 |
| Titel |
Lidar data assimilation for improved analyses of volcanic aerosol events |
| VerfasserIn |
Anne Caroline Lange, Hendrik Elbern |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091683
|
| Publikation (Nr.) |
 EGU/EGU2014-5987.pdf |
|
|
|
|
|
| Zusammenfassung |
| Observations of hazardous events with release of aerosols are hardly analyzable by today’s
data assimilation algorithms, without producing an attenuating bias. Skillful forecasts of
unexpected aerosol events are essential for human health and to prevent an exposure of infirm
persons and aircraft with possibly catastrophic outcome. Typical cases include mineral dust
outbreaks, mostly from large desert regions, wild fires, and sea salt uplifts, while the focus
aims for volcanic eruptions.
In general, numerical chemistry and aerosol transport models cannot simulate such events
without manual adjustments. The concept of data assimilation is able to correct the
analysis, as long it is operationally implemented in the model system. Though, the
tangent-linear approximation, which describes a substantial precondition for today’s
cutting edge data assimilation algorithms, is not valid during unexpected aerosol
events.
As part of the European COPERNICUS (earth observation) project MACC II and the national
ESKP (Earth System Knowledge Platform) initiative, we developed a module that enables the
assimilation of aerosol lidar observations, even during unforeseeable incidences of extreme
emissions of particulate matter. Thereby, the influence of the background information has to
be reduced adequately.
Advanced lidar instruments comprise on the one hand the aspect of radiative transfer within
the atmosphere and on the other hand they can deliver a detailed quantification of the detected
aerosols. For the assimilation of maximal exploited lidar data, an appropriate lidar
observation operator is constructed, compatible with the EURAD–IM (European Air
Pollution and Dispersion – Inverse Model) system. The observation operator is able to map
the modeled chemical and physical state on lidar attenuated backscatter, transmission, aerosol
optical depth, as well as on the extinction and backscatter coefficients. Further, it has the
ability to process the observed discrepancies with lidar data in a variational data assimilation
algorithm.
The implemented method is tested by the assimilation of CALIPSO attenuated backscatter
data that were taken during the eruption of the Eyjafjallajökull volcano in April 2010. It
turned out that the implemented module is fully capable to integrate unexpected aerosol
events in an automatic way into reasonable analyses. The estimations of the aerosol mass
concentrations showed promising properties for the application of observations that are
taken by lidar systems with both, higher and lower sophistication than CALIOP. |
|
|
|
|
|
|