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WRAP RMC Phase II Wind Blown Dust Project ENVIRON International Corporation and University of California, Riverside 15 November 2005 Tempe, AZ
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Outline Phase I Project Summary Phase II Project Overview Recent Revisions & Enhancements for Base02a Modeling Results Model Performance Evaluation Next Steps
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Phase I Project Summary Objectives – Develop general methodology based on ‘MacDougall Method’ – Develop 1996 gridded PM inventory of WB Dust for the Western States Estimation Methodology – Categorize vacant land & soil types (disturbance, vegetative cover, soil texture) – Identify wind tunnel emission factors – Assign threshold wind velocities, wind & precipitation events, reservoir characteristics – Apply emission factors to vacant land as a function of wind speed & soil texture
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Data Sources – Land Use/Land Cover (LULC) BELD3, NALCC, NLCD – Soil Characteristics STATSGO; Soil Landscape of Canada; Intl. Soil Reference and Information Centre – Meteorological Data 1996 36-km MM5 – Agricultural Data BELD3; RUSLE2; CTIC
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Phase I Project Summary Limitations – Threshold surface friction velocities – Emission factors – Vacant land stability – Dust reservoirs – Rain events – Vegetation density
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Phase II Project Overview Objectives – Develop improved general methodology based on Phase I recommendations and recent literature review – Develop 2002 gridded PM inventory of WB Dust for the Inter-RPO regional modeling domain – Development of surface friction velocities and threshold friction velocities – Develop improved emission flux relationships – Improved characterization of disturbed lands – Characterize vacant lands using more up-to-date databases – Conduct model performance evaluation
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General Formulation Dust = f(LULC,z 0,u *,u *th,SC) u * = f(u,z 0 ) u *th = f(z 0 ) z 0 = f(LULC)
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Recent Literature and Models Draxler, et al., 2001 – Regional model application – Dust emissions a function of u *, u *th, z 0 – z 0 correlated with soil properties of Persian Gulf region – Assumed all soils disturbed Zender, et al., 2003 – Global model application – Dust emissions a function of u *, u *th, z 0 – Global z 0 = 0.01 cm – Uniform soil texture Shao, 2001 – Dust emissions a function of u *, u *th, z 0 – Emphasis on particle size distribution and micro forces
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Revised Methodology Threshold velocities Emission factors LULC characteristics & Soil characteristics Reservoir characteristics Agricultural adjustments
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Threshold Friction Velocities u *th determined from relations developed by Marticorena, et al, (1997)
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Emission Rates Determined from results of Alfaro and Gomes (2001) Dependent on soil type
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Dust Category3467 Land useAg.GrassShrubsBarren Surface roughness (cm)0.0310.10.050.002 Threshold friction Velocity (mile/h)8.3313.819.626.81 Threshold wind velocity at 38m height (mile/h)29.5044.2532.7528.50 Characteristics of Dust Categories
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Soil Characteristics Soil Disturbance (Sensitivity Simulations) – Disturbed soils have a greater potential for erosion – Results in reduced threshold surface friction velocities – Soils are assumed to be undisturbed – Assumed percentage of disturbance by land use type – Threshold velocities reduced from ~20% – 90%
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Reservoir Characteristics Amount and condition of soils impact dust emissions Climatological effects (rain, snow, etc.) Sandy soils dry fastest, loams medium range, clays dry slowest. Evapotranspiration rates ~ twice as high in summer than winter; ~ 1.4 times higher than spring/fall
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Agricultural Adjustments Non-climatic factors significantly decrease soil loss from agricultural lands Similar approach to CARB, 1997 (as in Phase I) Five “adjustment” factors simulate these effects: – Bare soil within fields – Bare borders surrounding fields – Long-term irrigation – Crop canopy cover – Post-harvest vegetative cover (residue)
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Data Sources Land Use/Land Cover – National Land Cover Database (NLCD) – Biogenic Emissions Landcover Database (BELD3) Soils – State Soil Geographic Database (STATSGO) – Soil Landscape of Canada (SLC) – International Soil Reference and Information Centre Meteorology – 2002 36-km Gridded MM5
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Recent Revisions for Base02a Inventory Updated LULC database Dust Transport Fractions Dust Fine Fraction (PM10/PM2.5)
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Updated LULC Database (2000)
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LULC Summary/Comparison
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Fine Fraction of Dust Original methodology used 0.78/0.22 (PMC/PMF) Revised methodology uses 0.90/0.10
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Latest Transport Fractions (Tom Pace, EPA, 6/2005) Effects of near-source dust removal & deposition Varies by LULC; Applied at grid-cell level (12- km) LULC Category Pre02dBase02a Urban0.300.00 Agricultural0.850.75 Grasslands0.700.75 Shrublands0.600.75 Forest0.300.00 Barren/Water0.971.00
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Model Results WRAP 36-km Modeling Domain
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Model Results WRAP 12-km Modeling Domain
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WRAP 12-km Modeling Results
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2002 Monthly WB PM10 Dust Emissions WRAP States
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WRAP Dust Comparison 12-km Results
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WRAP Dust Comparison 36-km Results
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WRAP Dust Comparison
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Model Results 2002 Annual WB Dust PM10 - 36-km
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36km Model Results
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Model Results 2002 Annual WB Dust PM10 - 12-km
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12km Model Results
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Model Results 2002 Annual – 12-km
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Model Results County-level -- 12-km
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Model Performance Evaluation Evaluate model results for reasonableness and accuracy Compare predicted WB dust emissions near IMPROVE monitors with measured IMPROVE dust extinction (B dust ) – Identify occurrences of: 1) Zero WB dust and near-zero B dust 2) Enhanced WB dust and near-zero B dust 3) No WB dust and elevated B dust 4) Enhanced WB dust and elevated B dust Enhancements to CMAQ to track WB and other dust Evaluate model CMAQ model performance with and with out WB dust emissions
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Saguaro West, AZ, Coarse Mass
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Saguaro West, AZ, Soil
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Salt Creek, NM, Coarse Mass
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Salt Creek, NM, Soil
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Next (Final) Steps Update/Complete Model performance Evaluation – Evaluate CMAQ model performance with & without WBD Emissions Update Project Final Report
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