Parameterization retrieval of trace gas volume mixing ratios from airborne MAX-DOAS

Abstract. We present a parameterization retrieval of volume mixing ratios (VMR) from differential slant column density (dSCD) measurements by airborne multi-axis differential optical absorption spectroscopy (AMAX-DOAS). The method makes use of the fact that horizontally recorded limb spectra (elevation angle 0°) are strongly sensitive to the atmospheric layer at instrument altitude. These limb spectra are analysed using reference spectra that largely cancel out column contributions from above and below the instrument, so that the resulting limb dSCDs, i.e., the column integrated concentration with respect to a reference spectrum, are almost exclusively sensitive to the atmospheric layers around instrument altitude. The conversion of limb dSCDs into VMRs is then realized by calculating box-air mass factors (Box-AMFs) for a Rayleigh atmosphere and applying a scaling factor constrained by O4 dSCDs to account for aerosol extinction. An iterative VMR retrieval scheme corrects for trace gas profile shape effects. Benefits of this method are 1) a fast conversion that only requires the computation of Box-AMFs in a Rayleigh atmosphere; 2) neither local aerosol extinction nor the slant column density in the DOAS reference (SCDref) need to be known; and 3) VMRs can be retrieved for every measurement point along a flight track, in contrast to profile inversion techniques. Sensitivity studies are performed for bromine monoxide (BrO), iodine monoxide (IO) and nitrogen dioxide (NO2), using 1) simulated dSCD data for different trace gas and aerosol profiles; and 2) field measurements from the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) field experiment. For simulated data in a Rayleigh atmosphere, the agreement between the VMR from the parameterization method (VMRpara) and the true VMR (VMRtrue) is excellent for all trace gases. Offsets, slopes and R2 values for the linear fit of VMRpara over VMRtrue are as follows: BrO: (0.008 ± 0.001) pptv, 0.988 ± 0.001, 0.987; IO: (−0.0066 ± 0.0001) pptv, 1.0021 ± 0.0003, 0.9979; NO2: (−0.17 ± 0.03) pptv, 1.0036 ± 0.0001, 0.9997. The agreement for atmospheres with aerosol shows comparable R2 values to the Rayleigh case, but slopes deviate a bit more from one: BrO: (0.093 ± 0.002) pptv, 0.933 ± 0.002, 0.907; IO: (0.0021 ± 0.0004) pptv, 0.887 ± 0.001, 0.973; NO2: (8.5 ± 0.1) pptv, 0.8302 ± 0.0006, 0.9923. VMRpara from field data are further compared with optimal estimation retrievals (VMROE). Least orthogonal distance fit of the data give the following equations: BrOpara = (0.1 ± 0.2) pptv + (0.95 ± 0.14) x BrOOE; IOpara = (0.01 ± 0.02) pptv + (1.00 ± 0.12) x IOOE; NO2para = (1.7 ± 8.0) pptv + (0.90 ± 0.51) x NO2OE. Overall, we conclude that the parameterization retrieval is accurate with an uncertainty of 20 % for IO, 30 % for BrO and NO2, but not better than 0.05 pptv IO, 0.5 pptv BrO, and 10 pptv NO2. The retrieval is applicable over a wide range of atmospheric conditions and measurement geometries, and not limited to the interpretation of vertical profile measurements in the remote troposphere.

Download Full-text

Parameterization retrieval of trace gas volume mixing ratios from Airborne MAX-DOAS

Atmospheric Measurement Techniques ◽

10.5194/amt-9-5655-2016 ◽

2016 ◽

Vol 9 (11) ◽

pp. 5655-5675 ◽

Cited By ~ 11

Author(s):

Barbara Dix ◽

Theodore K. Koenig ◽

Rainer Volkamer

Keyword(s):

