 |
| Titel |
Retrieval of volcanic plume aerosol properties from UV-spectroscopic DOAS measurements |
| VerfasserIn |
Christoph Kern, Nicole Bobrowski, Tim Deutschmann, Leif Vogel, Markus Wöhrbach, Thomas Wagner, Ulrich Platt |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041079
|
|
|
|
|
|
| Zusammenfassung |
| Passive differential optical absorption spectroscopy (DOAS) has become a standard tool for
the quantification of SO2 emission fluxes from volcanoes. However, this measurement
technique has the potential to measure not only trace gas absorption but also some
aerosol properties of volcanic plumes. In fact, recent model studies have shown
that knowledge of the plume’s aerosol optical depth is important for the retrieval
of accurate SO2 column densities, as multiple scattering of radiation on aerosol
particles in a plume can lead to a significant enhancement of the measured SO2
absorption signal. In this presentation, a retrieval scheme is presented that combines
radiative transfer modelling with spectral analysis of DOAS measurements in the
ultra-violet spectral region to simultaneously retrieve accurate SO2 column densities
and aerosol optical depths. A three-dimensional backward Monte Carlo radiative
transfer model is used to simulate measurement spectra that would be obtained for a
certain physical state of the atmosphere and volcanic plume. Thus, a solution to the
forward problem is obtained. By varying the state vector until the simulations match
the remote sensing observations, this problem can be inverted using a standard
Levenberg-Marquardt algorithm. We show here that the information content of the
measurement is sufficient to allow an unambiguous inversion of both, the aerosol optical
depth and SO2 column. The method is then tested on a number of different scenarios and the
potential and limitations of the algorithms are explored. By applying this novel retrieval
technique to DOAS measurements from ground-based and satellite platforms, the
accuracy of UV-spectroscopic measurements of SO2 in volcanic plumes can be greatly
enhanced while at the same time allowing an accurate retrieval of aerosol conditions. |
|
|
|
|
|
|