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Evaluation of WRF-Chem Model Forecasts of a Prolonged Sahara Dust Episode over the Eastern Alps

Category: Air Pollution Modeling

Accepted Manuscripts
DOI: 10.4209/aaqr.2018.03.0116
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Kathrin Baumann-Stanzer1, Marion Greilinger1, Anne Kasper-Giebl2, Claudia Flandorfer1, Alexander Hieden1, Christoph Lotteraner1, Martin Ortner3, Johannes Vergeiner4, Gerhard Schauer5, Martin Piringer1

  • 1 Central Institute for Meteorology and Geodynamics (ZAMG), 1190 Vienna, Austria
  • 2 Institute of Chemical Technologies and Analytics, Vienna University of Technology, 1060 Vienna, Austria
  • 3 ZAMG Customer Service Carinthia, 9020 Klagenfurt, Austria
  • 4 ZAMG Customer Service Tyrol and Vorarlberg, 6020 Innsbruck, Austria
  • 5 ZAMG Customer Salzburg and Upper Austria, 5020 Salzburg, Austria

Highlights

Daily mean PM concentrations highest at mountain tops with south-westerly flow.
Sahara dust cloud leading to maximum PM values at Eastern Alps in early April 2016.
Ceilometer observe descending dust cloud from above into atmospheric boundary layer.
WRF-Chem successfully forecasts on-set, maximum concentrations and end of event.
FLEXPART backwards used to estimate proportion of air from Sahara sub-regions.


Abstract

Sahara dust transport causes a substantial natural background to particle matter concentrations in Central Europe. The contributions by Sahara dust are especially well detectable at Alpine mountain sites where many other sources have minor impact. The ability of a chemical weather forecast model to simulate dust transport correctly is of vital interest as there might be cases of serious health effects for the population which may require countermeasures, as with nuclear or industrial accidents, wildfires, pollen, etc. Here we investigate whether the WRF-Chem set-up, which is run operationally for air quality forecasts in Austria, is able to forecast the transport of the Saharan dust cloud in April 2016 towards Central Europe correctly. WRF-Chem simulations with and without desert dust emissions reveal that 60 to 70% of the dust arriving at the Eastern Alps originate from desert dust emissions whenever PM concentrations are high during the three periods of this event. The measurements and model results deliver a detailed picture of the course of this extraordinary dust event with successive peaks over the Eastern Alpine region. By the presented example of the analysis of a long-lasting Sahara dust event, a structured approach is proposed to step-wise investigate dust peak episodes based on data analysis of representative background sites, source area analysis by means of Lagrangian dispersion modelling as well as based on coupled meteorological and chemistry modelling.

Keywords

Saharan dust Long-range transport WRF-Chem model FLEXPART model Source-receptor sensitivity Ceilometer


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Accepted Manuscripts
DOI: 10.4209/aaqr.2018.09.0344
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