U N I V E R S I T Y O F W A S H I N G T O N S C H O O L O F N U R S I N G Sensitivity of surface O 3 to soil NO x emissions over the U.S. Lyatt Jaeglé Department of Atmospheric Sciences University of Washington + New formulation of HO 2 uptake on aerosols  Joel Thornton + H 2 and  D simulation  Heather Price O 3 increase due to soils New  HO2 H 2 and  D

Soil NOx emissions inferred from GOME NO 2 A posteriori (8.9 TgN/yr) ~70% larger than a priori A priori A posteriori Largest soil emissions: seasonally dry tropical ecosystems (±200%) (±90%) Jaeglé et al. (2005) + fertilized cropland ecosystems What are the implications for surface O 3 over N. America?  Sensitivity to doubling of soil NOx for dry ecosystems + fertilizer US: soil NOx increased by 85% Summer (JJA): soils = 0.6 TgN vs. anthropogenic US = 1.4 TgN atoms N cm -2 s -1

High soil: Surface O 3 Standard: Surface O 3  3-7 ppbv increase in O 3 over Great Plains+SW  Is this consistent with AIRS surface O 3 observations? 1-5 pm Effects on surface O 3 over the U.S. (JJA 2001) High soil - Standard ppbv AIRS Observations: O pm ppbv

High soil – AIRS O 3 Standard – AIRS O 3 Comparison to AIRS observations (JJA 2001) ppbv  Reduced model bias over Great Plains from –3.5 to +0.6 ppbv Model bias -3.5 ppbv Model bias +0.6 ppbv 1-5 pm

Standard Model Enhanced Soil Model Daily variations in surface O 3 Enhanced-Standard O 3 (ppbv) AIRS observations Model with no soil emissions  Overall, soil emissions increase O 3 by 7- 8 ppbv + double modeled variance 1-5pm 2001

Heterogeneous uptake of HO 2 on aerosols Thornton, Jaeglé & McNeill (2007) Latitude Low  HO2 (<0.05) in LT High  HO2 (>0.1) in cold UT If dissolved Cu(II) ions present:  HO2 > 0.2 [ Mozurkewich et al. 1987] Without Cu(II) ions:  HO2 =f(temp, aerosol radius, pH) [ Thornton and Abbatt, 2005] Surface  HO2 Zonal mean  HO2  Implement new  HO2 = f(temp, r, pH=5) in GEOS-Chem for all aerosols except dust (  HO2=0.2)  HO2 <0.005 in Tropics (temp) + industrialized/BB regions (r)

Effects of HO 2 uptake on oxidants New  HO2 % change relative to  HO2 =0  HO 2 (%) -1 to -5%  H 2 O 2 (%) +1 to 10% Altitude (km)  HO2 = to -25% +5 to 30%  HO 2 (%)  H 2 O 2 (%) Altitude (km) Tie et al. [2001,2005] Martin et al. [2003] Tang et al. [2003]  HO2 >0.1 overestimates effects on oxidants? HO 2  0.5 H 2 O 2 aerosols

What  HO2 to use? Not enough Cu(II) in aerosols for high  HO2 ?  IMPROVE [Thornton et al., 2007], NEAQS [Murphy, 2007] New  HO2 consistent with comparisons to obs  High in UT [Jaeglé et al., 2000], low in LT over US [Hudman et al., 2007] and over BB regions [Sauvage et al., 2007] … but inconsistent with  HO2 >0.1 inferred from HO x obs  MBL over Mauna Loa [Cantrell et al.,1996], Cape Grim [Sommariva et al., 2004; Haggerstone et al., 2005], Mace Head [Smith et al., 2006]. Halogen chemistry? GEOS-Chem:  HO2 =0.2 (v4-30, Mar ‘02-Jun ‘06)  HO2 =0 (v and higher)  Implement new formulation? INTEX-A H2O2H2O2  HO2 =0.2 +

 D(H 2 ): DJF Photochemical production (162  57‰) + stratospheric transport (34‰) H 2 and  D simulation in GEOS-Chem Price et al., JGR, 2007 H 2 : SON Soil sink (55  9 Tg yr -1 ) Ocean source (6  3 Tg yr -1 ) Observations: H 2 -- CMDL ground sites + aircraft, Novelli et al. (1999)  D -- cruises from Gerst & Quay (2000), Rice & Quay (2007) H 2 (ppbv) Altitude (km) H 2 profile: Poker Flat, Alaska

Summary Increased soil NO x emissions consistent with observed surface O 3 over Great Plains New  HO2 formulation  HO2 >0.1 in UT, but  HO2 <0.01 in LT Simultaneous constraints on H 2 and  D budget: soil sink, ocean source, and isotopic signatures.

How much copper is there in aerosols? Cu(II) Solute Mass Fraction  90% of the observations, Cu mass fraction < 3x10 -4  50% of the observations, Cu mass fraction < 8x E-51E-41E IMPROVE Cu fine mode mass fraction Cumulative frequency distribution Threshold for Cu-catalyzed HOx loss