title: CMAQ model performance enhanced when in-cloud secondary organic aerosol is included: comparisons of organic carbon predictions with measurements.
abstract: Mounting evidence suggests that low-volatility (particle-phase) organic compounds form in the atmosphere through aqueous phase reactions in clouds and aerosols. Although some models have begun including secondary organic aerosol (SOA) formation through cloud processing, validation studies that compare predictions and measurements are needed. In this work, agreement between modeled organic carbon (OC) and aircraft measurements of water soluble OC improved for all 5 of the compared ICARTT NOAA-P3 flights during August when an in-cloud SOA (SOAcld) formation mechanism was added to CMAQ (a regional-scale atmospheric model). The improvement was most dramatic for the August 14th flight, a flight designed specifically to investigate clouds. During this flight the normalized mean bias for layer-averaged OC was reduced from -64 to -15% and correlation (r) improved from 0.5 to 0.6. Underpredictions of OC aloft by atmospheric models may be explained, in part, by this formation mechanism (SOAcld). OC formation aloft contributes to long-range pollution transport and has implications to radiative forcing, regional air quality and climate.
authors.affiliation: Air Resources Laboratory, Atmospheric Sciences Modeling Division, National Oceanic and Atmospheric Administration, 109 TW Alexander Drive, Durham, North Carolina 27711, USA. carlton.annmarie@epa.gov
authors.forename: Annmarie G
authors.initials: AG
authors.lastname: Carlton
authors.forename: Barbara I
authors.initials: BI
authors.lastname: Turpin
authors.forename: Katye E
authors.initials: KE
authors.lastname: Altieri
authors.forename: Sybil P
authors.initials: SP
authors.lastname: Seitzinger
authors.forename: Rohit
authors.initials: R
authors.lastname: Mathur
authors.forename: Shawn J
authors.initials: SJ
authors.lastname: Roselle
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Weber
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000401:Aircraft; D001272:Atmosphere / Q000737:chemistry; D002244:Carbon / Q000032:analysis*; D007391:International Cooperation; D008956:Models, Chemical; D009930:Organic Chemicals / Q000032:analysis*; D012995:Solubility; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D009930:Organic Chemicals; D014867:Water; D002244:Carbon