Column Density ◽

Elevation Angle ◽

Trace Gas ◽

Optical Absorption Spectroscopy ◽

Aerosol Extinction ◽

Reference Spectrum ◽

Atmospheric Conditions ◽

Tropical Ocean ◽

Mixing Ratios ◽

Wide Range

Abstract. We present a parameterization retrieval of volume mixing ratios (VMRs) from differential slant column density (dSCD) measurements by Airborne Multi-AXis Differential Optical Absorption Spectroscopy (AMAX-DOAS). The method makes use of the fact that horizontally recorded limb spectra (elevation angle 0°) are strongly sensitive to the atmospheric layer at instrument altitude. These limb spectra are analyzed using reference spectra that largely cancel out column contributions from above and below the instrument, so that the resulting limb dSCDs, i.e., the column integrated concentration with respect to a reference spectrum, are almost exclusively sensitive to the atmospheric layers around instrument altitude. The conversion of limb dSCDs into VMRs is then realized by calculating box air mass factors (Box-AMFs) for a Rayleigh atmosphere and applying a scaling factor constrained by O4 dSCDs to account for aerosol extinction. An iterative VMR retrieval scheme corrects for trace gas profile shape effects. Benefits of this method are (1) a fast conversion that only requires the computation of Box-AMFs in a Rayleigh atmosphere; (2) neither local aerosol extinction nor the slant column density in the DOAS reference (SCDref) needs to be known; and (3) VMRs can be retrieved for every measurement point along a flight track, thus increasing statistics and adding flexibility to capture concentration gradients. Sensitivity studies are performed for bromine monoxide (BrO), iodine monoxide (IO) and nitrogen dioxide (NO2), using (1) simulated dSCD data for different trace gas and aerosol profiles and (2) field measurements from the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) field experiment. For simulated data in a Rayleigh atmosphere, the agreement between the VMR from the parameterization method (VMRpara) and the true VMR (VMRtrue) is excellent for all trace gases. Offsets, slopes and R2 values for the linear fit of VMRpara over VMRtrue are, respectively (0.008 ± 0.001) pptv, 0.988 ± 0.001, 0.987 for BrO; (−0.0066 ± 0.0001) pptv, 1.0021 ± 0.0003, 0.9979 for IO; (−0.17 ± 0.03) pptv, 1.0036 ± 0.0001, 0.9997 for NO2. The agreement for atmospheres with aerosol shows comparable R2 values to the Rayleigh case, but slopes deviate a bit more from one: (0.093 ± 0.002) pptv, 0.933 ± 0.002, 0.907 for BrO; (0.0021 ± 0.0004) pptv, 0.887 ± 0.001, 0.973 for IO; (8.5 ± 0.1) pptv, 0.8302 ± 0.0006, 0.9923 for NO2. VMRpara from field data are further compared with optimal estimation retrievals (VMROE). Least orthogonal distance fit of the data give the following equations: BrOpara =  (0.1 ± 0.2) pptv + (0.95 ± 0.14)  ×  BrOOE; IOpara =  (0.01 ± 0.02) pptv + (1.00 ± 0.12)  ×  IOOE; NO2para  =  (3.9 ± 2.5) pptv + (0.87 ± 0.15)  ×  NO2OE. Overall, we conclude that the parameterization retrieval is accurate with an uncertainty of 20 % for IO, 30 % for BrO and NO2, but not better than 0.05 pptv IO, 0.5 pptv BrO and 10 pptv NO2. The retrieval is applicable over a wide range of atmospheric conditions and measurement geometries and not limited to the interpretation of vertical profile measurements in the remote troposphere.

Download Full-text

The horizontal resolution of MIPAS

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-1-103-2008 ◽

2008 ◽

Vol 1 (1) ◽

pp. 103-125 ◽

Cited By ~ 5

Author(s):

T. von Clarmann ◽

C. De Clercq ◽

M. Ridolfi ◽

M. Höpfner ◽

J.-C. Lambert

Keyword(s):

