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SOME CHEMICAL PROBLEMS IN ATMOSPHERIC CHEMISTRY MODELS. Daniel J. Jacob. with in order of appearance: Rokjin Park, Colette L. Heald (now at UC Berkeley), Tzung-May Fu, Paul I. Palmer (now at U. Leeds), Dylan B. Millet, Rynda C. Hudman, Noelle E. Selin, Christopher D. Holmes.

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some chemical problems in atmospheric chemistry models
SOME CHEMICAL PROBLEMS IN ATMOSPHERIC CHEMISTRY MODELS

Daniel J. Jacob

with in order of appearance: Rokjin Park, Colette L. Heald (now at UC Berkeley), Tzung-May Fu, Paul I. Palmer (now at U. Leeds), Dylan B. Millet, Rynda C. Hudman, Noelle E. Selin, Christopher D. Holmes

…and funding from EPRI, EPA, NSF, NASA

geos chem global 3 d chemical transport model
GEOS-Chem GLOBAL 3-D CHEMICAL TRANSPORT MODEL
  • Driven by assimilated meteorological data from NASA Global Modeling and Assimilation Office (GMAO) with 3-6 hour resolution
  • Horizontal resolution 1ox1o to 4ox5o , ~50 vertical layers
  • Applied to wide range of problems: tropospheric oxidants, aerosols, CO2, methane, hydrogen, mercury, exotic species…by over 20 groups in N. America, Europe, Australia
  • Flagship tropospheric ozone-aerosol simulation includes ~120 coupled species, ~500 chemical reactions
  • Serves grander purposes: (1) boundary conditions for EPA CMAQ regional model , (2) global chemical data assimilation at GMAO, (3) effects of climate change through interface with GISS GCM, (4) construction of Earth system model through NASA/GMI
our first organic carbon oc simulation for the united states
IMPROVE obs (1998)OUR FIRST ORGANIC CARBON (OC) SIMULATION FOR THE UNITED STATES

Park et al. [2003]

annual

U.S. source:

2.7 Tg yr-1

10%

terpenes

first mass concentration measurements of oc aerosols in free troposphere
Observed (Huebert)

GEOS-Chem

(Chung & Seinfeld

for SOA)

FIRST MASS CONCENTRATION MEASUREMENTSOF OC AEROSOLS IN FREE TROPOSPHERE

ACE-Asia aircraft data over Japan (April-May 2001)

Observed

(Russell)

Chung and Seinfeld scheme:

OC/sulfate ratio

  • Observations show 1-3 mg m-3 background;
  • model too low by factor 10-100

Heald et al. [2005]

itct 2k4 aircraft campaign over eastern u s in july august 2004
ITCT-2K4 AIRCRAFT CAMPAIGN OVER EASTERN U.S. IN JULY-AUGUST 2004

water-soluble organic carbon (WSOC) aerosol measurements

by Rodney J. Weber (Georgia Tech)

Alaska

fire

plumes

2-6 km altitude

Values ~2x lower than observed in ACE-Asia; excluding fire plumes

gives mean of 1.0 mgC m-3 (3x lower than ACE-Asia)

Heald et al., in prep.

model oc aerosol sources during itct 2k4
~10% yield

~2% yield

MODEL OC AEROSOL SOURCES DURING ITCT-2K4

Large fires in Alaska

and NW Canada:

60% of fire emissions

released above 2 km

(pyro-convection)

Heald et al., in prep.

itct 2k4 oc aerosol vertical profiles
ITCT-2K4 OC AEROSOL: VERTICAL PROFILES

Total

Biomass burning

Anthropogenic

Biogenic SOA

Observations

Model

hydro-

phobic

SOx = SO2 + SO42-:

efficient scavenging

during boundary layer

ventilation

Data filtered against

fire plumes (solid)

and unfiltered (dotted)

Model source attribution

Heald et al., in prep.

correlation of observed free tropospheric wsoc with other chemical variables in itct 2k4
CORRELATION OF OBSERVED FREE TROPOSPHERIC WSOCWITH OTHER CHEMICAL VARIABLES IN ITCT-2K4

No single variable gives R > 0.37, but toluene bivariate correlations with

sulfate, acetic acid, and HNO3 give R > 0.7. No correlation with isoprene oxidation products

