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

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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

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Objective

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

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Data

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

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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

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Lidar Backscatter
C calibration constant ß backscatter
coefficient a extinction coefficient
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CCNY Lidar Setup
Lidar data 1064 nm channel Temporal resolution
1 minute Vertical resolution 37.5 m
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WRF/CMAQ Forecast System

• Meteorology/Emission Based on NECP/NWS 48-hr WRF
  forecasts initialized at 1200 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

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EDST
NWS Eta for CMAQ 22 sigma layer, 12
km, Lambert-Conformal
NWS Eta 12km 48hr Forecast Initialized at 1200
UTC
NWS Product Generator (horizontal interpolation)
NWS Eta-Post (vertical interpolation)
0800
1000
NWS CMAQ-Eta 12km O3 forecasts for Northeast (NE)
domain
1300
EPA stores emission input files at EPA NESC
1800
EPA gets Eta for CMAQ to EPA NESC
EPA gets NOAA AQ forecasting output (NE domain)
and archives at EPA NESC
2000
NYSDEC runs PREMAQ at EPA NESC to generate
model-ready meteorology and emissions
2100
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
2300
Location NY State Department of Environmental
Conservation (NYSDEC)
0100
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 0530 EDST Research
Mode Run alternate CMAQ version from 5.30 to
9.30 EDST
0530
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Modeling Domain
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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.

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

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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

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July 31, 2006
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August 1, 2006
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August 2, 2006
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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.