1 / 32

with support from EPRI, NASA Dalhousie University, May 19, 2006

NATURAL AND TRANSBOUNDARY POLLUTION INFLUENCES ON REGIONAL VISIBILITY STATISTICS IN THE UNITED STATES. Rokjin Park. with support from EPRI, NASA Dalhousie University, May 19, 2006. NATIONAL PARKS AND OTHER NATURAL AREAS IN THE U.S. SUFFER SIGNIFICANT VISIBILITY DEGRADATION FROM

charlesgates
Download Presentation

with support from EPRI, NASA Dalhousie University, May 19, 2006

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NATURAL AND TRANSBOUNDARY POLLUTION INFLUENCES ON REGIONAL VISIBILITY STATISTICS IN THE UNITED STATES Rokjin Park with support from EPRI, NASA Dalhousie University, May 19, 2006

  2. NATIONAL PARKS AND OTHER NATURAL AREAS IN THE U.S. SUFFER SIGNIFICANT VISIBILITY DEGRADATION FROM ANTHROPOGENIC AEROSOLS. 7.6 µgm-3 12.0 µgm-3 Glacier National Park 21.7 µgm-3 65.3 µgm-3

  3. ATMOSPHERIC PARTICULATE MATTER (AEROSOLS) Aerosol: dispersed condensed matter suspended in a gas Size range: 0.001 mm (molecular cluster) to 100 mm (small raindrop) Lifetime ≈ 4 – 6 days Soil dust Sea salt SO2, NOx, NH3, VOCs • Most important components of the atmospheric aerosol: • Sulfate- nitrate-ammonium • Organic carbon (OC), elemental carbon (EC) • Soil dust • Sea salt

  4. VISIBILITY METRIC • VISUAL RANGE (km) - THE GREATEST DISTANCE AT WHICH AN OBSERVER • CAN SEE A BLACK OBJECT VIEWED AGAINST BACKGROUND HORIZON • - A quantitative measurement is subject to other conditions (Sun angle, • light condition) than aerosol concentrations. • EXTINCTION (bext, Mm-1) - THE AMOUNT OF LIGHT LOST AS IT TRAVELS OVER • A MILLION METERS • - Most useful for relating visibility directly to aerosol concentrations. • - bext = 3f(RH)[(NH4)2SO4 + NH4NO3] + 4[OMC] + 10[EC] + [SOIL] + 0.6[CM] + 10 • DECIVIEWS (dv) – THE LOGARITHM OF THE EXTINCTION • - dv = 10ln(bext/10) • - A change in one dv is perceived to be the same under different conditions • (clear and cloudy days). [Pitchford and Malm, 1994]

  5. Anthropogenic emissions (illustrative) U.S. EPA REGIONAL HAZE RULE • Federal class I areas (including national parks, other wilderness areas) to return to “natural visibility” conditions by 2064 • State Implementation Plans to be submitted by 2007 for linear improvement in visibility over the 2004-2018 period visibility (deciviews) from EPA [2001] Because visibility is a logarithmic (sluggish) function of PM concentration, The 2004-2018 phase I implementation requires ~50% reduction in emissions, highly sensitive to specification of 2064 endpoint

  6. OBJECTIVE #1 PM mass concentration (mg m-3) Extinction coefficient (Mm-1) U.S. EPA HAS PROPOSED“DEFAULT ESTIMATED NATURAL PM CONCENTRATIONS” FOR APPLICATION OF THE REGIONAL HAZE RULE These defaults are based on measurements at clean remote sites [NAPAP report, 1990]. A better quantification of natural aerosol concentrations is crucial.

  7. OBJECTIVE #2 Clear day April 16, 2001: Asian dust! TRANSBOUNDARY TRANSPORT COMPLICATES THE DEFINITION OF “NATURAL VISIBILITY” Glen Canyon, AZ Dust storms provide visible evidence of intercontinental transport of aerosols and anthropogenic pollution is transported together with the dust satellite data satellite data [Heald et al., 2005]

  8. GEOS-Chem GLOBAL 3-D MODELOF ATMOSPHERIC TRANSPORT AND CHEMISTRY http://www-as.harvard.edu/chemistry/trop/geos • Developed by Harvard Atmospheric Chemistry Modeling Group, used by 17 research groups in N. America and Europe; ~100 publications. • driven by GEOS assimilated meteorological observations from NASA Global Modeling and Assimilation Office (GMAO); native resolution 1ox1o • applied to simulations of ozone, aerosols (PM), CO2, methane, mercury, hydrogen,… • Horizontal resolution 1ox1o to 4ox5o (user-selected), 48 levels in vertical • Previous global evaluation of aerosol simulations in the United States, Europe, and East Asia by Park et al. [2003, 2004a, 2004b]; global evaluation by Martin et al. [2004]. • Conduct 1ox1o nested model simulations over North America with boundary condition from 4ox5o global model simulation.

