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Use of Lidar Backscatter to Determine the PBL Heights in New York City, NY

Use of Lidar Backscatter to Determine the PBL Heights in New York City, NY. Jia-Yeong Ku, Chris Hogrefe, Gopal Sistla New York State Department of Environmental Conservation Albany, NY 12233 And Shuki Chaw, Leona Charles, Barry Gross City College of City University of New York

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Use of Lidar Backscatter to Determine the PBL Heights in New York City, NY

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  1. Use of Lidar Backscatter to Determine the PBL Heights in New York City, NY Jia-Yeong Ku, Chris Hogrefe, Gopal Sistla New York State Department of Environmental Conservation Albany, NY 12233 And Shuki Chaw, Leona Charles, Barry Gross City College of City University of New York New York, NY 10031

  2. Objective • Analyze Lidar Backscatter to determine PBL Heights using Wavelet method • Demonstrate the potential of applying Lidar Backscatter in the air quality forecast evaluation

  3. Data • Lidar measured backscatter signal • PBL heights and aerosol extinction coefficients out of WRF/CMAQ air quality forecast system

  4. Lidar System • Lidar (Light Detection And Range) measures the intensity of backscattered light as a function of distance • The primary contribution of scattering is from aerosol particles suspended in the air

  5. Lidar Backscatter C: calibration constant β: backscatter coefficient α: extinction coefficient

  6. CCNY Lidar Setup Lidar data: 1064 nm channel Temporal resolution: 1 minute Vertical resolution: 37.5 m

  7. WRF/CMAQ Forecast System • Meteorology/Emission: Based on NECP/NWS 48-hr WRF forecasts initialized at 12:00 UTC and 2002/2004 emission inventory, processed with PREMAQ • Photochemical Model: CMAQ (ver 4.51) Horizontal resolution: 12 km vertical resolution: 22 layers, lowest layer ~40 m • Study periods: July 31 – August 2, 2006

  8. EDST Location: National Weather Service (NWS) NWS Eta for CMAQ 22 sigma layer, 12 km, Lambert-Conformal NWS Product Generator (horizontal interpolation) NWS Eta 12km 48hr Forecast Initialized at 12:00 UTC NWS Eta-Post (vertical interpolation) 08:00 10:00 NWS CMAQ-Eta 12km O3 forecasts for Northeast (NE) domain 13:00 EPA stores emission input files at EPA NESC 18:00 EPA gets Eta for CMAQ to EPA NESC EPA gets NOAA AQ forecasting output (NE domain) and archives at EPA NESC 20:00 NYSDEC runs PREMAQ at EPA NESC to generate model-ready meteorology and emissions 21:00 Location: EPA RTP Atmospheric Modeling Division National Environmental Supercomputing Center (NESC) NYSDEC brings PREMAQ output (model-ready emissions and meteorology) back to their Linux cluster 23:00 Location: NY State Department of Environmental Conservation (NYSDEC) 01:00 NYSDEC runs CMAQ using PREMAQ model-ready emissions and meteorology for near-realtime O3 and PM forecasts on NYSDEC Aspen Linux Cluster. Postprocessing finishes by 05:30 EDST Research Mode: Run alternate CMAQ version from 5.30 to 9.30 EDST 05:30

  9. Modeling Domain

  10. Analyze Lidar Backscatter for PBL Heights • Boundary layer usually has much higher aerosol concentration than free troposphere above. • The significant change in the backscatter across the top of the BL provides a means of determining PBL heights. • Wavelet provides a scale-dependent approach to determine PBL height.

  11. Wavelet Covariance Transform

  12. The key of the wavelet analysis is the selection of an appropriate dilation (vertical scale).

  13. Compare PBL heights of Lidar measured and Model predicted • Lidar measures aerosol layers • Model determines vertical mixing based on some meteorological parameters, such as temperature and wind field

  14. Compare Lidar Backscatter and CMAQ Extinction Coefficient • Hourly and vertical averaged Lidar Backscatter signal • Hourly extinction coefficient of CMAQ outputs • A qualitative comparison; both backscatter and extinction coefficient reflect the aerosol and humidity loading in the atmosphere

  15. July 31, 2006

  16. August 1, 2006

  17. August 2, 2006

  18. Summary • A wavelet technique is applied to analyze the PBL height using lidar backscatter measured in New York City • WRF/CMAQ forecast system keeps track the lidar measured PBL development well • WRF/CMAQ forecast system predicted the vertical PM profile (in terms of extinction coefficient) resemble to the backscatter vertical profile under cloud free conditions • Development in the areas that we can directly compare the aerosol optical products between Lidar and model.

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