Introducing CMAQ: Overview and Preliminary Results

1. Introducing CMAQ:Overview and Preliminary Results Robin Dennis Atmospheric Sciences Modeling Division NOAA/EPA Chesapeake Bay Air Modeling Meeting October 11, 2005 Chesapeake Bay Program Annapolis, MD

2. Overview of Presentation • Brief Overview of Changes to Modeling and Modeling System: CMAQ = Community Multiscale Air Quality model • Compare Performance of CMAQ and Extended RADM • Insights and Results of the New Approach to Climatology and Recommended Update of the Atmospheric Deposition Linkage to the Watershed Model • Preliminary 2010 CAIR Scenario Results and Implications • Discussion of Future Work

3. Overview of Changes to Model and Modeling System • CMAQ Model (Changes) • New Climatology Set for Long-Term Averages • Three years that represent a wet, a dry and a normal precipitation year are used. • Three years can represent the average transport from source regions to the Bay watershed. • New Grid • Continental 36 km • New Base Year • Moved from 1990 to 2001.

4. Overview of Changes to Model • CMAQ Model • Wet deposition includes resolved cloud systems • especially relevant for cold season • Updated dry deposition algorithms for NH3, HNO3, SO2 and PMfine in CMAQ (everything) • Especially affects estimates for NH3 dry deposition, increasing the values significantly • Additional species included in Ox-N deposition to be more complete and accurate (NOX emiss) • Updated total nitrate production to reflect current state of the science (still uncertainties) • Included heterogeneous pathway of HNO3 production; especially important in cold season • Updated inorganic aerosol equilibrium model to better calculate partitioning of total-ammonia and total-nitrate (ISORROPIA) • We have also spent more time studying the partitioning because of work with fine particles • More vertical resolution at surface for better ground-level concentrations for dry deposition and new subgrid-cloud mixing algorithm • Sea salt in CMAQ still coming

5. New Climatology Set for Regional Transport • New set of 3 complete years • Used to be 40 5-day cases • Now wet, dry and “normal” year • New set designed to be consistent with more recent meteorology (2001-2003) • Meteorological model parameterizations more up-to-date and tailored for use with CMAQ (parameterizations as of 2004/2005). • Climatology or Aggregation set designed for 4 seasons (even monthly), not just two seasons • better seasonal predictions to give to watershed model • can even go monthly

6. 3-Year Set Simulated with New 36-km Continental Grid • Coarse grid now at 36-km instead of 80-km and covers the continental U.S. instead of only the eastern half. • Improves the representation of the long-range flow of pollutants from the Rocky Mountain West and the mid-West • Because of the higher resolution, and • Because the boundary conditions are out over the oceans where it is relatively cleaner and the concentration levels are developed internally. • Higher resolution improves the representation of flow over and around the Appalachians and ocean influences and orographic effects on precipitation.

7. CMAQ 36-km Continental Grid

8. 3-Year Set Combines a Wet, Normal, and Dry Yearfor Mid-Atlantic Region toCreate the Average Deposition • 2001 – Dry Year • 2002 – Normal Year • 2003 – Wet Year • Use 2001-2003 Average for our climatology

9. 2001-2003 Average 2001 – Dry Year

10. 2002 – Normal Year 2003 – Wet Year

11. Compare Performance of CMAQ 3-Year with Extended RADM

12. NADP Wet Deposition CASTNet Air Concentrations

19. R2=0.8

20. CMAQ Performance • CMAQ is more complex than the Extended RADM. YET, CMAQ performance is better. • We are now more aware of many relevant dynamics because of our CMAQ work for the new PM2.5 (fine particle) standards. CMAQ is better-suited to the multi-media task. • CMAQ has biases that need to be addressed • Biases have become more visible with the use of 3 full years of meteorology to produce the average deposition. • We believe much of the air concentration biases for total nitrate stems from the over-production of HNO3 in heterogeneous pathway (cold season). • There are wet deposition biases we do not yet understand • Especially NO3 summer under-deposition

24. New Ratios and Fractions Extended RADM 1990 Red-N to Ox-N Ratio: 0.44

26. Spring Summer

28. Spring Summer

29. Recommended Approach to Linkage with Watershed Model • The high spatial and seasonal variability in the dry-to-wet ratios suggests we introduce a different approach to linkage between the air and water models. • 2001 Base • We simply provide the climatological dry Ox-N and Red-N deposition fields to the Watershed modelers. Seasonal or Monthly. • This will, for the first time, include dry deposition of ammonia and ammonium. • Scenarios • We provide the relative change in wet deposition in % per the mapping between the CMAQ cells and the watershed segments. • We provide the relative change in dry deposition in % per the mapping between the CMAQ cells and the watershed segments.