Michelson Interferometer ◽

Elevation Angle ◽

Emission Spectra ◽

Horizontal Resolution ◽

Atmospheric Composition ◽

Trace Gas ◽

Atmospheric Conditions ◽

Tangent Point ◽

High Vertical Resolution ◽

Along Track

Abstract. Limb remote sensing from space provides atmospheric composition measurements at high vertical resolution while the information is smeared in the horizontal domain. The horizontal components of two-dimensional (altitude and along-track coordinate) averaging kernels of a limb retrieval constrained to horizontal homogeneity can be used to estimate the horizontal resolution of limb retrievals. This is useful for comparisons of measured data with modeled data, to construct horizontal observation operators in data assimilation applications or when measurements of different horizontal resolution are intercompared. We present these averaging kernels for retrievals of temperature, H2O, O3, CH4, N2O, HNO3 and NO2 from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) high-resolution limb emission spectra. The horizontal smearing of a MIPAS retrieval in terms of full width at half maximum of the rows of the horizontal averaging kernel matrix varies typically between about 200 and 350 km for most species, altitudes and atmospheric conditions. The range where 95% of the information originates from varies from about 260 to 440 km for these cases. This information spread is smaller than the MIPAS horizontal sampling, i.e. MIPAS data are horizontally undersampled, and the effective horizontal resolution is driven by the sampling rather than the smearing. The point where the majority of the information originates from is displaced from the tangent point towards the satellite by typically less than 10 km for trace gas profiles and about 50 to 100 km for temperature, with a few exceptions for uppermost altitudes. The geolocation of a MIPAS profile is defined as the tangent point of the middle line of sight in a MIPAS limb scan. The majority of the information displacement with respect to this nominal geolocation of the measurement is caused by the satellite movement and the geometrical displacement of the actual tangent point as a function of the elevation angle. In none of the cases investigated, propagation of the horizontal smoothing on the vertical profile shape has been observed.

Download Full-text

Aircraft measurements of bromine monoxide, iodine monoxide, and glyoxal profiles in the tropics: comparison with ship-based and in situ measurements

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-623-2015 ◽

2015 ◽

Vol 8 (1) ◽

pp. 623-687 ◽

Cited By ~ 2

Author(s):

R. Volkamer ◽

S. Baidar ◽

T. L. Campos ◽

S. Coburn ◽

J. P. DiGangi ◽

...

Keyword(s):

Tropospheric Chemistry ◽

Optical Absorption Spectroscopy ◽

Reference Spectrum ◽

Validation Data ◽

Tropical Ocean ◽

Near Surface ◽

Oxygenated Hydrocarbons ◽

Iodine Monoxide

Abstract. Tropospheric chemistry of halogens and organic carbon over tropical oceans modifies ozone and atmospheric aerosols, yet atmospheric models remain largely untested for lack of vertically resolved measurements of bromine monoxide (BrO), iodine monoxide (IO), and small oxygenated hydrocarbons like glyoxal (CHOCHO) in the tropical troposphere. BrO, IO, glyoxal, nitrogen dioxide (NO2), water vapor (H2O) and O2-O2 collision complexes (O4) were measured by the CU Airborne Multi AXis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument, in situ aerosol size distributions by an Ultra High Sensitivity Aerosol Spectrometer (UHSAS), and in situ H2O by Vertical-Cavity Surface-Emitting Laser hygrometer (VCSEL). Data are presented from two research flights (RF12, RF17) aboard the NSF/NCAR GV aircraft over the tropical Eastern Pacific Ocean (tEPO) as part of the "Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated hydrocarbons" (TORERO) project. We assess the accuracy of O4 slant column density (SCD) measurements in the presence and absence of aerosols, and find O4-inferred aerosol extinction profiles at 477 nm agree within 5% with Mie calculations of extinction profiles constrained by UHSAS. CU AMAX-DOAS provides a flexible choice of geometry which we exploit to minimize the SCD in the reference spectrum (SCDREF, maximize signal-to-noise), and to test the robustness of BrO, IO, and glyoxal differential SCDs. The RF12 case study was conducted in pristine marine and free tropospheric air. The RF17 case study was conducted above the NOAA RV Ka'imimoana (TORERO cruise, KA-12-01), and provides independent validation data from ship-based in situ Cavity Enhanced- and MAX-DOAS. Inside the marine boundary layer (MBL) no BrO was detected (smaller than 0.5 pptv), and 0.2–0.55 pptv IO and 32–36 pptv glyoxal were observed. The near surface concentrations agree within 20% (IO) and 10% (glyoxal) between ship and aircraft. The BrO concentration strongly increased with altitude to 3.0 pptv at 14.5 km (RF12, 9.1 to 8.6° N; 101.2 to 97.4° W). At 14.5 km 5–10 pptv NO2 agree with model predictions, and demonstrate good control over separating tropospheric from stratospheric absorbers (NO2 and BrO). Our profile retrievals have 12–20 degrees of freedom (DoF), and up to 500 m vertical resolution. The tropospheric BrO VCD was 1.5 × 1013 molec cm−2 (RF12), and at least 0.5 × 1013 molec cm−2 (RF17, 0–10 km, lower limit). Tropospheric IO VCDs correspond to 2.1 × 1012 molec cm−2 (RF12) and 2.5 × 1012 molec cm−2 (RF17), and glyoxal VCDs of 2.6 × 1014 molec cm−2 (RF12) and 2.7 × 1014 molec cm−2 (RF17). Surprisingly, essentially all BrO, and the dominant IO and glyoxal VCD fraction was located above 2 km (IO: 58 ± 5%, 0.1–0.2 pptv; glyoxal: 52 ± 5%, 3–20 pptv). To our knowledge there are no previous vertically resolved measurements of BrO and glyoxal from aircraft in the tropical free troposphere.

