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Qiaoqiao Wang, Kevin Wecht, Daniel Jacob

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1 Using HIPPO observations to constrain the atmospheric budgets of black carbon (BC) and methane
Qiaoqiao Wang, Kevin Wecht, Daniel Jacob Anne Perring, Joshua Schwarz, Ryan Spackman, David Fahey NOAA Eric Kort, Steven Wofsy Harvard University With support from NSF (HIPPO), NASA (ACMAP, CMS) 1

2 AeroCom models show large errors for BC in remote air
Multimodel intercomparisons and comparisons to observations Multimodel intercomparison and comparison to observations AeroCom models show large errors for BC in remote air ARCTAS (Arctic spring) TC4 (Costa Rica, summer) Observed Models Pressure, hPa BC, ng kg-1 BC, ng kg-1 HIPPO over Pacific (Jan) Models differ by order of magnitude between themselves and with observations Discrepancy must be driven by model errors in scavenging Pressure, hPa obs models 20S-20N obs models 60-80N BC, ng kg-1 BC, ng kg-1 Koch et al. [2009], Schwarz et al. [2010]

3 Global BC simulation in GEOS-Chem
2ox2.5o horizontal resolution, GEOS-5 assimilated meteorological data 2009 emissions x2 x0.7 Steven Barrett , Federal aviation administration; The dataset was generated using the Aviation Emissions Inventory Code (AEIC). Anthropogenic emission dominates globally, biomass burning may dominate regionally and seasonally GFED3 Bond et al. [2007], scaled Anthropogenic ≡ fossil fuel + biofuel

4 Previous application to Arctic spring (ARCTAS)
GEOS-Chem aerosol scavenging scheme Cloud updraft scavenging Anvil precipitation Large scale precipitation CCN IN+CCN CCN+IN, impaction Below-cloud scavenging (accumulation mode aerosol), different for rain and snow Partial or complete re-evaporation (virga) entrainment BC has 1-day time scale for conversion from hydrophobic (non-CCN) to hydrophilic detrainment vertical position of the aerosol particle, the scavenging process can be in-cloud or below-cloud. In-cloud: aerosols enter cloud droplets or ice crystals when they act as cloud condensation or ice nuclei and also by the process of impaction with the cloud droplets and crystals Below-cloud: is the capture of aerosol particles by precipitating rain droplets or snow particles, and is usually described by a first order decay equation. No systematic biases when compared to aerosol observations 210Pb tropospheric lifetime of 8.6 days (consistent with best estimate of 9 days)

5 Testing model BC emissions with observed surface air concentrations in source regions
NMB= -27% Circles: annual mean observations (2006 in China, in Europe, 2009 in US) Solid contours: model Model is too low by 10-30% - small error for our purposes NMB= 6.6% Underestimation in Europe is mainly due to three sites in northern Italy and Belgium. Without these three sites the NMB would decrease to -0.7%. NMB= -12%

6 Previous GEOS-Chem evaluation in Arctic winter-spring
Mean ARCTAS aircraft profile, April 2008 Model vs. observed snow BC content, Surface concentrations at Barrow, 2008 Observed Model Russia fuel Dominant BC contributions from fuel in N American Arctic, fires in Russian Arctic Russia fuel source higher than expected Wang et al. [2011]

7 HIPPO BC curtains across Pacific
Observed Model Jan 09 Oct-Nov 09 Mar-Apr 10 Concentrations are lowest in the deep tropics (scavenging) SH concentrations are highest in Oct-Nov (open fires) but remain higher than tropics in other seasons (fuel sources)

8 Latitudinal dependence of BC concentrations
Geometric mean ±sd vs. latitude Latitudinal dependence of BC concentrations Observed Model Secondary maximum in southern extratropics reflects significant anthropogenic source, seasonal amplification by open fires Model tends to overestimate low end of observations and is unable to reproduce frequent observed concentrations <0.05 ng m-3 STP in the deep tropics Discrepancy suggests insufficient scavenging in very old air; implication for indirect radiative effect? NMB = +11% Model vs. observed BC

9 BC and CO are correlated in fire seasons but not otherwise
Oct-Nov 20-60S Jan 20-60N Over the tropics, within 10% (30%) Arctic, % higher Lack of BC-CO correlation outside of fire seasons reflects diversity of sources, large lifetime difference

10 Seasonal mean BC vertical profiles from HIPPO 1-3
Mid-latitudes show peak in mid-troposphere from WCB lifting Highest concentrations in NH in spring when WCB lifting is most frequent General decrease with altitude in the tropics due to deep convective scavenging

11 Zonal mean BC in GEOS-Chem
Zonal annual mean BC concentrations in GEOS-Chem Pressure, hPa The annual global burden of BC in the troposphere  is 74 Gg, 34% of which is present in the free troposphere (>2 km). Only 23% of the burden is in SH. The annual global contribution of fire emissions to BC burden is 30%, with most fire emissions originate in Africa, accounting for 69% of fire BC in the troposphere. Anthropogenic BC in the atmosphere is mainly from NH, accounting for more than 80%, with similar regional contributions as those to anthropogenic emission.   34% of BC mass is in free troposphere (> 2 km): expect large radiative forcing implications (stay tuned!)

12 Methane in HIPPO: enabling inverse models of sources
1. Model evaluation and error correlation length scales HIPPO-3, Mar-Apr 2010 southbound northbound 200 600 1000 Observed Pressure, hPa 200 600 1000 GEOS-Chem prior 50S N S N 2. TES v5 satellite instrument validation: two pieces of info for methane 100 1000 10 Pressure, hPa Bias: lat-dep ±29 ppb Bias: 42 ±27 ppb Averaging kernel Wecht et al. [2012]

13 Correction factors for GEOS-Chem emissions from preliminary inversion
Using satellite observations in adjoint inversion of methane emissions in North America GEOS-Chem nested model (0.5ox0.67o) with HIPPO-tested boundary conditions SCIAMACHY mixing ratios (Jul-Aug 2004) 1700 1800 ppb Correction factors for GEOS-Chem emissions from preliminary inversion EPA emission inventory underestimates emissions from oil/gas, livestock GEOS-Chem wetland emissions (Kaplan) are too high Inversion is underconstrained on 0.5ox0.67o model grid; spatial clustering is necessary (stay tuned!) 0.8 1.2


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