Suggest aqueous-phase mechanism involving aromatics

Heald et al., in prep.

alternate mechanism for soa formation aqueous phase oxidation and polymerization of dicarbonyls
ALTERNATE MECHANISM FOR SOA FORMATION:AQUEOUS-PHASE OXIDATION AND POLYMERIZATION OF DICARBONYLS

Isoprene

350 TgC/yr * (Y ~ 4.5%)

= 16 TgC/yr

AQUEOUS PHASE

H* = 4x105 M atm-1

glyoxal

Monoterpenes

100 TgC/yr * (Y ~ 0.09%) = 0.9 TgC/yr

CHOCHO

CH(OH)2CH(OH)2

t ~ 1.3 h

Aromatics

20 TgC/yr * (Y~ 20%)

= 4 TgC/yr

Oxidation

Polymerization

Oxidation by OH

Photolysis

Deposition

Liggio et al. [2005],

Lim et al. [2005],

Hastings et al. [2005]

Kroll et al. [2005]

model representation of aqueous phase soa formation using reaction probability g applied to glyoxal
MODEL REPRESENTATION OF AQUEOUS-PHASE SOA FORMATION USING REACTION PROBABILITY g APPLIED TO GLYOXAL

Liggio et al. [2005]

geos chem glyoxal and methylglyoxal in surface air july
Production: isoprene, monoterpene, aromatics

Loss: photolysis, oxidation

No aerosol uptake, dry/wet deposition yet

GEOS-Chem glyoxal and methylglyoxal in surface air (July)

GLYX [ppb] at 0E

Z (km)

0.28 ppb

MGLY [ppb] at 0E

Z (km)

0.56 ppb

Tzung-May Fu, Harvard

oxygenated vocs over tropical pacific pem tropics b data
OXYGENATED VOCs OVER TROPICAL PACIFIC (PEM-TROPICS B DATA)

SH

Singh et al. [2001]

Methanol and acetone are

the principal contributors

NH

slide13
GLOBAL MODEL BUDGET OF METHANOL (Tg yr-1)with (in parentheses) ranges of previous budgets from Singh et al. [2000],Heikes et al. [2002], Galbally and Kirstine [2003], Tie et al. [2003]

CH3O2 (85%)

RO2 (15%)

OH

CH3OH

lifetime 10 days

(5-12)

130

VOC

CH3O2

Atmospheric

production:

37(18-31)

OH(aq) - clouds

<1(5-10)

Dry dep. (land) : 56

Wet dep.: 12

NPP based,

x3 for young

leaves

Ocean

uptake:

11 (0-50)

Plant growth:

128 (50-312)

Urban:

4 (3-8)

Biomass burning:

9 (6-13)

Biofuels:

3

Plant decay:

23 (13-20)

Jacob et al. [2005]

simulated methanol concentrations in surface air
SIMULATED METHANOL CONCENTRATIONS IN SURFACE AIR
  • Representative observations
  • In ppbv [Heikes et al., 2002]:
  • Urban: 20 (<1-47)
  • Forests: 10 (1-37)
  • Grasslands: 6 (4-9)
  • Cont. background: 2 (1-4)
  • NH oceans: 0.9 (0.3-1.4)

Tropics: obs model

Rondonia 1-6 10

Costa Rica 2.2 2.1

Jacob et al. [2005]

methanol vertical profiles over s pacific
0 0.6 1.2 1.8 2.4 3

0 0.6 1.2 1.8 2.4 3

0 0.6 1.2 1.8 2.4 3

Methanol, ppbv

model atmospheric source

METHANOL VERTICAL PROFILES OVER S. PACIFIC

obs. From

H.B. Singh

Could the atmospheric source from CH3O2 + CH3O2 be underestimated?

HO2

CH3OOH

~ 70%

OH

In model over S. Pacific,

NO

CH4

CH3O2

~ 20%

HCHO

CH3O2

5-10%

0.6 CH3OH +…

Photochemical model calculations for same data set [Olson et al., 2001] are

50% too high for CH3OOH, factor of 2 too low for HCHO

Could there be a biogenic VOC “soup” driving organic and HOx chemistry

in the remote troposphere?

