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Extending Differential Optical Absorption Spectroscopy for Limb Measurements in the Uv : Volume 2, Issue 6 (18/11/2009)

By Puķīte, J.

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Book Id: WPLBN0003975640
Format Type: PDF Article :
File Size: Pages 64
Reproduction Date: 2015

Title: Extending Differential Optical Absorption Spectroscopy for Limb Measurements in the Uv : Volume 2, Issue 6 (18/11/2009)  
Author: Puķīte, J.
Volume: Vol. 2, Issue 6
Language: English
Subject: Science, Atmospheric, Measurement
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2009
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Puķīte, J., Wagner, T., Deutschmann, T., Kühl, S., & Platt, U. (2009). Extending Differential Optical Absorption Spectroscopy for Limb Measurements in the Uv : Volume 2, Issue 6 (18/11/2009). Retrieved from http://hawaiilibrary.net/


Description
Description: Max Planck Institute for Chemistry, J. J. Becher Weg 27, 55128 Mainz, Germany. Methods of UV/VIS absorption spectroscopy to determine the constituents in the Earth's atmosphere from measurements of scattered light are often based on the Beer-Lambert law, like e.g. Differential Optical Absorption Spectroscopy (DOAS). Therefore they are strictly valid for weak absorptions and narrow wavelength intervals (strictly only for monochromatic radiation). For medium and strong absorption (e.g. along very long light-paths like in limb geometry) the relation between the optical depth and the concentration of an absorber is not linear anymore. As well, for large wavelength intervals the wavelength dependent differences in the travelled light-paths become important, especially in the UV, where the probability for scattering increases strongly with decreasing wavelength.

However, by taking into account these dependencies, the applicability of the DOAS method can be extended also to cases with medium to strong absorptions and for broader wavelength intervals.

Common approaches for this correction are the so called air mass factor modified (or extended) DOAS and the weighting function modified DOAS. These approaches take into account the wavelength dependency of the slant column densities (SCDs), but also require a-priori knowledge for the air mass factor or the weighting function calculation by radiative transfer modelling.

We describe an approach that considers the fitting results obtained from DOAS, the SCDs, as a function of wavelength and vertical optical depth and expands this function into a Taylor series of both quantities. The Taylor coefficients are then applied as additional fitting parameters in the DOAS analysis. Thus the variability of the SCD in the fit window is determined by the retrieval itself.

This new approach gives a description of the SCD that is as close to reality as desired (depending on the order of the Taylor expansion), and is independent from any assumptions or a-priori knowledge of the considered absorbers.

In case studies for simulated and measured spectra in the UV (332–357 nm), we demonstrate the improvement by this approach for the retrieval of vertical profiles of BrO from the SCIAMACHY limb observations. Compared to the standard DOAS approach, the results for BrO obtained from the simulated spectra are closer to the true profile, when applying the new method for the SCDs of ozone. Also for the measured spectra the agreement with validation measurements is improved significantly, especially for cases with strong ozone absorption.

While the focus of this article is on the improvement of the BrO profile retrieval from the SCIAMACHY limb measurements, the novel approach may be applied for a wide range of DOAS retrievals.


Summary
Extending differential optical absorption spectroscopy for limb measurements in the UV

