Office of Research and Development Atmospheric Modeling and Analysis Division, National Exposure Research Laboratory Improved Treatment of Boundary Layers in Urban Areas for Air Quality Modeling. Jonathan Pleim and Robert Gilliam USEPA
Improved Treatment of Boundary Layers in Urban Areas for Air Quality Modeling.
Jan 12, 2016
Improved Treatment of Boundary Layers in Urban Areas for Air Quality Modeling. . Jonathan Pleim and Robert Gilliam USEPA. Motivation. Urban/suburban areas are generally warmer and more turbulent than surroundings - PowerPoint PPT Presentation
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Office of Research and DevelopmentAtmospheric Modeling and Analysis Division, National Exposure Research Laboratory
Improved Treatment of Boundary Layers in Urban Areas for Air Quality Modeling. Jonathan Pleim and Robert Gilliam USEPA
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Motivation• Urban/suburban areas are generally warmer and more
turbulent than surroundings• Less stable boundary layers at night and during morning
and evening transitions mix surface emissions more quickly• Rate of morning PBL growth and entrainment from residual
layers are critical for photochemisty in urban areas• Effects of built environments disproportionately important
for AQ because of high emissions in these areas
2
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Problem
• Without realistic treatment of UHI:–PBL too stable during
morning and evening transitions and overnight
–Overprediction of ground emitted primary species (e.g. CO, NOx, Primary PM)
July 2006 – CMAQ 12 km CO
Birmingham (SEARCH)
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
304 306 308 310 312 314
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ThetaTheta
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4 km modeling for Houston – August 2006
WRF Potential temperature (blue) in Houston at 7 PM shows premature surface inversion
CMAQ v4.7 and 5.0 overpredict CO especially during morning and evening rush hours
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Potential Solutions
• Meteorological models and parameterizations for urban areas vary greatly in complexity and data requirements.• Currently WRF has several urban parameterizations: Bulk,
single-layer, and multi-level BEP-BEM NUDAPT all tied to the NOAH LSM• Need for a simple scheme considers the effects of
development at the local (1-4 km) and regional (12 km) grid scales that works with the PX LSM that we use for WRF-CMAQ.
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
A New Bulk Approach for PX LSM• Leverage very high resolution National Land Cover Database
(NLCD) with multi-level urban classifications –PX LSM considers subgrid LU fractions
• Utilize NLCD-based Impervious surface data directly in land-surface model to scale surface heat capacity• Increase surface roughness for urban LU classes to better
represent developed areas• Decrease albedo in urbanized areas to account for sky-view
and radiation trapping effects• Reduce deep soil temperature nudging strength
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
7
Impervious Fraction (%) for 12 km Grid
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
8
Impervious Fraction (%) for 4km Grid
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
9
Impervious Fraction (%) for 1 km Grid
Shopping malls in Sugarland
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Skin Temperature on Aug 24,2006 at 10Z
10
Base – NLCD 2006 Impervious 2
Evaluation Using Tethersonde ProfilesTethersondes were launched on selected evening and nights in September through November at U of Houston
Profiles from 2 model runs :NoImp --- no impervious, NLCD 2006
Imp2 – Impervious, increased roughness, decreased albedo and weaker deep soil temp nudging
Tethersonde data provided by Bernhard Rappenglueck (UH)
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 7, 20 LT (1Z)
302.5 303 303.5 304 304.5
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qv
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Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 7, 23LT (4Z)
300 300.5 301 301.5 302 302.5 303 303.5 304
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Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 7, Midnight LT (5Z)
0 1 2 3 4 5 6
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WS-noimpWS-imp2Tethersonde
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299.5 300 300.5 301 301.5 302 302.5 303 303.5
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wrf_9-8_noimpout
Theta-noimpTheta-imp2Tethersonde
Theta-noimp
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 8, 2LT (7Z)
298 299 300 301 302 303 304
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Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 8, 3LT (8Z)
298 299 300 301 302 303 304
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Tethersonde
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wrf_9-8_noimpout
WS-noimpWS-imp2Tethersonde
WS-noimp
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 8, 4LT (9Z)
297 298 299 300 301 302 303 304
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wrf_9-8_noimpout
Theta-noimpTheta-imp2Tethersonde
Theta-noimp
-1 0 1 2 3 4 5
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wrf_9-8_noimpout
WS-noimpWS-imp2Tethersonde
WS-noimp
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 8, 6LT (11Z)
297 298 299 300 301 302 303
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wrf_9-8_noimpout
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Theta-noimp
0 1 2 3 4 5 6 7 8
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WS-noimpWS-imp2Tethersonde
WS-noimp
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
September 8, 8LT (13Z)
296 297 298 299 300 301 302 303
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1 2 3 4 5 6 7 8
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wrf_9-8_noimpout
WS-noimpWS-imp2Tethersonde
WS-noimp
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Effects of urban scheme on AQ modeling
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11 12 13 14 15 16 17 18 19 20 21 22 23 24
OBS_CONOIMPERV_COIMPERV1_COIMPERV2_CO
Hour (GMT)
These preliminary experiments show modest reduction of CO overprediction
Average CO over AQS sites in Houston for 5 days
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Conclusions• New bulk urban scheme for the PX-LSM shows much
improved PBL structure in evening, overnight, and morning compared to Houston tethersonde measurements• Designed to take advantage of hi-resolution NLCD LU data
and impervious surface area.• The capability of the PX LSM to include subgrid LU fractions
and any amount of impervious surface allows effects of development in all areas • This is particularly important for AQ modeling since
emissions occur mostly from highways, residential, and urban areas
21
Office of Research and DevelopmentAtmospheric Modeling & Analysis Division, National Exposure Research Laboratory
Next steps
• Add anthropogenic heating based on population and housing unit density• Add NLCD canopy fraction data for accurate accounting of
tree cover in all areas including urban.• Comprehensive evaluation of meteorology and AQ at all
scales
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