under-predictions Barron Henderson 1 , 2 , Robert Pinder 2 , Wendy - PowerPoint PPT Presentation

The role of chemistry in upper troposphere NO 2 under-predictions Barron Henderson 1 , 2 , Robert Pinder 2 , Wendy Goliff 3 , William Stockwell 4 , Askar Fahr 4 , Golam Sarwar 2 , Bill Hutzell 2 , Rohit Mathur 2 , William Vizuete 1 , Ron Cohen 5 1 Dept. of Environmental Science and Engineering UNC Chapel Hill 2 Atmospheric Modeling and Analysis Division, U.S. EPA 3 Division of Atmospheric Sciences, Desert Research Institute 4 Dept. of Chemistry, Howard University 5 Depts. of Chemistry and Earth and Planetary Sciences, University of California Berkeley October 21, 2009 Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 1/16

CMAQ compared with SCIAMACHY: worst in rural areas. CMAQ SCIAMACHY Figure 1: NO 2 columns (10 15 molec / cm 2 ) from Napelenok ACP 2008 Background Polluted Figure 2: Vertical profiles of background and polluted conditions from Singh 2007. Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 2/16

Which model processes lead to under-prediction? Potential sources of error: chemistry, photolysis, aerosols, advection, convection, diffusion, wet deposition, dry deposition, emissions, the stratosphere, the ocean, ... Modeled chemistry has been questioned (Olson 2006, Bertram 2007, Ren 2008) typically : evaluate a model against a chamber study (i.e. a controlled timeseries of measurements) problem : does anyone have a chamber at 236K and 0.298 atm? What to do? We need a timeseries of observations 1 We need a timeseries of model results 2 Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 3/16

Bertram results can derive air parcel ages Deep convection sends a plug of surface air to upper troposphere wet scavenging removes HNO 3 and lightning adds NO x Air parcels are mostly stable for up to 5 days Freshly convected: NO x :HNO 3 >> 1 Aged air parcel: NO x :HNO 3 << 1 Figure 3: Deep convection from Bertram et al. Science 2007 Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 4/16

Observation timeseries: classified by “derived age” 1000 10.0 5.0 3.0 NO x : HNO 3 2.0 1.0 0.5 0.3 0.2 0.1 initial 1 3 5 Figure 4: NO x :HNO 3 is used to categorize days since convection. O 3 shows a monotonic increase with time. CO shows a monotonic decrease with time. NO 2 shows a gradual increase with time. Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 5/16

Observation timeseries: classified by “derived age” 1000 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 Figure 4: NO x :HNO 3 is used to categorize days since convection. O 3 shows a monotonic increase with time. CO shows a monotonic decrease with time. NO 2 shows a gradual increase with time. Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 5/16

Observation timeseries: classified by “derived age” 1000 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 200 180 160 140 CO ppb 120 100 80 60 40 initial 1 3 5 Figure 4: NO x :HNO 3 is used to categorize days since convection. O 3 shows a monotonic increase with time. CO shows a monotonic decrease with time. NO 2 shows a gradual increase with time. Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 5/16

Observation timeseries: classified by “derived age” 1000 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 200 0 . 5 180 0 . 4 160 NO 2 / NO y 140 CO ppb 0 . 3 120 100 0 . 2 80 60 0 . 1 40 0 . 0 initial 1 3 5 initial 1 3 5 Figure 4: NO x :HNO 3 is used to categorize days since convection. O 3 shows a monotonic increase with time. CO shows a monotonic decrease with time. NO 2 shows a gradual increase with time. Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 5/16

Simulating aging of freshly convected air parcels Box modeling air parcels using LEEDS DSMACC box model Physical and initial conditions from “freshly convected” observations Table 1: Overview of 7 chemical mechanisms in this study. Model (abbreviation) ♯ Rxns ♯ Spcs Carbon Bond ‘05 (CB05) 176 62 State Air Pollution Research Center ‘99 222 77 (SAPRC99) SAPRC ‘07 (SAPRC07) < 700 153 Model for OZone And Related chemical 290 88 Tracers “Standard” (MZ4) GEOS-Chem “full” (GEOS) 290 88 Regional Atmospheric Chemistry Mech v.2 341 117 (RACM2) Master Chemical Mechanism (MCM) > 4500 > 1700 Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 6/16