Excerpt
Bovensmann, H., Burrows, J. P., Buchwitz, M., Frerick, J., Noël, S., Rozanov, V. V., Chance, K. V., and Goede, A. P. H.: SCIAMACHY: Mission objectives and measurement modes, J. Atmos. Sci., 56, 127–150, 1999.; Brewer, A. W., McElroy, C. T., and Kerr, J. B.: Nitrogen dioxide concentrations in the atmosphere, Nature, 246, 129–133, 1973.; Buchwitz, M., Rozanov, V. V., and Burrows, J. P.: A near-infrared optimized DOAS method for the fast global retrieval of atmospheric CH4, CO, CO2, H2O, and N2O total column amounts from SCIAMACHY Envisat-1 nadir radiances, J. Geophys. Res., 105(D12), 15231�-15245, 2000.; Burrows, J. P., Weber, M., Buchwitz, M., Rozanov, V., Ladstätter-Weiß{}enmayer, A., Richter, A., Debeek, R., Hoogen, R., Bramstedt, K., Eichmann, K.-U., Eisinger, M., and Perner, D.: The Global Ozone Monitoring Experiment (GOME): Mission Concept and First Scientific Results, J. Atmos. Sci., 56, 151–171, 1999.; Butz, A., Bösch, H., Camy-Peyret, C., Chipperfield, M., Dorf, M., Dufour, G., Grunow, K., Jeseck, P., Kühl, S., Payan, S., Pepin, I., Pukite, J., Rozanov, A., von Savigny, C., Sioris, C., Wagner, T., Weidner, F., and Pfeilsticker, K.: Inter-comparison of stratospheric O3 and NO2 abundances retrieved from balloon borne direct sun observations and Envisat/SCIAMACHY limb measurements, Atmos. Chem. Phys., 6, 1293–1314, 2006.; Coldewey-Egbers, M., Weber, M., Buchwitz, M., and Burrows, J. P.: Application of a modified DOAS method for total ozone retrieval from GOME data at high polar latitudes, Adv. Space Res., 34, 749–753, doi:10.1016/j.asr.2003.05.051, 2004.; Coldewey-Egbers, M., Weber, M., Lamsal, L. N., de Beek, R., Buchwitz, M., and Burrows, J. P.: Total ozone retrieval from GOME UV spectral data using the weighting function DOAS approach, Atmos. Chem. Phys., 5, 1015–1025, 2005.; Deutschmann, T.: Atmospheric radiative transfer modelling using Monte Carlo methods, Diploma Thesis, Universität Heidelberg, 2009.; Diebel, D., de Beek, R., Burrows, J. P., Kerridge, B., Munro, R., Platt, U., Marquard, L., and Muirhead, K.: Trace gas study: Detailed analysis of the retrieval algorithms selected for the level 1–2 processing of GOME data, Tech. Rep., Eur. Space Agency (ESA), Section 5, 5–150 pp., 1995.; Dorf, M., Bösch, H., Butz, A., Camy-Peyret, C., Chipperfield, M. P., Engel, A., Goutail, F., Grunow, K., Hendrick, F., Hrechanyy, S., Naujokat, B., Pommereau, J.-P., Van Roozendael, M., Sioris, C., Stroh, F., Weidner, F., and Pfeilsticker, K.: Balloon-borne stratospheric BrO measurements: comparison with Envisat/SCIAMACHY BrO limb profiles, Atmos. Chem. Phys., 6, 2483–2501, 2006.; Dorf, M., Butz, A., Camy-Peyret, C., Chipperfield, M. P., Kritten, L., and Pfeilsticker, K.: Bromine in the tropical troposphere and stratosphere as derived from balloon-borne BrO observations, Atmos. Chem. Phys., 8, 7265–7271, 2008.; Fleischmann, O. C., Hartmann, M., Burrows, J. P., and Orphal, J.: New ultraviolet absorption cross-sections of BrO at atmospheric temperatures measured by time-windowing Fourier transform spectroscopy, J. Photoch. Photobio. A, 168, 117-�132, 2004.; Frankenberg, C., Platt, U., and Wagner, T.: Iterative maximum a posteriori (IMAP)-DOAS for retrieval of strongly absorbing trace gases: Model studies for CH4 and CO2 retrieval from near infrared spectra of SCIAMACHY onboard ENVISAT, Atmos. Chem. Phys., 5, 9–22, 2005.; Kühl, S.: Quantifying Stratospheric chlorine chemistry by the satellite spectrometers GOME and SCIAMACHY, PhD Thesis, Universität Heidelberg, Heidelberg, Germany, available at: http://www.ub.uni-heidelberg.de/archiv/5664/, 177 pp.,2005.; Kühl, S., Puķ\=ıte, J., Deutschmann, T., Platt, U., an

 

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