scholarly journals MAX-DOAS formaldehyde slant column measurements during CINDI: intercomparison and analysis improvement

2013 ◽  
Vol 6 (1) ◽  
pp. 167-185 ◽  
Author(s):  
G. Pinardi ◽  
M. Van Roozendael ◽  
N. Abuhassan ◽  
C. Adams ◽  
A. Cede ◽  
...  
Keyword(s):  
Cross Sections ◽  
Cross Correlation ◽  
Optical Absorption Spectroscopy ◽  
Integration Time ◽  
Measuring Instruments ◽  
Absorption Cross ◽  
Correlation Effects ◽  
Data Set ◽  
Random Uncertainties ◽  
Ring Effect

Abstract. We present intercomparison results for formaldehyde (HCHO) slant column measurements performed during the Cabauw Intercomparison campaign of Nitrogen Dioxide measuring Instruments (CINDI) that took place in Cabauw, the Netherlands, in summer 2009. During two months, nine atmospheric research groups simultaneously operated MAX-DOAS (MultiAXis Differential Optical Absorption Spectroscopy) instruments of various designs to record UV-visible spectra of scattered sunlight at different elevation angles that were analysed using common retrieval settings. The resulting HCHO data set was found to be highly consistent, the mean difference between instruments generally not exceeding 15% or 7.5 × 1015 molec cm−2, for all viewing elevation angles. Furthermore, a sensitivity analysis was performed to investigate the uncertainties in the HCHO slant column retrieval when varying key input parameters such as the molecular absorption cross sections, correction terms for the Ring effect or the width and position of the fitting interval. This study led to the identification of potentially important sources of errors associated with cross-correlation effects involving the Ring effect, O4, HCHO and BrO cross sections and the DOAS closure polynomial. As a result, a set of updated recommendations was formulated for HCHO slant column retrieval in the 336.5–359 nm wavelength range. To conclude, an error budget is proposed which distinguishes between systematic and random uncertainties. The total systematic error is estimated to be of the order of 20% and is dominated by uncertainties in absorption cross sections and related spectral cross-correlation effects. For a typical integration time of one minute, random uncertainties range between 5 and 30%, depending on the noise level of individual instruments.

scholarly journals MAXDOAS formaldehyde slant column measurements during CINDI: intercomparison and analysis improvement

2012 ◽  
Vol 5 (5) ◽  
pp. 6679-6732 ◽  
Author(s):  
G. Pinardi ◽  
M. Van Roozendael ◽  
N. Abuhassan ◽  
C. Adams ◽  
A. Cede ◽  
...  
Keyword(s):  
Cross Sections ◽  
Cross Correlation ◽  
Integration Time ◽  
Measuring Instruments ◽  
Absorption Cross ◽  
Correlation Effects ◽  
Visible Spectra ◽  
Correction Terms ◽  
Random Uncertainties ◽  
Ring Effect

Abstract. We present intercomparison results for formaldehyde (HCHO) slant column measurements performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) that took place in Cabauw, the Netherlands, in summer 2009. During two months, nine atmospheric research groups simultaneously operated MAXDOAS instruments of various designs to record UV-visible spectra of scattered sunlight at different elevation angles that were analysed using common retrieval settings. The resulting HCHO dataset was found to be highly consistent, the mean difference between instruments generally not exceeding 15% or 7.5 × 1015 molec cm2, for all viewing elevation angles. Furthermore, a sensitivity analysis was performed to investigate the uncertainties in the HCHO slant column retrieval when varying key input parameters such as the molecular absorption cross-sections, correction terms for the Ring effect or the width and position of the fitting interval. This study led to the identification of potentially important sources of errors associated with cross-correlation effects involving the Ring effect, O4, HCHO and BrO cross-sections and the DOAS closure polynomial. As a result, a set of updated recommendations was formulated for HCHO slant column retrieval in the 336.5–359 nm wavelength range. To conclude, an error budget is proposed which distinguishes between systematic and random uncertainties. The total systematic error is estimated to be of the order of 20% and is dominated by uncertainties in absorption cross-sections and related spectral cross-correlation effects. For a typical integration time of one minute, random uncertainties range between 5% and 30%, depending on the noise level of individual instruments.