Jacob et al. [2005]

slide16

GLOBAL GEOS-CHEM BUDGET OF ACETONE (Tg yr-1)from Jacob et al. [2002]with photolysis update from Blitz et al. [2004]

hn

propane

i-butane

OH

(CH3)2CO

lifetime 15 days

18 days

46

28

21 (16-26)

OH

OH, O3

terpenes

MBO

7 (3-11)

27

37

Dry dep. (land) : 9

12

Ocean

uptake:

14 19

Ocean

source:

27 (21-33)

microbes

DOC+hv

Urban:

1 (1-2)

Vegetation:

33 (22-42)

Biomass burning:

5 (3-7)

Plant decay:

2 (-3 - 7)

oceanic source of acetone in model needed to match observations over s pacific
a priori sources/sinks; c2 = 1.3

Optimized sources/sinks

(including “microbial” ocean sink,

photochemical ocean source); c2 = 0.39

OCEANIC SOURCE OF ACETONE IN MODELNEEDED TO MATCH OBSERVATIONS OVER S. PACIFIC

from Jacob et al. [2002]

obs from Solberg et al.

[1996]

obs. From

H.B. Singh

but more recent aircraft data imply a net oceanic sink for acetone
Observed

Model

…BUT MORE RECENT AIRCRAFT DATA IMPLY A NET OCEANIC SINK FOR ACETONE

TRACE-P observations over tropical North Pacific in spring [Singh et al., 2003]

slide19
CORRELATION OF ACETONE WITH TRACERS OF SOURCES IN ASIAN OUTFLOW (TRACE-P DATA)

Multiple regression:

Continental

source

Propane source

Acetone = b0

+ b1 [Ethane]

+ b2 [HCN]

+ b3 [Methanol]

Acetone [pptv]

Acetone [pptv]

Intercept = 200 pptv

Ethane [pptv]

CO [pptv]

Acetone = b0

+ b1 [CO]

+ b2 [HCN]

+ b3 [Methanol]

Biomass

burning

source

Acetone [pptv]

Acetone [pptv]

Biogenic

source

Intercept = 238 pptv

How to explain the

pervasive 200 pptv

acetone background?

HCN [pptv]

Methanol [pptv]

Tzung-May Fu (Harvard)

hcho column data from omi satellite instrument
HCHO COLUMN DATA FROM OMI SATELLITE INSTRUMENT

July 2005

Thomas Kurosu (Harvard/SAO) and Dylan Millet (Harvard)

space based measurements of hcho columns as constraints on volatile organic compound voc emissions
SPACE-BASED MEASUREMENTS OF HCHO COLUMNSAS CONSTRAINTS ON VOLATILE ORGANIC COMPOUND (VOC) EMISSIONS
  • VOCs important as
  • precursors of tropospheric ozone
  • precursors of organic aerosols
  • sinks of OH

340 nm

hn (l < 345 nm), OH

Oxidation (OH, O3, NO3)

VOC

HCHO

lifetime of hours

several steps

Vegetation Anthropogenic Biomass burning

~1000 ~200 ~100 Tg C yr-1

relating hcho columns to voc emission
RELATING HCHO COLUMNS TO VOC EMISSION

hn (<345 nm), OH

oxn.

VOCi

HCHO

yield yi

k ~ 0.5 h-1

Emission Ei

smearing, displacement

In absence of horizontal wind, mass balance for HCHO column WHCHO:

Local linear relationship

between HCHO and E

… but wind smears this local relationship between WHCHO and Ei depending on the lifetime of the parent VOC with respect to HCHO production:

Isoprene

WHCHO

a-pinene

propane

Distance downwind

100 km

VOC source

time dependent hcho yields from voc oxidation
Box model simulations with state-of-science MCM v3.1 mechanismTIME-DEPENDENT HCHO YIELDS FROM VOC OXIDATION

methylbutenol

High HCHO signal from isoprene with little smearing,

weak and smeared signal from terpenes;

GEOS-Chem yields from isoprene may be too low by 10-40% depending on NOx

Palmer et al, [2006]

hcho yields from isoprene oxidation
observed

m = 3.3

WHCHO, 1016 cm-2

GEOS-Chem

m = 3.5

WISOP, 1016 cm-2

Sensitivity to peroxide recycling

(standard model assumes recycling)

