William G' Benjey

1
Relative Effects of Observationally- Nudged
Modeled Meteorology and Down-Scaled Global
Climate Model
Meteorology
on Biogenic Emissions

• William G. Benjey
• Physical Scientist
• NOAA Air Resources Laboratory
• Atmospheric Sciences Modeling Division
• Research Triangle Park, NC
• Fifth Annual CMAS Conference, Chapel Hill, NC,
  October 18, 2006

In partnership with the U.S. EPA National
Exposure Research Laboratory
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Outline

• Climate Impact on Regional Air Quality (CIRAQ)
  program
• Observationally nudged vs. regional climate model
  (RCM) meteorology
• Relative effects of nudged and RCM meteorology on
  biogenic emissions, with the focus on three-year
  modeled period and summer seasons
• Biogenic emissions relative to modeled
  meteorology patterns
• Conclusions
• Next steps

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CIRAQ Program

• Objective Assess potential climate change
  impacts on O3 and PM using EPAs Community
  Multiscale Air Quality (CMAQ) model linked with
  global-scale climate and chemical transport
  models.
• Supports the U.S. Climate Change Science Program
  (CCSP) research goals and synthesis products

4
Key CIRAQ Questions

• How will future climate change and variability
  affect regional air quality over the United
  States?
• What is the principle driver for future air
  quality (climate change and variability vs.
  technology-driven emissions)?
• How will meteorologically-dependent mobile source
  and biogenic emissions respond to future climate
  conditions?
• What are the strengths and weaknesses of using
  the down-scaled climate models for regional air
  quality assessments? What climate modeling
  improvements are needed?

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CIRAQ Emissions

• Phase 1 (by 2007)
• Five year base case (2000)
• Five year future case (2050)
• Current anthropogenic emissions
• Meteorologically dependent biogenic and mobile
  source emissions
• Phase 2 (by 2010)
• Add alternative future emission scenarios.

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Regional Climate Model and Observationally Nudged
Meteorology

• Most retrospective CMAQ simulations use
  observationally-nudged meteorological input
• CIRAQ/CMAQ uses RCM inputs without observational
  nudging
• Question Does lack of nudging create biases in
  current period emission simulations that might
  obscure a climate change signal due to noise
  in the meteorology modeling of the future?

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Effects of Nudged and RCM Meteorology on Biogenic
Emissions

• Nudged MM5 meteorology for 2001-2003 and 5
  current (base) years of RCM meteorology prepared
  for a U.S. modeling domain with 36km x 36km cell
  resolution
• Hourly biogenic emission data for Isoprene and
  Nitric Oxide (NO) generated using the BEIS 3.13
  model in the SMOKE emission model with the
  meteorology data
• Biogenic emission data area normalized over
  geographic regions to aid analysis of spatial and
  temporal patterns
• Regions include model domain, Eastern and Western
  U.S. and Canada, and five eastern ozone regions
• Ozone regions identified using principal
  component analysis (Lehman et al., 2004)

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Western and Eastern Regions
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Ozone Regions
After Lehman et al., 2004
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Effects on Biogenic Emissions (3)


RCM 5 recent model years Nudged 2001,
2002, 2003
Area Normalized Emission Statistics by Region for
RCM and Nudged Meteorology
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Effects on Biogenic Emissions (4)
RCM
Nudged
(5 recent years)
(2001-2003)
Mean Hourly Isoprene Emissions
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Effects on Biogenic Emissions (5)
Observations on Biogenic Emissions

• With the exception of Region 1, mean hourly
  biogenic Isoprene and NO emissions based on
  nudged meteorology greater than when based on RCM
  meteorology
• Percent difference larger for Isoprene than for
  NO
• Because Isoprene emissions depend on insolation
  as well as temperature, they vary more than NO,
  which depends on temperature and precipitation

13
Effects on Biogenic Emissions (6)


RCM 5 recent model years Nudged2001, 2002,
2003
Summer Season Area Normalized Emission Statistics
by Region for RCM and Nudged Meteorology
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Effects on Biogenic Emissions (7)
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Effects on Biogenic Emissions (8)
Observations on Summer Emissions