Download Full-text

MAX-DOAS measurements of NO2, SO2, HCHO, and BrO at the Mt. Waliguan WMO GAW global baseline station in the Tibetan Plateau

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-6973-2020 ◽

2020 ◽

Vol 20 (11) ◽

pp. 6973-6990 ◽

Cited By ~ 1

Author(s):

Jianzhong Ma ◽

Steffen Dörner ◽

Sebastian Donner ◽

Junli Jin ◽

Siyang Cheng ◽

...

Keyword(s):

Tibetan Plateau ◽

Trace Gases ◽

Elevation Angle ◽

Lower Troposphere ◽

Statistical Error ◽

Tropospheric Chemistry ◽

Ozone Production ◽

Optical Absorption Spectroscopy ◽

The Tibetan Plateau ◽

Mixing Ratios

Abstract. Mt. Waliguan Observatory (WLG) is a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) global baseline station in China. WLG is located at the northeastern part of the Tibetan Plateau (36∘17′ N, 100∘54′ E, 3816 m a.s.l.) and is representative of the pristine atmosphere over the Eurasian continent. We made long-term ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements at WLG during the period 2012–2015. In this study, we retrieve the differential slant column densities (dSCDs) and estimate the tropospheric background mixing ratios of different trace gases, including NO2, SO2, HCHO, and BrO, using the measured spectra at WLG. Averaging of 10 original spectra is found to be an “optimum option” for reducing both the statistical error of the spectral retrieval and systematic errors in the analysis. The dSCDs of NO2, SO2, HCHO, and BrO under clear-sky and low-aerosol-load conditions are extracted from measured spectra at different elevation angles at WLG. By performing radiative transfer simulations with the model TRACY-2, we establish approximate relationships between the trace gas dSCDs at 1∘ elevation angle and the corresponding average tropospheric background volume mixing ratios. Mixing ratios of these trace gases in the lower troposphere over WLG are estimated to be in a range of about 7 ppt (January) to 100 ppt (May) for NO2, below 0.5 ppb for SO2, between 0.4 and 0.9 ppb for HCHO, and lower than 0.3 ppt for BrO. The chemical box model simulations constrained by the NO2 concentration from our MAX-DOAS measurements show that there is a little net ozone loss (−0.8 ppb d−1) for the free-tropospheric conditions and a little net ozone production (0.3 ppb d−1) for the boundary layer conditions over WLG during summertime. Our study provides valuable information and data sets for further investigating tropospheric chemistry in the background atmosphere and its links to anthropogenic activities.

Download Full-text

Tropospheric NO2 and HCHO derived from dual-scan MAX-DOAS measurements in Uccle (Belgium) and application to S5P/TROPOMI validation

10.5194/egusphere-egu2020-17181 ◽

2020 ◽

Author(s):

Ermioni Dimitropoulou ◽

Francois Hendrick ◽

Martine M. Friedrich ◽

Gaia Pinardi ◽

Frederik Tack ◽

...