scholarly journals An improved glyoxal retrieval from OMI measurements

2014 ◽  
Vol 7 (12) ◽  
pp. 4133-4150 ◽  
Author(s):  
L. M. A. Alvarado ◽  
A. Richter ◽  
M. Vrekoussis ◽  
F. Wittrock ◽  
A. Hilboll ◽  
...  
Keyword(s):  
Cross Sections ◽  
Anthropogenic Activities ◽  
Absorption Cross ◽  
Fire Event ◽  
Data Set ◽  
Polynomial Degree ◽  
Temperature Boundary ◽  
Sensitivity Tests ◽  
Radiative Power ◽  
The Impact

Abstract. Satellite observations from the SCIAMACHY, GOME-2 and OMI spectrometers have been used to retrieve atmospheric columns of glyoxal (CHOCHO) with the DOAS method. High CHOCHO levels were found over regions with large biogenic and pyrogenic emissions, and hot-spots have been identified over areas of anthropogenic activities. This study focuses on the development of an improved retrieval for CHOCHO from measurements by the OMI instrument. From sensitivity tests, a fitting window and a polynomial degree are determined. Two different approaches to reduce the interference of liquid water absorption over oceanic regions are evaluated, achieving significant reduction of the number of negative columns over clear water regions. The impact of using different absorption cross-sections for water vapour is evaluated and only small differences are found. Finally, a high-temperature (boundary layer ambient: 294 K) absorption cross-section of nitrogen dioxide (NO2) is introduced in the DOAS retrieval to account for potential interferences of NO2 over regions with large anthropogenic emissions, leading to improved fit quality over these areas. A comparison with vertical CHOCHO columns retrieved from GOME-2 and SCIAMACHY measurements over continental regions is performed, showing overall good consistency. However, SCIAMACHY CHOCHO columns are systematically higher than those obtained from the other instruments. Using the new OMI CHOCHO data set, the link between fires and glyoxal columns is investigated for two selected regions in Africa. In addition, mapped averages are computed for a fire event in Russia between mid-July and mid-August 2010. In both cases, enhanced CHOCHO levels are found in close spatial and temporal proximity to elevated levels of MODIS fire radiative power, demonstrating that pyrogenic emissions can be clearly identified in the new OMI CHOCHO product.

scholarly journals Scattering and Absorption Cross-sections of Atmospheric Gases in the Ultraviolet-Visible Wavelength Range (307–725 nm)

2020 ◽  
Author(s):  
Quanfu He ◽  
Zheng Fang ◽  
Ofir Shoshamin ◽  
Steven S. Brown ◽  
Yinon Rudich
Keyword(s):  
Refractive Index ◽  
Wavelength Range ◽  
Cross Sections ◽  
Rayleigh Scattering ◽  
Dispersion Relations ◽  
Optical Absorption Spectroscopy ◽  
Absorption Cross ◽  
Atmospheric Gases ◽  
Scattering Cross ◽  
Scattering Cross Sections