HCHO YIELDS FROM ISOPRENE OXIDATION

HCHO vs. isoprene columns

in INTEX-A

Ultimate

HCHO yield

INTEX-A observations imply a per carbon yield of 0.32 ± 0.1

Palmer et al. [2003], Millet et al. [2006]

radical chemistry in upper troposphere intex a aircraft data over southeast u s jul aug 04
RADICAL CHEMISTRY IN UPPER TROPOSPHERE:INTEX-A aircraft data over southeast U.S. (Jul-Aug 04)

OH

O3

HO2

NOx

Black: observations by Cohen (NO2), Avery (ozone), Brune (HO2 and OH)

Red: standard model simulation

Green: model simulation with 4x lightning

Fixing NOx (and ozone!) results in 3x overestimate of OH in upper troposphere;

IF we could fix OH, the NOx and ozone underestimates would fix themselves…

Hudman et al. (in prep.)

bro x chemistry in troposphere
BrOx CHEMISTRY IN TROPOSPHERE

Yang et al. [2005] global model including bromocarbon oxidation/photolysis and sea salt debromination

Satellites observe 0.5-2pptv BrO

in excess of what stratospheric

models can explain.

Tropospheric BrO ?

due to Arctic BL spring bloom

Significant consequences for tropospheric ozone and NOx budgets

mercury in the atmosphere
REACTIVE GASEOUS

MERCURY (RGM)

MERCURY IN THE ATMOSPHERE

TOTAL GASEOUS MERCURY (TGM)

Hg(II)

(gas)

Hg(0)

(gas)

Oxidation

OH, O3, Br(?)

VERY

SOLUBLE

RELATIVELY INSOLUBLE

ATMOSPHERIC LIFETIME:

ABOUT 1 YEAR

TYPICAL LEVELS:

1.7 ng m-3

Reduction

Photochemical aqueous (?)

Hg(II)

(aqueous)

Hg(P)

(solid)

LIFETIME: DAYS TO WEEKS

TYPICAL LEVELS: 1-100 pg m-3

DRY AND WET DEPOSITION

EMITTED BY COAL-

FIRED POWER PLANTS

ECOSYSTEM INPUTS

large uncertainty in atmospheric hg chemistry
[cm3 s-1]

8.7(±2.8) x 10-14Sommar et al., AE 2001

9.0(±1.3) x 10-14Pal & Ariya, ES&T 2004

much slower Calvert & Lindberg, AE 2005

3(±2) x 10-20Hall, WASP 1995

1.7 x 10-18 Iverfeldt & Lindqvist, AE 198

[cm3 s-1]

LARGE UNCERTAINTY IN ATMOSPHERIC Hg CHEMISTRY

In standard GEOS-Chem, 80% of

Hg(0) oxidation is by OH; 60% of produced Hg(II) is reduced back to Hg(0) photochemically in clouds

Large discrepancies in reported rates!

(parenthetical reactions not in model)

Deposition

rapid conversion of hg 0 to hg ii in arctic spring observation of mercury depletion events mdes
RAPID CONVERSION OF Hg(0) to Hg(II) IN ARCTIC SPRINGObservation ofMercury Depletion Events (MDEs)

Br

Br, OH

1

3

Hg0

HgBr

HgBrX

2

Goodsite et al., ES&T 2005

T

MDEs correlate with ODEs and reactive halogens (up to 30pptv BrO).

Spitzbergen: Sprovieri et al., ES&T 2005

evidence for oxidation of hg 0 by br in marine boundary layer
Observations

GEOS-Chem (OH,O3)

EVIDENCE FOR OXIDATION OF Hg(0) BY Br IN MARINE BOUNDARY LAYER

Residual diurnal cycle of Hg(0) observed at Okinawa in April

Consistent with Br release from

Br2 or HOBr at sunrise

Jaffe et al [2005]; Selin et al. [2006]

could br be the missing global hg 0 oxidant
COULD Br BE THE MISSING GLOBAL Hg(0) OXIDANT?

Br mixing ratio (Yang et al., 2005)

Hg0 Lifetime

Global lifetime of Hg(0) against oxidation by Br: 0.6 y (range 0.2-1.6 y);

Compare to observational constraint of ~1 y for Hg lifetime against deposition

Holmes et al., GRL 2006

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