

Abstract. Multiple Axis Differential Optical Absorption Spectroscopy (MAXDOAS) is a remote sensing technique that measures surface-associated trace gas profiles using simple automated instrumentation that requires very low power and is deployable at remote sites. However, the analysis of MAXDOAS data is complex and often cannot be applied rapidly or consistently over long measurement periods. Here we present three transparent methods to analyze MAXDOAS data. The box profile method finds the best trace gas layer height and surface-associated vertical column density (VCD) to simultaneously fit oxygen collisional dimer (O4) and trace gas differential slant column density (dSCD) observations. The elevated viewing method estimates the surface-associated VCD from observations at high view elevations, such as 10° and 20°. The horizon viewing method estimates the surface concentration of a trace gas by using near-horizon view trace gas and O4 data. We apply these methods to a two-month data set and show that the methods retrieve information 80% of the time and provides a consistent time series. Surface-associated trace gas VCD observations by the elevated viewing method correlate (r2 > 0.93) with the box profile method with slopes within 15% of unity. Surface-associated concentration observations from the horizon viewing method correlate well (r2 > 0.90) with the box profile method and a slope within 4% of unity. Application of these retrieval methods to UV-absorbing trace gases other than BrO is straightforward, and application in other spectral regions is discussed. These methods provide rapid and comprehensive inversions of MAXDOAS spectral data that are useful during field campaigns, as well as, verification of more complex (e.g. optimal estimate inversion) methods.

scholarly journals Near-surface and path-averaged mixing ratios of NO<sub>2</sub> derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study

2019 ◽  
Vol 19 (9) ◽  
pp. 5853-5879 ◽  
Author(s):  
Stefan F. Schreier ◽  
Andreas Richter ◽  
John P. Burrows
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Linear Regression Analysis ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Pollution Levels ◽  
Mixing Ratios ◽  
Tropospheric No2

Abstract. Nitrogen dioxide (NO2), produced as a result of fossil fuel combustion, biomass burning, lightning, and soil emissions, is a key urban and rural tropospheric pollutant. In this case study, ground-based remote sensing has been coupled with the in situ network in Vienna, Austria, to investigate NO2 distributions in the planetary boundary layer. Near-surface and path-averaged NO2 mixing ratios within the metropolitan area of Vienna are estimated from car DOAS (differential optical absorption spectroscopy) zenith-sky and tower DOAS horizon observations. The latter configuration is innovative in the sense that it obtains horizontal measurements at more than a hundred different azimuthal angles – within a 360∘ rotation taking less than half an hour. Spectral measurements were made with a DOAS instrument on nine days in April, September, October, and November 2015 in the zenith-sky mode and on five days in April and May 2016 in the off-axis mode. The analysis of tropospheric NO2 columns from the car measurements and O4 normalized NO2 path averages from the tower observations provide interesting insights into the spatial and temporal NO2 distribution over Vienna. Integrated column amounts of NO2 from both DOAS-type measurements are converted into mixing ratios by different methods. The estimation of near-surface NO2 mixing ratios from car DOAS tropospheric NO2 vertical columns is based on a linear regression analysis including mixing height and other meteorological parameters that affect the dilution and reactivity in the planetary boundary layer – a new approach for such conversion. Path-averaged NO2 mixing ratios are calculated from tower DOAS NO2 slant column densities by taking into account topography and geometry. Overall, lap averages of near-surface NO2 mixing ratios obtained from car DOAS zenith-sky measurements, around a circuit in Vienna, are in the range of 3.8 to 26.1 ppb and in good agreement with values obtained from in situ NO2 measurements for days with wind from the southeast. Path-averaged NO2 mixing ratios at 160 m above the ground as derived from the tower DOAS measurements are between 2.5 and 9 ppb on two selected days with different wind conditions and pollution levels and show similar spatial distribution as seen in the car DOAS zenith-sky observations. We conclude that the application of the two methods to obtain near-surface and path-averaged NO2 mixing ratios is promising for this case study.

scholarly journals Near-surface and path-averaged mixing ratios of NO<sub>2</sub> derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study

2018 ◽  
Author(s):  
Stefan F. Schreier ◽  
Andreas Richter ◽  
John P. Burrows
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Linear Regression Analysis ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Pollution Levels ◽  
Mixing Ratios ◽  
Tropospheric No2

Abstract. Nitrogen dioxide (NO2), produced as a result of fossil fuel combustion, biomass burning, lightning, and soil emissions, is a key urban and rural tropospheric pollutant. In this case study, ground-based remote sensing has been coupled with the in situ network in Vienna, Austria, to investigate NO2 distributions in the planetary boundary layer. Near-surface and path-averaged NO2 mixing ratios within the metropolitan area of Vienna are estimated from car DOAS (Differential Optical Absorption Spectroscopy) zenith-sky and tower DOAS horizon observations. The latter configuration is innovative in the sense that it obtains horizontal measurements at more than hundred different azimuthal angles – within a 360° rotation taking less than half an hour. Spectral measurements were made with a DOAS instrument on nine days in April, September, October, and November 2015 in the zenith-sky mode and on five days in April and May 2016 in the off-axis mode. The analysis of tropospheric NO2 columns from the car measurements and O4 normalized NO2 path averages from the tower observations provide interesting insights into the spatial and temporal NO2 distribution over Vienna. Integrated column amounts of NO2 from both DOAS-type measurements are converted into mixing ratios by different methods. The estimation of near-surface NO2 mixing ratios from car DOAS tropospheric NO2 vertical columns is based on a linear regression analysis including mixing-height and other meteorological parameters that affect the dilution and reactivity in the planetary boundary layer – a new approach for such conversion. Path-averaged NO2 mixing ratios are calculated from tower DOAS NO2 slant column densities by taking into account topography and geometry. Overall, lap averages of near-surface NO2 mixing ratios obtained from car DOAS zenith-sky measurements, around a circuit in Vienna, are in the range of 3.8 to 26.2 ppb and in good agreement with values obtained from in situ NO2 measurements for days with wind from the Southeast. Path-averaged NO2 mixing ratios at 160 m above the ground as derived from the tower DOAS measurements are between 2.5 and 9 ppb on two selected days with different wind conditions and pollution levels and show similar spatial distribution as seen in the car DOAS zenith-sky observations. We conclude that the application of the two methods to obtain near-surface and path-averaged NO2 mixing ratios is promising for this case study.