Abstract. Accurate Rayleigh scattering and absorption cross-sections of atmospheric gases are essential for understanding the propagation of electromagnetic radiation in planetary atmospheres. Accurate extinction cross-sections are also essential for calibrating high finesse optical cavities and differential optical absorption spectroscopy and for accurate remote sensing. In this study, we measured the scattering and absorption cross-sections of carbon dioxide, nitrous oxide, sulfur hexafluoride, oxygen, and methane in the continuous wavelength range of 307–725 nm using Broadband Cavity Enhanced Spectroscopy (BBCES). The experimentally derived Rayleigh scattering cross-sections for CO2, N2O, SF6, O2, and CH4 agree with refractive index-based calculations, with a difference of 1.5 % and 1.1 %, 1.5 %, 2.9 %, and 1.4 % on average, respectively. The O2-O2 collision-induced absorption and absorption by methane are obtained with high precision at the 0.8 nm resolution of our BBCES instrument in the 307–725 nm wavelength range. New dispersion relations for N2O, SF6, and CH4 were derived using data in the UV-vis wavelength range. This study provides improved refractive index dispersion relations, n-based Rayleigh scattering cross-sections, and absorption cross-sections for these gases.

scholarly journals Tropospheric nitrogen dioxide column retrieval from ground-based zenith–sky DOAS observations

2015 ◽  
Vol 8 (6) ◽  
pp. 2417-2435 ◽  
Author(s):  
F. Tack ◽  
F. Hendrick ◽  
F. Goutail ◽  
C. Fayt ◽  
A. Merlaud ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Atmospheric Composition ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Measuring Instruments ◽  
Reference Spectrum ◽  
Vertical Column ◽  
Data Set ◽  
Residual Amount

Abstract. We present an algorithm for retrieving tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs) from ground-based zenith–sky (ZS) measurements of scattered sunlight. The method is based on a four-step approach consisting of (1) the differential optical absorption spectroscopy (DOAS) analysis of ZS radiance spectra using a fixed reference spectrum corresponding to low NO2 absorption, (2) the determination of the residual amount in the reference spectrum using a Langley-plot-type method, (3) the removal of the stratospheric content from the daytime total measured slant column based on stratospheric VCDs measured at sunrise and sunset, and simulation of the rapid NO2 diurnal variation, (4) the retrieval of tropospheric VCDs by dividing the resulting tropospheric slant columns by appropriate air mass factors (AMFs). These steps are fully characterized and recommendations are given for each of them. The retrieval algorithm is applied on a ZS data set acquired with a multi-axis (MAX-) DOAS instrument during the Cabauw (51.97° N, 4.93° E, sea level) Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI) held from 10 June to 21 July 2009 in the Netherlands. A median value of 7.9 × 1015 molec cm−2 is found for the retrieved tropospheric NO2 VCDs, with maxima up to 6.0 × 1016 molec cm−2. The error budget assessment indicates that the overall error σTVCD on the column values is less than 28%. In the case of low tropospheric contribution, σTVCD is estimated to be around 39% and is dominated by uncertainties in the determination of the residual amount in the reference spectrum. For strong tropospheric pollution events, σTVCD drops to approximately 22% with the largest uncertainties on the determination of the stratospheric NO2 abundance and tropospheric AMFs. The tropospheric VCD amounts derived from ZS observations are compared to VCDs retrieved from off-axis and direct-sun measurements of the same MAX-DOAS instrument as well as to data from a co-located Système d'Analyse par Observations Zénithales (SAOZ) spectrometer. The retrieved tropospheric VCDs are in good agreement with the different data sets with correlation coefficients and slopes close to or larger than 0.9. The potential of the presented ZS retrieval algorithm is further demonstrated by its successful application on a 2-year data set, acquired at the NDACC (Network for the Detection of Atmospheric Composition Change) station Observatoire de Haute Provence (OHP; Southern France).

scholarly journals On the relative absorption strengths of water vapour in the blue wavelength range

2015 ◽  
Vol 8 (6) ◽  
pp. 5895-5936 ◽  
Author(s):  
J. Lampel ◽  
D. Pöhler ◽  
J. Tschritter ◽  
U. Frieß ◽  
U. Platt
Keyword(s):  
Water Vapour ◽  
Cross Sections ◽  
Spectral Region ◽  
Field Measurements ◽  
Optical Absorption Spectroscopy ◽  
Absorption Cross ◽  
Absorption Bands ◽  
Blue Wavelength ◽  
Water Vapour Absorption ◽  
Density Ratios

