1. Simulation of the indirect radiative forcing of climate due to aerosols by the two-way coupled WRF-CMAQ model over the continental United States: Preliminary results Shaocai Yu, Rohit Mathur, Jonathan Pleim, David Wong, Annmarie Carlton, Shawn Roselle, and S.T. Rao Atmospheric Modeling and Analysis Division, National Exposure Research Lab, U.S. EPA, RTP, NC 27711 Yang Shao NRC/Environmental Science Division, NERL, U.S. EPA, RTP, NC 27711

6. Meteorological Model WRF modeling System:  x=12 km 34 layers Land-Surface: PX LSM PBL: ACM2 Cloud Physics: Lin Cumulus: Kain-Fritsch Shortwave: RRTMg, or CAM Longwave: RRTMg, or CAM Coupler Chemical Transport Model CMAQ Modeling System: Photochemistry: CB05 59 organic and inorganic species, 156 chemical reactions Aerosol module: AE5 3 lognormal modes, organic and inorganic Emission: SMOKE In-line emission for biogenic species AQPREP Prepares virtual CMAQ compatible input met. files CMAQ-mixactivate: cloud drop number conc. Direct forcing: Aerosol size, composition, conc. Two-way coupled WRF-CMAQ modeling System (Interaction and feedback)

7. Aerosols: number, size, chemical composition CCN activation  Cloud droplet number Cloud microphysics (Lin et al.,): cloud vapor and water, rain, ice, snow, graupel Cloud effective radius (r e ), COD The 1 st and 2 nd IAF Coupled WRF-CMAQ aerosol simulation Aerosol activation scheme ( Abdul-Razzak and Ghan, 2000, 2002 ) Updraft velocity, liquid water content (WRF) Radiative transfer model: CAM: r e (4-20)  m; RRTMg: r e ( 2-60)  m Met fields (WRF) Sulfate, BC, dust Ice number Conc., IN Cloud microphysics (Lin et al.,): cloud vapor and water, rain, ice, snow, graupel Ice effective radius (r ie ), IOD Glaciation IAF

10.  Results (preliminary 8/4-8/31/2006) Meteorology at CASTNet: Temp.  Mean: RRTMg was slightly hotter than CAM and both are hotter than Obs Acadia NP, Maine Obs21.4±5.6 CAM22.3±5.5 RRTMg22.6±5.4 Daytime overestimate

11.  Results (preliminary) : Meteorology: Radiation  Mean: Acadia NP, Maine Obs211±282 CAM269±330 RRTMg278±334 RRTMg has slightly higher radiation than CAM and both are higher than Obs Missing observed cloud cover caused overestimation during the daytime

12.  Results (preliminary): Evaluation for PM 2.5 at AIRNOW sites  Both underpredicted obs PM 2.5 by -27% Obs13.9±7.9 CAM10.2±6.7 RRTMg9.5±5.9

13.  Results (preliminary): at IMPROVE sites  Model underpredicted obs PM 2.5 by -32% because of underestimation of SO 4 2- (-26%) and OC (-25%) NMB (%) meanObsCAM RRTMgCAMRRTMg SO 4 2- 3.072.272.36-26-23 NO 3 - 0.220.210.16-7-29 PM 2.5 8.245.605.51-32-33 OC1.351.021.00-25-26 EC0.330.250.24-24-27

14.  Results: (8/4/2006, 3:00 PM), ground-level PM 2.5 and CCN1 (S=0.02%), CCN2 (S=0.05%), CCN3 (S=0.1%)  CAM:  RRTMg

15.  Results: (8/4/2006, 3:00 PM), Layer 13 (~1 km) PM 2.5, Cloud drop #, Cloud LWC, Droplet effective radius  CAM:  RRTMg w4wrfout_d01_2006-08-04_00.ncf Effective radius (  m)

16.  Results: Satellite visible imagery of cloud and modeled shortwave cloud forcing on 8/4/2006 3:00 PM RRTMg CAM Shortwave cloud forcing

17.  Results: Monthly means of modeled SWCF to compare with CERES obs (preliminary results)  Modeled SWCF close to Obs over GA area  Model underestimated the Obs SWCF over central and NE areas ( underestimated cloud ) 12 km (CAM) ~250 km (2.5 degree) 12 km (RRTMg)

18.  Results: Monthly means of modeled SWCF: Interpolate to 250 km resolution for model 250 km (CAM) ~250 km (2.5 degree) 250 km (RRTMg)

19.  Results: Comparison of Monthly means SWCF: Obs-48.1±17.6 CAM-31.9±13.3 RRTMg-19.8±9.0  Both underpredicted obs SWCF by more than -33%, especially for high SWCF.  Mean: (watts m -2 )

20. Contacts: Brian K. Eder email: eder@hpcc.epa.gov www.arl.noaa.gov/ www.epa.gov/asmdnerl

21. Tracks of ship Tracks of P-3 flights

22. NO 3 - NH 4 + SO 4 = Na + Cl - H 2 O POA SOAc SOA a SOA b EC Other HNO 3 NH 3 H2OH2O NO 3 - NH 4 + SO 4 2- Na + Cl - Soil Other Coarse modeAccumulation mode H 2 SO 4 HCl  CMAQ: Aerosol chemical composition for each mode Aitken mode NO 3 - NH 4 + SO 4 = Na + Cl - H 2 O POA EC Other SVOCs HNO 3 NH 3 H2OH2O HCl Monoterpenes Aromatics ISORROPIA model

23.  CMAQ resolves aerosol size-distribution by 3 log-normal modes Aitken (0.03-0.1 µm), Accumulation(0.1-2.5 µm): Coarse (>2.5 µm): CoarseAccumulation Aitken Fine particle (PM 2.5 ) Low volatility vapors Emissions Coagulation Chain aggregates Coagulation Condensation growth of nuclei Homogeneous nucleation Coagulation Chemical reactions Mass transfer Sedimentation Wind blown dust Emissions Sea Spray Rainout washout Evaporation (cloud processes)

24.  Mean: RRTMg (r e : 4-20  m) has slightly lower radiation than RRTMG ( r e : 2-60  m ) ) Obs236±299 CAM (4-20  m) 297±346 RRTMg (2-60  m) 304±349 RRTMg (4-20  m) 303±349  Results (8/4-8/12) : Radiation comparison for RRTMg (2-60  m) and RRTMg (4-20  m)

25.  Results (8/4-8/12) : SWCF Comparison for RRTMg (2-60  m) and RRTMg (4-20  m) RRTMg (4-20  m) has slightly higher SWCF than RRTMG (2-60  m) (1) CAM (r e :4-20  m) (3) RRTMg ( r e : 2-60  m) (3) RRTMg ( r e : 4-20  m) Optical properties of cloud calculated by: CAM: Slingo (1989) for r e :4-20  m RRTMg: Hu and Stanmes (1993) for r e :2-60  m

27. CAM  Results: Satellite visible imagery of cloud and modeled shortwave cloud forcing on 8/6/2006 3:00 PM RRTMg Shortwave cloud forcing