• Summer mean hourly biogenic emissions more
  variable than annual mean hourly emissions
  (variance)
• Isoprene emissions based on nudged meteorology
  greater than RCM-based Isoprene emissions in all
  regions
• Mean hourly NO emissions based on nudged
  meteorology greater than RCM-based emissions
  except Region 1
• RCM and nudged meteorology biases in general
  produce consistent emission biases. However,
  meteorological drivers (insolation, temperature,
  precipitation) not spatially consistent
• Region 1 (Northeast) produces greatest
  RCM-to-nudged emission difference (33.7), but
  NO emission differences opposite sign

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Meteorological Patterns

• Principal component analysis reveals differences
  in RCM meteorology and NARR meteorology data sets
  based on observations. NARR similar to
  observationally nudged meteorology
• Surface pressure, precipitation, 2 m temperature
  data extracted and sea level pressure calculated
  (1800 Z rather than all hours)
• Bermuda High behavior not replicated by RCM
  meteorology
• Summer RCM meteorology has relatively cool, dry
  high pressure conditions over the north and
  northeastern US and southern Canada during the
  summer

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Summer Meteorological Patterns

• Summer RCM temperatures 2 to 10 oK cooler over
  northern domain east of the Rocky Mountains
• RCM underestimates precipitation for the eastern
  US

Summer RCM-NARR temperature differences (Gilliam
and Cooter, submitted)
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Summer Biogenic Emission Patterns

• Nudged Meteorology to RCM Meteorology-based
  Isoprene and NO emission differences greater in
  Eastern Region than Western Region consistent
  with a cooler, dryer east in the meteorology
  analysis
• Region 1 RCM-NARR summer temperature differences
  small overall - 1o K warmer over water near the
  coast and neutral to 1oK cooler inland
• RCM-based Region 1 NO summer emissions very close
  to Nudged-based NO summer emissions consistent
  with small temperature difference and no
  insolation dependence. RCM-based emissions
  slightly greater (-4.1 percent)

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Summer Biogenic Emission Patterns (2)
Isoprene Emissions (top Nudged, bottom RCM)
NO Emissions (top Nudged, bottom RCM)
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Conclusions

• RCM-based biogenic emissions generally less than
  Nudged Meteorology-based biogenic emissions,
  especially for Isoprene and especially in the
  Northeast
• Consistent with summer RCM to NARR meteorology
  temperature differences
• Percent difference between RCM and Nudged
  meteorology-based biogenic emissions varies by
  region and by compound (Isoprene and NO).
  Reflects spatial differences in meteorological
  patterns
• Initial indication that RCM-based Isoprene
  emissions could contribute to any tendency to
  under predict current period simulations of ozone
  concentrations in the Northeastern United States.

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Next Steps

• Complete detailed evaluation of the RCM to Nudged
  meteorology biogenic emissions for other seasons
  and other geographic regions
• Look for sub-regional hot spots in the gridded
  emission data
• Examine RCM to Nudged emission differences with
  respect to differences in CMAQ modeled ozone
  concentrations.
• Apply the results to future year (2050) biogenic
  emissions based on RCM meteorology
• Apply results to future year CMAQ model runs and
  evaluate output concentrations in the context of
  meteorology and emission patterns

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Acknowledgements

• Aid and comments from
• Ellen Cooter
• Rob Gilliam
• Steve Howard
• Rohit Mathur
• Donna Schwede
• Jenise Swall

23
Disclaimer

• The research presented here was performed
  under the Memorandum of Understanding between the
  U.S. Environmental Protection Agency (EPA) and
  the U.S. Department of Commerces National
  Oceanic and Atmospheric Administration (NOAA) and
  under agreement number DW13921548. This work
  constitutes a contribution to the NOAA Air
  Quality Program. Although it has been reviewed
  by EPA and NOAA and approved for publication, it
  does not necessarily reflect their policies or
  views.