Keyword(s):

Vertical Profile ◽

A Priori ◽

Elevation Angle ◽

Optical Absorption Spectroscopy ◽

Azimuthal Direction ◽

Inversion Algorithm ◽

Vertical Column ◽

Near Surface ◽

Mixing Ratios ◽

Horizontal Variation

Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of aerosols, tropospheric nitrogen dioxide (NO2) and formaldehyde (HCHO) have been carried out in Uccle, Brussels, during two years (March 2018 &#8211; March 2020). The MAX-DOAS instrument has been operating in both UV and visible (Vis) wavelength ranges in a dual-scan configuration consisting of two sub-modes: (1) an elevation scan in a fixed viewing azimuthal direction (the so-called main azimuthal direction) pointing and (2) an azimuthal scan in a fixed low elevation angle (2o). By applying a vertical profile inversion algorithm in the main azimuthal direction and an adapted version of the parameterization technique proposed by Sinreich et al. (2013) in the other azimuthal directions, near-surface &#160;concentrations (VMRs) and vertical column densities (VCDs) are retrieved in ten different azimuthal directions.The present work focuses on the seasonal horizontal variation of NO2 and HCHO around the measurement site. The observations show a clear seasonal cycle of these trace gases. An important application of the dual-scan MAX-DOAS measurements is the validation of satellite missions with high spatial resolution, such as TROPOMI/S5P. Measuring the tropospheric &#160;VCDs in different azimuthal directions is shown to improve the spatial colocation with satellite measurements leading to a better agreement between both datasets. By using &#160;vertical profile information derived from the MAX-DOAS measurements, we show that a persistent systematic underestimation of the TROPOMI &#160;data can be explained by uncertainties in the a-priori NO2 profile shape in the satellite retrieval. A similar validation study for TROPOMI HCHO is currently under progress and preliminary results will be presented.References:Sinreich, R., Merten, A., Molina, L., and Volkamer, R.: Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box-averaged mixing ratios, Atmos. Meas. Tech., 6, 1521&#8211;1532, https://doi.org/10.5194/amt-6-1521-2013, 2013.

Download Full-text

The Airyx 2D SkySpec instrument: MAX-DOAS measurements of tropospheric NO2 and HCHO in Munich and the comparison to satellite observations

10.5194/egusphere-egu2020-8941 ◽

2020 ◽

Author(s):

Johannes Lampel ◽

Ka Lok Chan ◽

Denis Pöhler ◽

Matthias Wiegner ◽

Carlos Alberti ◽

...

Keyword(s):

Pearson Correlation ◽

Satellite Observations ◽

Optical Absorption Spectroscopy ◽

Aerosol Extinction ◽

Aerosol Formation ◽

Mixing Ratios ◽

Monitor Data ◽

Sun Light ◽

Good Agreement

We present the Airyx 2D SkySpec Instrument: A commercially available two-dimensionally scanning Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) setup for the observations of trace gases using spectral measurements of scattered sun light and optionally also direct sun light. The waterproof design of the scanner unit is designed for long-term outdoor deployment. Temperature stabilisation of the spectrometers and automatic calibration spectra measurement are used to ensure high-quality measurement data over months and years of observations.We show 2.5 years of measurements in Munich. Vertical columns and vertical distribution profiles of aerosol extinction coefficient, NO2 and HCHO are retrieved from the 2D MAX-DOAS observations. The measured surface aerosol extinction coefficients and NO2 mixing ratios are compared to in-situ monitor data. The retrieved surface NO2 mixing ratios show good agreement with in-situ monitor data with a Pearson correlation coefficient (R) of 0.91. Good agreement (R= 0.80) is also found for AOD when compared to sun-photometer measurements. Tropospheric vertical column densities (VCDs) of NO2 and HCHO derived from the MAX-DOAS measurements are also used to validate OMI and TROPOMI satellite observations. Monthly averaged data show good correlation, however, satellite observations are on average 30% lower than the MAX-DOAS measurements. Furthermore, the 2D MAX-DOAS observations are used to investigate the spatio-temporal characteristic of NO2 and HCHO in Munich. Analysis of the relations among aerosol, NO2 and HCHO show higher aerosol to HCHO ratios in winter indicating a longer atmospheric lifetime of aerosol and HCHO. The analysis also suggests that secondary aerosol formation is the major source of aerosols in Munich.