  9. NH4+ H2O SO42- NO3- SULFATE-NITRATE-AMMONIUM AEROSOL Aerosol thermodynamic calculations using RPMARES or ISORROPIA Solid f(T, RH, C) Aqueous phase pH = 4.5 H2SO4 SO42- (NH4)2SO4 NH4NO3 HNO3 H2O2 (aq), O3 (aq) Lightning OH OH (N2O5) NOx NH3 SO2 OH, NO3 DMS Ocean Volcanoes Fossil fuel Domesticated Fertilizers Fossil Fuel Biomass Animals burning

  10. Gi,j Pi,j Equilibrium (Komi,j)  also f(POA) Ai,j ORGANIC CARBON AEROSOL Condense on pre-existing aerosol SECONDARY ORGANIC AEROSOL (SOA) SIMULATION [Chung and Seinfeld, 2002] VOCi + OXIDANTj ai,jP1i,j+ ai,jP2i,j Parameters (a’s K’s) from smog chamber studies Reactive Organic Gases Oxidation by OH, O3, NO3 Biogenic VOCs (Monoterpenes) Direct Emission Isoprene as a SOA source? [Claeys et al., 2004; Matsunaga et al., 2005; Lim et al., 2005; Kroll et al., 2005; Henze and Seinfeld., 2006; van Donkelaar et al., in review] Aromatics Fossil Fuel Biomass Vegetation combustion burning

  11. BLACK CARBON IN THE ATMOSPHERE BC is operationally defined as the light-absorbing fraction of carbonaceous aerosols. CHEMICAL AGING WET DEPOSITION PRIMARY EMISSION coating by sulfate or organics oxidation Hydrophobic Hydrophilic How long ()? How much? Most global models assume  = 1 day for chemical conversion of hydrophobic to hydrophilic BC.

  12. 2001 GEOS-Chem 1ox1o NESTED SIMULATIONS • Uses the coupled oxidant-aerosol version of GEOS-CHEM (version 7.02) with 1ox1o horizontal resolution over North America (140-40oW, 10-60oN) and 4ox5o horizontal resolution for the rest of the world. • Includes weekday and weekend NEI99 anthropogenic emissions for NOx, CO, NMHC, and SO2 in the United States, EC and OC primary emissions from Bond et al. [2004] and Park et al. [JGR 2003], respectively. • Include sulfur emissions in Canada and Mexico from EMEP and BRAVO emission estimates, respectively. • Include a global ship SO2 emission [Corbett et al., 1999; Alexander et al., 2005]. • Includes a climatological biomass burning emission inventory with emission factors from Andreae and Merlet [2001]. • Includes a mechanistic simulation of secondary organic aerosols [Chung and Seinfeld, JGR 2002] coupled to oxidant chemistry • Applies HNO3 and NH3 dry deposition to the mixed layer column. • Four simulations are conducted for 16 months starting from September 1, 2000: • baseline (emissions as described above) • natural (zero anthropogenic emissions worldwide) • background (zero anthropogenic emissions in the U.S.) • transpacific (zero anthropogenic emissions in North America)

  13. ANNUAL MEAN SULFATE (2001): GEOS-Chem (1ox1o) vs. IMPROVE (135 sites) Highest concentrations in industrial Midwest (coal-fired power plants)

  14. SULFATE AT IMPROVE, CASTNET, NADP (deposition) SITES:model (1ox1o) vs. observed for different seasons High correlation in sulfate concentrations for different seasons (R2 = 0.83 - 0.92) Low bias in summer and high bias in other seasons (Slope = 0.84 - 1.32)

  15. ANNUAL MEAN AMMONIUM AND NITRATE (2001): GEOS-Chem vs. CASTNET (79 sites) (no ammonium data at IMPROVE sites) Highest concentrations in upper Midwest NO3- NH4+ The spatial distribution of ammonium and nitrate reflect the dominant ammonium nitrate formation in North America.

  16. Ammonium Nitrate Nitrate AMMONIUM AND NITRATE AT CASTNET AND IMPROVE SITES: model (1ox1o) vs. observed for different seasons High correlation for different seasons (R2 = 0.82-0.85) High bias for NH4+ in fall: error in seasonal variation of livestock emissions High bias for NO3-, esp. in summer/fall, results from bias on [SO42-]-2[NH4+]

  17. ANNUAL MEAN EC AND OC (2001):GEOS-Chem (1ox1o) vs. IMPROVE (135 sites) GEOS-Chem IMPROVE [µg m-3] • High OC in southeast U.S.: vegetation • High EC/OC in west: fires

  18. EC OC EC AND OC AT IMPROVE SITES: model vs. observed for different seasons Low bias for EC indicates that Bond et al. [2004] EC emission could be low in the U.S. No significant bias in OC with Park et al. [2003] emission but large scatter mostly from SOA simulation dependent on preexisting primary organic aerosols [Chung and Seinfeld, 2002]

  19. VISIBILITY DEGRADATION STATISTICS IN THE U.S. (2001): IMPROVE vs. GEOS-CHEM (1ox1o) R2 = 0.88 R2 = 0.63 Visibility extinction (deciviews: dv = 10ln(bext/10) ) from sulfate, nitrate, EC, and OMC.

