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The Impact of Various Data Sources on Forecasting the Coastal Atmospheric Environment: The 2004 Athens Olympics

The Impact of Various Data Sources on Forecasting the Coastal Atmospheric Environment: The 2004 Athens Olympics. Andrea Hahmann Yubao Liu Thomas Warner NCAR Research Applications Lab. BACIMO, Oct 13 2005. Contributors to Athens local circulation.

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The Impact of Various Data Sources on Forecasting the Coastal Atmospheric Environment: The 2004 Athens Olympics

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  1. The Impact of Various Data Sources on Forecasting the Coastal Atmospheric Environment: The 2004 Athens Olympics Andrea Hahmann Yubao Liu Thomas Warner NCAR Research Applications Lab. BACIMO, Oct 13 2005

  2. Contributors to Athens local circulation Unique Aegean geography makes the Athens basin particularly challenging to forecast accurately Etesian winds flush contaminants from urban areas Sea breezes can instead concentrate contaminants in those areas BACIMO, October 2005

  3. Research Objectives Real-time operational mesoscale simulations conducted during the 2004 Summer Olympic Games Sponsored by Defense Threat Reduction Agency (DTRA), focus on consequence assessment during the games • Study the “added value” of mesoscale forcings provided by high resolution : • land surface characteristics • sea surface temperatures • topography • representation of sea-land contrasts (orientation of coastline) BACIMO, October 2005

  4. Modeling system MM5 based modeling system, including nudging of observations (FDDA) 30 km, 3 nests (10, 3.3, and 1.1 km) BACIMO, October 2005

  5. MM5 model land-use/vegetation distribution Real-time FDDA and forecasts August 12-September 16, 2004 Large MODIS-derived urban region over Metropolitan Athens BACIMO, October 2005

  6. Model Boundary Conditions: Sea surface temperatures Sea surface temperature analysis provided by: Mediterranean Forecasting System Toward Environmental Predictions (MFSTEP), Bologna, Italy Weekly 1/8° analysis (forecast SST also available) BACIMO, October 2005

  7. Verification of surface analysis and forecasts Real time data from surface stations provided by the University of Athens BACIMO, October 2005

  8. Domain-averaged bias and RMSE as a function of model domain (1-4) interior domain Statistics for all MM5 forecasts started at 2300 UTC period: 12 August - 16 September 2004 BACIMO, October 2005

  9. --- Observations --- Model (closest grid point) 13 hour forecast FDDA (analysis) Period: 12 August - 12 Sept 2004 valid at 1200 UTC (1500 LST) BACIMO, October 2005

  10. Case studies: strategy • Select 2-3 cases of strong breeze, weak breeze, and Etesian flow • Run 24 hour FDDA cycle for day-1 • Run 36 hour free forecast with “best” available boundary conditions and model set-up • “Degrade” lower boundary and/or initial conditions to investigate their relative importance to the forecast quality (as verified by surface observations) BACIMO, October 2005

  11. First sensitivity experiment: replace urban area Urban zone replaced by native vegetation (shrubland) in domain 4 only BACIMO, October 2005

  12. Surface energy balance over urban area 2-m temperature URBAN FDDA NOURBAN Average region Latent heat flux NOURBAN First 18 hours: analysis; free FCST after URBAN FDDA BACIMO, October 2005

  13. Sea breeze circulation under modified surface conditions (NOURBAN - CONTROL) Further inland penetration of the “breeze front” Stronger winds over urban area first-level temperature differences (K) BACIMO, October 2005

  14. High resolution topography, vegetation/land use, and boundary conditions (SSTs) are crucial to an accurate representation of the low-level circulation over Athens, Greece during the summer season. In the experiment where the urban zone was removed stronger winds occur over the area, and the sea breeze penetrates further inland and/or earlier than in the control simulation. The urban friction effect appears to overcompensate the UHI effect, which leads to an overall blocking effect to the sea breeze development. Extend experiments to cases dominated by weak breeze and Etesian winds Future experiments will examine the sensitivity to: Sea surface temperatures (global analysis versus high resolution SSTs) Assimilation of surface observation during the FDDA portion of the experiments Reduced elevation of the local topography Summary & Future Work BACIMO, October 2005

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