30. Old vs. New Scenario ResultsNOx SIP Call • The smaller % reduction for CMAQ Ox-N from 2001 seems quite reasonable: • The MOBILE model indicates there should be NOx • emission reductions, especially after 1997. • The CEM data for Electricity Generating Units shows • a decline in emissions from 1997 on. • Thus, 2001 Base NOx should be relatively smaller.

31. Preliminary Scenario Results2010 NOx SIP Calland 2010 CAIR Controlwith CMAQ • 2010 CAIR NOx emissions reductions, affecting Ox-N, take place only in the non-ozone season, that is, from October to April. During May to September there is only a very small reduction in NOx emissions in the airshed. • We did not pay much attention to Red-N and the dynamics in the inorganic system with the Extended RADM. • We are now much more sensitive to the nonlinearities simulated by CMAQ after our experience in analyzing and under-standing the inorganic fine particle response to emissions changes.

32. NOx SIP CAIR Control

33. NOx SIP Increase % CAIR Control Increase %

34. NOx SIP CAIR Control

35. Nonlinear Response of Red-N Deposition to Changes in Non-NH3 Emissions • Between 2010 NOx SIP case and 2010 CAIR Control • ammonia emissions did not change. • Between 2001 and the 2010 NOx SIP case the Red-N • deposition increased by 4%. • For the Bay States and Airshed states estimated • ammonia emissions increased by 4% & 5%, respectively, between 2001 and 2010.

36. PRIMARY EMISSIONS VOC CO SO2 NO OH O3 HO2 RO2 hv O3 OH H2O2 O3 Fe NO2 NO3 O3 OH N2O5 NH3 HNO3 H2SO4 H2O Heterogeneous Gas Phase Fine Particles NO3 PMfine SO4 PMfine Inorganic Fine-Particle Interactions

37. Equally Wet Deposited Base Ammonium associated With nitrate & sulfate Air Concentrations NHX HNO3 NO3- SO4= NH3 NH4+ Dry Deposition NH3~ 10 X’s faster than NH4+

38. Wet Deposition Decreases Equally Wet Deposited Air Concentrations NHX Air Concentrations Decrease HNO3 NH3 NO3- NH3 SO4= NH4+ NH4+ Base NOX & SO2 Control HNO3 NO3- SO4= Dry Deposition Increases Dry Deposition

39. NOx SIP to CAIR Decrease % NOx SIP to CAIR Decrease % Increase %

40. NOx SIP 0 % CAIR

41. Max Decrease % NOx SIP to CAIR NOx SIP to CAIR Max Increase %

42. NOx SIP to CAIR Decrease % NOx SIP to CAIR Decrease % 0 % Increase %

43. Further CAIR Analysis per Estimation of Load Reduction to Bay • Follow analysis presented in the “EPA’s Chesapeake Bay Program Air Strategy” document of October 26, 2004 • Use the same scaling factors between deposition to watershed and TN load to the Bay for REMSAD modeling as inferred from Figure 2’s histogram.

44. REMSAD ResultsCAIR Ox-N Reductions 2010 NOx SIP Base 2010 CAIR Control

45. Preliminary Scenario ResultsDirect Absolute Numbers (wet bias-corrected) CMAQ * Assumes ΔN-air-deposition of 59.7 (=369.2 - 309.5) million lbs of TN/yr translates to an N-load reduction of 10 million lbs of TN/yr (from REMSAD histogram)

46. Future Effort • Continue to shake down the CMAQ climatological simulations; check out and work on biases (sensitivity analyses). • CMAQ sensitivity analyses to better understand the nonlinearities in reduced nitrogen deposition. • Getting ready for CMAQ with sea salt (February/March 2006) • Link in coarse mode interactions • Work on better linkage of CMAQ with the Watershed model and Bay by including a 12-km Mid-Atlantic Grid. Priority?? • Reassess the futures scenarios beyond 2010, 2015 and 2020 CAIR runs. • New emissions coming for CAIR+CAMR+BART; Some work may be required to create a 2020 LOT; a 2030 future is highly uncertain.

47. Decrease 0 % Increase

48. CMAQ 36-km Continental Grid with Nested 12-km Mid-Atlantic Grid We don’t have all of the 12-km meteorology yet

50. Futures Scenarios • Characterizing bias in Base dry deposition • 2010 NOx SIP + Tier II • 2010 CAIR • 2015 CAIR+CAMR+BART + others (new) • 2020 CAIR+CAMR+BART + others (new) • 2020 LOT (possibly other than EGU’s) • 2020 Extreme EGU reduction (needed?) • 2030 (very doubtful) (could be ginned up holding EGU’s constant) • Bay State Contributions (5-6) (relative to 2020 CAIR control case – recommendation) • 12-km resolution scenarios (critical ones)