Abstract. In recent updates of the HITRAN water vapour H2O spectroscopic compilation covering the blue spectral region (here: 394–480 nm) significant changes for the absorption bands at 416 and 426 nm were reported. In order to investigate the consistency of the different cross-sections calculated from these compilations, H2O vapour column density ratios for different spectral intervals were retrieved from Long-path and Multi-Axis – Differential Optical Absorption Spectroscopy (DOAS) measurements. We observed a significant improvement of the DOAS evaluation when using the updated HITRAN water vapour absorption cross-sections for the calculation of the reference spectra. In particular the magnitudes of the residual spectra as well as the fit errors were reduced. However we also found that the best match between measurement and model is reached when the absorption cross-section of groups of lines are scaled by factors ranging from 0.5 and 1.9, suggesting that the HITRAN water vapour absorption compilation still needs significant corrections. For this spectral region we present correction factors for HITRAN 2009, HITRAN 2012, HITEMP and BT2 derived from field measurements. Additionally, upper limits for water vapour absorption in the UV-A range from 330–390 nm are given.

scholarly journals An IBBCEAS system for atmospheric measurements of glyoxal and methylglyoxal in the presence of high NO<sub>2</sub> concentrations

2019 ◽  
Author(s):  
Jingwei Liu ◽  
Xin Li ◽  
Yiming Yang ◽  
Haichao Wang ◽  
Yusheng Wu ◽  
...  
Keyword(s):  
Cross Sections ◽  
Integration Time ◽  
Absorption Cross ◽  
Measurement Sensitivity ◽  
Atmospheric Measurements ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Spectrally Resolved ◽  
Spectra Fitting

Abstract. A system based on incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) has been developed for simultaneous measurement of nitrogen dioxide (NO2), glyoxal (GLY) and methylglyoxal (MGLY). On this system, the absorption of light around 460 nm is spectrally resolved. The concentration of absorbers is determined from a multi-component fit. At an integration time of 100 s, the measurement sensitivity (2σ) for NO2, GLY, and MGLY can reach 18 ppt, 30 ppt, and 100 ppt, respectively. The measurement uncertainty which mainly originates from path length calibration, sampling loss, and uncertainty of absorption cross sections is estimated to be 8 % for NO2, 8 % for GLY, and 16 % for MGLY. When applying the instrument during field observations, we found significant influence of NO2 on spectra fitting for retrieving GLY and MGLY concentration, which is caused by the fact that NO2 has higher absorption cross section and higher ambient concentration. In order to minimize such an effect, a NO2 photolytic convertor (NPC) which removes sampled NO2 at an efficiency of 76 % was integrated on the IBBCEAS system. Since sampled GLY and MGLY are mostly conserved (≥ 95 %) after passing through the NPC, the quality of the spectra fitting and the measurement accuracy of ambient GLY and MGLY were largely improved.

scholarly journals An IBBCEAS system for atmospheric measurements of glyoxal and methylglyoxal in the presence of high NO<sub>2</sub> concentrations

2019 ◽  
Vol 12 (8) ◽  
pp. 4439-4453 ◽  
Author(s):  
Jingwei Liu ◽  
Xin Li ◽  
Yiming Yang ◽  
Haichao Wang ◽  
Yusheng Wu ◽  
...  
Keyword(s):  
Cross Sections ◽  
Integration Time ◽  
Absorption Cross ◽  
Measurement Sensitivity ◽  
Atmospheric Measurements ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Spectrally Resolved ◽  
Spectra Fitting

