scholarly journals Formaldehyde total column densities over Mexico City: comparison between multi-axis differential optical absorption spectroscopy and solar-absorption Fourier transform infrared measurements

2021 ◽  
Vol 14 (1) ◽  
pp. 595-613
Author(s):  
Claudia Rivera Cárdenas ◽  
Cesar Guarín ◽  
Wolfgang Stremme ◽  
Martina M. Friedrich ◽  
Alejandro Bezanilla ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Optical Absorption ◽  
Mexico City ◽  
Absorption Spectroscopy ◽  
Fourier Transform Infrared ◽  
Differential Optical Absorption Spectroscopy ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Solar Absorption ◽  
Total Column

Abstract. Formaldehyde (HCHO) total column densities over the Mexico City metropolitan area (MCMA) were retrieved using two independent measurement techniques: multi-axis differential optical absorption spectroscopy (MAX-DOAS) and Fourier transform infrared (FTIR) spectroscopy. For the MAX-DOAS measurements, the software QDOAS was used to calculate differential slant column densities (dSCDs) from the measured spectra and subsequently the Mexican MAX-DOAS fit (MMF) retrieval code to convert from dSCDs to vertical column densities (VCDs). The direct solar-absorption spectra measured with FTIR were analyzed using the PROFFIT (PROFile FIT) retrieval code. Typically the MAX-DOAS instrument reports higher VCDs than those measured with FTIR, in part due to differences found in the ground-level sensitivities as revealed from the retrieval diagnostics from both instruments, as the FTIR and the MAX-DOAS information do not refer exactly to the same altitudes of the atmosphere. Three MAX-DOAS datasets using measurements conducted towards the east, west or both sides of the measurement plane were evaluated with respect to the FTIR results. The retrieved MAX-DOAS HCHO VCDs where 6 %, 8 % and 28 % larger than the FTIR measurements which, supported with satellite data, indicates a large horizontal inhomogeneity in the HCHO abundances. The temporal change in the vertical distribution of this pollutant, guided by the evolution of the mixing-layer height, affects the comparison of the two retrievals with different sensitivities (total column averaging kernels). In addition to the reported seasonal and diurnal variability of HCHO columns within the urban site, background data from measurements at a high-altitude station, located only 60 km away, are presented.

scholarly journals Formaldehyde total column densities over Mexico City: comparison between MAX-DOAS and solar absorption FTIR measurements

2020 ◽  
Author(s):  
Claudia Rivera Cárdenas ◽  
Cesar Guarín ◽  
Wolfgang Stremme ◽  
Martina M. Friedrich ◽  
Alejandro Bezanilla ◽  
...  
Keyword(s):  
Mexico City ◽  
Measurement Techniques ◽  
Mixing Layer ◽  
Ground Level ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Solar Absorption ◽  
Diurnal Variability ◽  
Total Column

Abstract. Formaldehyde (HCHO) total column densities over the Mexico City Metropolitan Area (MCMA) were retrieved using two independent measurement techniques: Multi Axis – Differential Optical Absorption Spectroscopy (MAX-DOAS) and Fourier Transform Infrared (FTIR) Spectroscopy. For the MAX-DOAS measurements, the software QDOAS was used to calculate differential Slant Column Densities (dSCDs) from the measured spectra and subsequently the Mexican MAX-DOAS Fit retrieval code (MMF) to convert from dSCDs to Vertical Column Densities (VCDs). The direct-solar absorption spectra measured with FTIR were analyzed using the PROFFIT retrieval code. Typically the MAX-DOAS instrument reports higher VCDs than those measured with FTIR, in part due to differences found in the ground-level sensitivities as revealed from the retrieval diagnostics from both instruments. Three MAX-DOAS datasets using measurements conducted towards the east, west or both sides of the measurement plane were evaluated with respect to the FTIR results. The retrieved MAX-DOAS HCHO VCDs where 5 %, 9 % and 28 % larger than the FTIR which, supported with satellite data, could demonstrate a large horizontal inhomogeneity in the HCHO abundances. A time-dependent comparison revealed that the vertical distribution of this pollutant, guided by the evolution of the mixing layer height, can play an important role in how the results are affected. Apart from the reported seasonal and diurnal variability of HCHO columns within the urban site, background data from measurements at a high-altitude station, located only 60 km away are presented.

Measurement of SO2 Using Differential Optical Absorption Spectroscopy Based Fourier Transform Filtering

2012 ◽  
Vol 571 ◽  
pp. 234-238
Author(s):  
Hai Ming Zheng ◽  
Zhen Liang Dong ◽  
Dong Shui Xie ◽  
Xiao Xiao Shang
Keyword(s):  
Fourier Transform ◽  
Optical Absorption ◽  
Least Squares ◽  
Absorption Spectroscopy ◽  
Least Squares Method ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Atmospheric Species ◽  
The Fourier Transform ◽  
The Way

Differential Optical Absorption Spectroscopy(DOAS) is widely used to determine concentrations of atmospheric species. This paper makes a measurement of SO2 using DOAS based on LabVIEW, and compare the concentrations retrieved by the least squares method and the way of Fourier transform filtering. Experiment results indicate that the Fourier transform filtering is superior to the least squares method for monitoring a single SO2 ingredients.

scholarly journals Total Ozone Columns from the Environmental Trace Gases Monitoring Instrument (EMI) Using the DOAS Method

2021 ◽  
Vol 13 (11) ◽  
pp. 2098
Author(s):  
Yuanyuan Qian ◽  
Yuhan Luo ◽  
Fuqi Si ◽  
Haijin Zhou ◽  
Taiping Yang ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Total Ozone ◽  
Scattered Light ◽  
Trace Gases ◽  
Rapid Change ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Monitoring Instrument ◽  
Monthly Average

Global measurements of total ozone are necessary to evaluate ozone hole recovery above Antarctica. The Environmental Trace Gases Monitoring Instrument (EMI) onboard GaoFen 5, launched in May 2018, was developed to measure and monitor the global total ozone column (TOC) and distributions of other trace gases. In this study, some of the first global TOC results of the EMI using the differential optical absorption spectroscopy (DOAS) method and validation with ground-based TOC measurements and data derived from Ozone Monitoring Instrument (OMI) and TROPOspheric Monitoring Instrument (TROPOMI) observations are presented. Results show that monthly average EMI TOC data had a similar spatial distribution and a high correlation coefficient (R ≥ 0.99) with both OMI and TROPOMI TOC. Comparisons with ground-based measurements from the World Ozone and Ultraviolet Radiation Data Centre also revealed strong correlations (R > 0.9). Continuous zenith sky measurements from zenith scattered light differential optical absorption spectroscopy instruments in Antarctica were also used for validation (R = 0.9). The EMI-derived observations were able to account for the rapid change in TOC associated with the sudden stratospheric warming event in October 2019; monthly average TOC in October 2019 was 45% higher compared to October 2018. These results indicate that EMI TOC derived using the DOAS method is reliable and has the potential to be used for global TOC monitoring.

scholarly journals Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range

2007 ◽  
Vol 7 (1) ◽  
pp. 69-79 ◽  
Author(s):  
T. Wagner ◽  
S. Beirle ◽  
T. Deutschmann ◽  
M. Grzegorski ◽  
U. Platt
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Spectral Range ◽  
Near Infrared ◽  
Vegetation Type ◽  
Differential Optical Absorption Spectroscopy ◽  
Trace Gas ◽  
Satellite Monitoring ◽  
Optical Absorption Spectroscopy ◽  
Vegetation Types

Abstract. A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms). The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

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