Chemical Model Evaluation CB05 SAPRC99 SAPRC07 GEOS MZ4 RACM2 MCM 0 . 5 10.0 5.0 3.0 NO x : HNO 3 2.0 1.0 0.5 0.3 0.2 0.1 initial 1 3 5 Figure 5: Model predictions compared to observations with the Mann-Whitney U test. Model medians are displayed circles that are filled when consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 7/16

Chemical Model Evaluation CB05 SAPRC99 SAPRC07 GEOS MZ4 RACM2 MCM 0 . 5 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 Figure 5: Model predictions compared to observations with the Mann-Whitney U test. Model medians are displayed circles that are filled when consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 7/16

Chemical Model Evaluation CB05 SAPRC99 SAPRC07 GEOS MZ4 RACM2 MCM 0 . 5 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 200 180 160 CO ppb 140 120 100 80 60 40 initial 1 3 5 Figure 5: Model predictions compared to observations with the Mann-Whitney U test. Model medians are displayed circles that are filled when consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 7/16

Chemical Model Evaluation CB05 SAPRC99 SAPRC07 GEOS MZ4 RACM2 MCM 0 . 5 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 200 0 . 5 180 0 . 4 160 NO 2 / NO y CO ppb 140 0 . 3 120 100 0 . 2 80 60 0 . 1 40 0 . 0 initial 1 3 5 initial 1 3 5 Figure 5: Model predictions compared to observations with the Mann-Whitney U test. Model medians are displayed circles that are filled when consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 7/16

Models over-predict NO 2 /NO x , PAN, and HNO 3 CB05 SAPRC99 SAPRC07 GEOS MZ4 RACM2 MCM 10.0 0 . 8 5.0 0 . 7 NO y fraction 3.0 NO x : HNO 3 0 . 6 2.0 0 . 5 1.0 0 . 4 0.5 0 . 3 0.3 0 . 2 0.2 0 . 1 0.1 0 . 0 NO x : HNO 3 NO NO 2 HNO 4 PANS HNO 3 NTRS fresh old 0 12 24 48 72 96 120 Figure 6: Nitrogen species 24 hours since convection: observed (back) and modeled (front). Filled circles are consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 8/16

Conclusions: Model performance Semi-explicit, regional, and global models all under-predict NO x :HNO 3 under-prediction NO x over-predict NO z , esp. CH 3 C(O)ONO 2 and HNO 3 over-prediction NO 2 /NO x All problems point to too many radical reactions Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 9/16

PAN Sensitivity Studies IUPAC97 GEOS 2xCO ALD2 0 . 5 10.0 200 180 5.0 160 3.0 NO x : HNO 3 140 2.0 O 3 ppb 120 1.0 100 0.5 80 0.3 60 0.2 40 0.1 initial 1 3 5 initial 1 3 5 200 0 . 8 180 0 . 7 160 0 . 6 PAN / NO y CO ppb 140 0 . 5 120 0 . 4 100 0 . 3 80 0 . 2 60 0 . 1 40 0 . 0 initial 1 3 5 initial 1 3 5 Figure 7: GEOS-Chem tested with old acetone quantum yield, with 2xCO, and with constrained acetaldehyde. Model medians are displayed circles that are filled when consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 10/16

Models over-predict OH and HO 2 CB05 SAPRC99 SAPRC07 GEOS MZ4 RACM2 MCM 0 . 8 18 16 0 . 7 14 0 . 6 HO 2 ppt OH ppt 12 0 . 5 10 0 . 4 8 0 . 3 6 0 . 2 4 0 . 1 2 15-30 30-45 45-60 60-75 15-30 30-45 45-60 60-75 fresh old 0 12 24 48 72 96 120 Figure 8: HOx · by solar zenith angle 24 hours since convection: observed (back) and modeled (front). Filled circles are consistent with observations (p < 0.0001). Barron Henderson, MS, ORISE Research Fellow Upper troposphere NO 2 under-predictions 11/16