Abstract. A system based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) has been developed for simultaneous measurement of nitrogen dioxide (NO2), glyoxal (GLY), and methylglyoxal (MGLY). In this system, the measured light absorption at around 460 nm is spectrally resolved. The concentration of absorbers is determined from a multicomponent fit. At an integration time of 100 s, the measurement sensitivity (2σ) for NO2, GLY, and MGLY is 18, 30, and 100 ppt, respectively. The measurement uncertainty, which mainly originates from path length calibration, sampling loss, and uncertainty of absorption cross sections is estimated to be 8 % for NO2, 8 % for GLY, and 16 % for MGLY. When deploying the instrument during field observations, we found significant influence of NO2 on the spectra fitting for retrieving GLY and MGLY concentrations, which is caused by the fact that NO2 has a higher absorption cross section and higher ambient concentration. In order to minimize such an effect, a NO2 photolytic convertor (NPC), which removes sampled NO2 at an efficiency of 76 %, was integrated on the IBBCEAS system. Since sampled GLY and MGLY are mostly (≥95 %) conserved after passing through the NPC, the quality of the spectra fitting and the measurement accuracy of ambient GLY and MGLY under NO2-rich environments could be improved.

scholarly journals Ground-based direct-sun DOAS and airborne MAX-DOAS measurements of the collision-induced oxygen complex, O<sub>2</sub>O<sub>2</sub>, absorption with significant pressure and temperature differences

2015 ◽  
Vol 8 (2) ◽  
pp. 793-809 ◽  
Author(s):  
E. Spinei ◽  
A. Cede ◽  
J. Herman ◽  
G. H. Mount ◽  
E. Eloranta ◽  
...  
Keyword(s):  
Cross Sections ◽  
Spectral Band ◽  
Specific Humidity ◽  
Optical Absorption Spectroscopy ◽  
Correction Factors ◽  
Absorption Cross ◽  
Atmospheric Conditions ◽  
Absorption Bands ◽  
Wide Range ◽  
Simultaneous Fitting

Abstract. The collision-induced O2 complex, O2O2, is a very important trace gas for understanding remote sensing measurements of aerosols, cloud properties and atmospheric trace gases. Many ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of the O2O2 optical depth require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a nearly pure Rayleigh atmosphere. One of the potential causes of this discrepancy is uncertainty in laboratory-measured O2O2 absorption cross section temperature and pressure dependencies due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents ground-based direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual atmospheric conditions in two wavelength regions (335–390 and 435–490 nm). DS irradiance measurements were made by the Washington State University research-grade Multi-Function Differential Spectroscopy Instrument instrument from 2007 to 2014 at seven sites with significant pressure (778 to 1013 hPa) and O2O2 profile-weighted temperature (247 to 275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado (CU) AMAX-DOAS instrument on 29 January 2012 over the Southern Hemispheric subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile-weighted temperatures of 231 to 244 K and nearly pure Rayleigh scattering conditions. Due to the well-defined DS air-mass factors during ground-based measurements and extensively characterized atmospheric conditions during the aircraft AMAX-DOAS measurements, O2O2 "pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2 column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the ground-based atmospheric DS observations, there is no pressure dependence of the O2O2 σ within the measurement errors (3%). Two data sets are combined to derive the peak σ temperature dependence of the 360 and 477 nm dimer absorption bands from 231 to 275 K. DS and AMAX-derived peak σ ( O2O2) as a function of T can be described by a quadratic function at 360 nm and linear function at 477 nm with about 9% ± 2.5% per 44 K rate. Recent laboratory-measured O2O2 cross sections by Thalman and Volkamer (2013) agree with these "DOAS apparent" peak σ( O2O2) at 233, 253 and 273 K within 3%. Changes in the O2O2 spectral band shape at colder temperatures are observed for the first time in field data. Temperature effects on spectral band shapes can introduce errors in the retrieved O2O2 column abundances if a single room temperature σ( O2O2) is used in the DOAS analysis. Simultaneous fitting of σ( O2O2) at temperatures that bracket the ambient temperature range can reduce such errors. Our results show that laboratory-measured σ( O2O2) (Hermans, 2011, at 296 K and Thalman and Volkamer, 2013) are applicable for observations over a wide range of atmospheric conditions. Column densities derived using Hermans (2011) σ at 296 K require very small correction factors (0.94 ± 0.02 at 231 K and 0.99 ± 0.02 at 275 K) to reproduce theoretically calculated slant column densities for DS and AMAX-DOAS measurements. Simultaneous fitting of σ( O2O2) at 203 and 293 K further improved the results at UV and visible wavelengths for AMAX-DOAS.