  20. Too much monoterpene emission in northwest Ammonium nitrate is too low in Southern California Too much wet scavenging in southeast CUMULATIVE DISTRIBUTION OF VISIBIILTY DEGRADATION IN THE U.S. (2001): IMPROVE (black) vs. GEOS-CHEM (red) Deciviews Model reproduces daily visibility degradation successfully at 53 out of 87 sites in the west and 24 out of 44 sites in the east. Mexican sulfur emission in BRAVO inventory is lower by 30% than Mexican NEI or global emission inventory.

  21. GEOS-CHEM SIMULATION OF TRACE-P OBSERVATIONS Scavenging from Asian outflow is 80-90% efficient for sulfate and BC, ~100% for nitrate TRACE-P (Mar-Apr, 2001) flight tracks for DC-8, P3-B aircraft P3B DATA over NW Pacific (30 – 45oN, 120 – 140oE) Black carbon (BC) Model underestimates BC observations by factor of 2; insufficient emissions [Bond et al., 2004] or excessive scavenging?

  22. EXPORT EFFICIENCY BC emissions over East Asia are highly uncertain [Carmichael et al, 2003]. [Koike et al., 2003; Parrish et al, 2004] X = combustion-derived species RX = emission ratio (X/CO) Δ = enhancements relative to background NORMALIZED EXPORT EFFICIENCY INDEPENDENT OF EMISSION RATIO, R We use the TRACE-P P-3B data north of 30oN for which China provided a common source region.

  23. OBSERVED EXPORT EFFICIENCYBC vs SOX(≡SO2(g)+SO42-) and HNO3T(≡HNO3(g)+NO3-) Export efficiency Normalized export efficiency BC AEROSOLS ARE SIGNIFICANTLY SOLUBLE BUT NOT AS MUCH AS SULFATE OR NITRATE. [Park et al., 2005]

  24. BC NORMALIZED EXPORT EFFICIENCY IN ASIAN OUTFLOW (GEOS-Chem vs TRACE-P ) Simulation with  = 1±1 days for BC scavenging provides the best fit to the TRACE-P observations. [Park et al., 2005]

  25. IMPLICATION FOR CLIMATE BC BURDEN & ARCTIC DEPOSITION FLUX BC lifetime is 5.8 ± 1.8 days, 50% longer than that of sulfate, global burden is 0.11 ± 0.03 Tg using Bond et al. [2004] inventory, and resulting decrease in Arctic snow albedo = 3.2 ± 2.5% with  = 1 ± 1 days from the TRACE-P constraints [Park et al., 2005]

  26. CONTIGUOUS U.S. MAP (1ox1o):background simulations with shutting off U.S anthropogenic emissions

  27. SIMULATED NATURAL AND BACKGROUND ANNUAL MEAN AEROSOL CONCENTRATIONS IN THE UNITED STATES

  28. SIMULATED NATURAL AND BACKGROUND ANNUAL MEAN AEROSOL CONCENTRATIONS (CONT.)

  29. AEROSOL CONCENTRATIONS IN THE U.S.:contributions from natural sources and transboundary pollution Annual regional means averaged at IMPROVE sites from GEOS-Chem standard and sensitivity simulations • Transboundary pollution influences from Canada & Mexico are higher than those in Park et al. [2003, 2004], resulting in factor of 4 higher background concentration of ammonium sulfate than EPA default value.

  30. END POINT VISIBILITY DEGRADATION FOR WORST 20% DAYS IN THE UNITED STATES • The EPA default endpoint visibility shows a simple separation between the western and the eastern United States for which we find little basis. • Our natural visibility endpoint has a considerable spatial variation and in general lower than the EPA default in the east. • Background endpoint visibility is higher than natural visibility and is more spatially variable due to transboundary pollution influences.

  31. IMPLICATIONS FOR EMISSION REDUCTIONS IN PHASE 1 (2004-2018) IMPLEMENTATION OF REGIONAL HAZE RULE Illustrative calculation for NW IMPROVE sites based on 20% worst visibility days statistics, assuming linear relationship between emissions and PM concentrations, and assuming constant anthropogenic sources from foreign countries between now and 2064 Desired trend in visibility Phase 1 VISIBILITY DEGRADATION ON 20% WORST VISIBILITY DAYS AT NORTHWESTERN IMPROVE SITES. 53% Required % decrease of U.S. anthropogenic emissions 28%

  32. PROJECTED SOx EMISSIONS IN ASIA • One projection suggests that • emissions of SOx will more than • double in China between • 1995-2020 • [Streets & Waldhoff, 2000] courtesy: David Streets Increasing SOx emissions from Asia will degrade North American air quality and present a further barrier to attainment of domestic air quality regulations in the United States (eg. EPA Haze Rule)

More Related