scholarly journals Ability of the MAX-DOAS method to derive profile information for NO<sub>2</sub>: can the boundary layer and free troposphere be separated?

2011 ◽  
Vol 4 (12) ◽  
pp. 2659-2684 ◽  
Author(s):  
T. Vlemmix ◽  
A. J. M. Piters ◽  
A. J. C. Berkhout ◽  
L. F. L. Gast ◽  
P. Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
A Priori ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Free Troposphere ◽  
Average Difference ◽  
Retrieval Models ◽  
Error Sources ◽  
Profile Information ◽  
Tropospheric No2

Abstract. Multiple Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instruments can measure from the ground the absorption by nitrogen dioxide (NO2) of scattered sunlight seen in multiple viewing directions. This paper studies the potential of this technique to derive the vertical distribution of NO2 in the troposphere. Such profile information is essential for detailed comparisons of MAX-DOAS retrievals with other measurement techniques for NO2, e.g. with a lidar or from space. The retrieval algorithm used is based on a pre-calculated look-up table and assumes homogeneous mixing of aerosols and NO2 in layers extending from the surface to a variable height. Two retrieval models are compared: one including and one excluding an elevated NO2 layer at a fixed altitude in the free troposphere. An ensemble technique is applied to derive retrieval uncertainties. Sensitivity studies demonstrate that NO2 in the free troposphere can only be retrieved accurately if: (i) the retrieved boundary layer profiles for aerosols and NO2 correspond to the real ones, (ii) if the right a-priori choice is made for the (average) height of free tropospheric NO2, and (iii) if all other error sources are very low. It is shown that retrieval models that are capable of accurate NO2 retrievals in the free troposphere, i.e. models not constrained too much by a-priori assumptions, have as a major disadvantage that they will frequently find free tropospheric NO2, also when it is not present in reality. This is a consequence of the fact that NO2 in the free troposphere is poorly constrained by the MAX-DOAS observations, especially for high aerosol optical thickness values in the boundary layer. Retrieval of free tropospheric NO2 is therefore sensitive to a large number of error sources. For this reason it is advised to firmly constrain free tropospheric NO2 in MAX-DOAS retrieval models used for applications such as satellite validation. This effectively makes free tropospheric NO2 a source of error for MAX-DOAS retrieval of NO2 profiles in the boundary layer. A comparison was performed with independent data, based on MAX-DOAS observations done at the CINDI campaign, held in the Netherlands in 2009. Comparison with lidar partial tropospheric NO2 columns showed a correlation of 0.78, and an average difference of 0.1× 1015 molec cm−2. The diurnal evolution of the NO2 volume mixing ratio measured by in-situ monitors at the surface and averaged over five days with cloud-free mornings, compares well to the MAX-DOAS retrieval: a correlation was found of 0.94, and an average difference of 0.04 ppb.

Evaluation of TROPOMI cloud products for NO2 retrievals

2020 ◽  
Author(s):  
Miriam Latsch ◽  
Andreas Richter ◽  
John P. Burrows ◽  
Thomas Wagner ◽  
Holger Silher ◽  
...  
Keyword(s):  
Recognition Algorithm ◽  
Trace Gas ◽  
Oxygen Absorption ◽  
Absorption Bands ◽  
Data Set ◽  
Gas Processing ◽  
Trace Species ◽  
Retrieval Scheme ◽  
First Results ◽  
Reflecting Boundaries

&lt;p&gt;The first European Sentinel satellite for monitoring the composition of the Earth&amp;#8217;s atmosphere, the Sentinel 5 Precursor (S5p), carries the TROPOspheric Monitoring Instrument (TROPOMI) on board to map trace species of the global atmosphere at high spatial resolution. Retrievals of tropospheric trace gas columns from satellite measurements are strongly influenced by clouds. Thus, cloud retrieval algorithms were developed and implemented in the trace gas processing chain to consider this impact.&lt;/p&gt;&lt;p&gt;In this study, different cloud products available for NO&lt;sub&gt;2&lt;/sub&gt; retrievals from TROPOMI data are analyzed. The TROPOMI level 2 OCRA/ROCINN (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks) cloud products CRB (cloud as reflecting boundaries) and CAL (clouds as layers) as well as the FRESCO (Fast Retrieval Scheme for Clouds from Oxygen absorption bands) cloud product are compared with regard to e. g. cloud fraction, cloud height, cloud albedo/optical thickness, flagging and quality indicators. In particular, difficult situations such as snow or ice, sun glint, and high aerosol load are investigated.&lt;/p&gt;&lt;p&gt;The eventual aim of this study is to better understand TROPOMI cloud products and their quantitative impacts on trace gas retrievals. Here, we present first results of a statistical analysis on a limited data set comparing currently existing cloud products and their approaches focusing on NO&lt;sub&gt;2&lt;/sub&gt;.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document