scholarly journals Detection of O<sub>4</sub> absorption around 328 nm and 419 nm in measured atmospheric absorption spectra

2017 ◽  
Author(s):  
Johannes Lampel ◽  
Johannes Zielcke ◽  
Stefan Schmitt ◽  
Denis Pöhler ◽  
Udo Frieß ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Spectral Data ◽  
Cross Section ◽  
Cross Sections ◽  
Trace Gases ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Absorption Cross ◽  
Peak Absorption ◽  
Spectrally Resolved

Abstract. Retrieving the column of an absorbing trace gas from spectral data requires that all absorbers in the corresponding wavelength range are sufficiently well known. This is especially important for the retrieval of weak absorbers, whose absorptions are often in the 10-4 range. Previous publications on the absorptions of the oxygen dimer O2-O2 (or short: O4) list absorption peaks at 328 nm and 419 nm, for which no spectrally resolved literature cross-sections are available. As these absorptions potentially influence the spectral retrieval of various trace gases, such as HCHO, BrO, OClO and IO, their shape and magnitude needs to be quantified. We assume that the shape of the absorption peaks at 328 nm and 419 nm can be approximated by their respective neighboring absorption peaks. Using this approach we obtain estimates for the wavelength of the absorption and its magnitude. Using Longpath Differential Optical Absorption Spectroscopy (LP-DOAS) observations and Multi-Axis (MAX)-DOAS observations, we estimate the peak absorption cross-sections of O4 to be (1.7 ± 0.2) x 10-47 cm5 molec-2 and determine the wavelength of its maximum at 328.51 ± 0.15 nm. For the absorption at 419.0 ± 0.4 nm a peak O4 cross-section value is determined as (3.7 ± 2.7) x 10-48 cm5 molec-2.

scholarly journals On the relative absorption strengths of water vapour in the blue wavelength range

2015 ◽  
Vol 8 (10) ◽  
pp. 4329-4346 ◽  
Author(s):  
J. Lampel ◽  
D. Pöhler ◽  
J. Tschritter ◽  
U. Frieß ◽  
U. Platt
Keyword(s):  
Water Vapour ◽  
Cross Sections ◽  
Spectral Region ◽  
Field Measurements ◽  
Optical Absorption Spectroscopy ◽  
Absorption Cross ◽  
Absorption Bands ◽  
Blue Wavelength ◽  
Water Vapour Absorption ◽  
Density Ratios

Abstract. In recent updates of the HITRAN water vapour H2O spectroscopic compilation covering the blue spectral region (here: 394–480 nm) significant changes for the absorption bands at 416 and 426 nm were reported. In order to investigate the consistency of the different cross-sections calculated from these compilations, H2O vapour column density ratios for different spectral intervals were retrieved from long-path and multi-axis differential optical absorption spectroscopy (DOAS) measurements. We observed a significant improvement of the DOAS evaluation when using the updated HITRAN water vapour absorption cross-sections for the calculation of the reference spectra. In particular the magnitudes of the residual spectra as well as the fit errors were reduced. However, we also found that the best match between measurement and model is reached when the absorption cross-section of groups of lines are scaled by factors ranging from 0.5 to 1.9, suggesting that the HITRAN water vapour absorption compilation still needs significant corrections. For this spectral region we present correction factors for HITRAN 2009, HITRAN 2012, HITEMP and BT2 derived from field measurements. Additionally, upper limits for water vapour absorption in the UV-A range from 330 to 390 nm are given.

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