Download Full-text

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

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-7641-2012 ◽

2012 ◽

Vol 5 (5) ◽

pp. 7641-7673 ◽

Cited By ~ 1

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.

Download Full-text

Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies on field data from the CINDI-2 campaign

10.5194/amt-2019-456 ◽

2020 ◽

Cited By ~ 8

Author(s):

Jan-Lukas Tirpitz ◽

Udo Frieß ◽

François Hendrick ◽

Carlos Alberti ◽

Marc Allaart ◽

...

Keyword(s):

Lower Troposphere ◽

Trace Gas ◽

Optical Absorption Spectroscopy ◽

Measuring Instruments ◽

Visible Radiation ◽

Radiation Spectra ◽

Tropospheric Aerosol ◽

Wide Range ◽

Sun Photometer ◽

Low Sensitivity

Abstract. Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a well-established ground-based measurement technique for the detection of aerosols and trace gases particularly in the boundary layer and the lower troposphere: ultraviolet- and visible radiation spectra of skylight are analysed to obtain information on different atmospheric parameters, integrated over the light path from space to the instrument. An appropriate set of spectra recorded under different viewing geometries ("Multi-Axis") allows retrieval of tropospheric aerosol and trace gas vertical distributions by applying numerical inversion methods. The second Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI-2) took place in Cabauw (The Netherlands) in September 2016 with the aim of assessing the consistency of MAX-DOAS measurements of tropospheric species (NO2, HCHO, O3, HONO, CHOCHO and O4). This was achieved through the coordinated operation of 36 spectrometers operated by 24 groups from all over the world, together with a wide range of supporting reference observations (in situ analysers, balloon sondes, lidars, Long-Path DOAS, sun photometer and others). In the presented study, the retrieved CINDI-2 MAX-DOAS trace gas (NO2, HCHO) and aerosol vertical profiles of 15 participating groups using different inversion algorithms are compared and validated against the colocated supporting observations. The profiles were found to be in good qualitative agreement: most participants obtained the same features in the retrieved vertical trace gas and aerosol distributions, however sometimes at different altitudes and of different intensity. Under clear sky conditions, the root-mean-square differences of aerosol optical thicknesses, trace gas (NO2, HCHO) vertical columns and surface concentrations among the results of individual participants vary between 0.01–0.1, (1.5–15) x 1014 molec cm-2 and (0.3–8) x 1010 molec cm-3, respectively. For the comparison against supporting observations, these values increase to 0.02–0.2, (11–55) x 1014 molec cm-2 and (0.8–9) x 1010 molec cm-3. It is likely that a large part of this increase is caused by imperfect spatio-temporal overlap of the different observations. In contrast to what is often assumed, the MAX-DOAS vertically integrated extinction profiles and the sun photometer total aerosol optical thickness were found to not necessarily being comparable quantities, unless information on the real aerosol vertical distribution is available to account for the low sensitivity of MAX-DOAS observations at higher altitudes.

Download Full-text

The horizontal resolution of MIPAS

Atmospheric Measurement Techniques ◽

10.5194/amt-2-47-2009 ◽

2009 ◽

Vol 2 (1) ◽

pp. 47-54 ◽

Cited By ~ 48

Author(s):

T. von Clarmann ◽

C. De Clercq ◽

M. Ridolfi ◽

M. Höpfner ◽

J.-C. Lambert

Keyword(s):

Michelson Interferometer ◽

Elevation Angle ◽

Emission Spectra ◽

Horizontal Resolution ◽

Atmospheric Composition ◽

Trace Gas ◽

Atmospheric Conditions ◽

Tangent Point ◽

High Vertical Resolution ◽

Along Track

Download Full-text

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

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-3-4645-2010 ◽

2010 ◽

Vol 3 (6) ◽

pp. 4645-4674 ◽

Cited By ~ 3

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.

Download Full-text

Parameterization retrieval of trace gas volume mixing ratios from airborne MAX-DOAS