Two puzzles of atmospheric chemistry over the Southeast US

Jingqiu Mao (AOS/GFDL), Larry Horowitz (GFDL), Vaishali Naik (GFDL), Fabien Paulot (Harvard), Paul Ginoux(GFDL), Meiyun Lin (GFDL), Arlene Fiore (Columbia U) and the SENEX science team

Funding from NOAA CPO

What is so unique for Southeast US?

(Millet et al., 2008, JGR)(Martin et al., 2008, AE)

Surface NOx is mainly produced from anthropogenic activities

HCHO is mainly produced from biogenic emissions (isoprene in particular)

Anthropogenic + Natural

Volatile organic compounds (VOCs) in the atmosphere:carbon oxidation chain

VOC RO2

NO2

O3

organicperoxyradicals

NO

h

carbonyls R’O2

h

OH + products

organic aerosol

ROOHorganicperoxides

OHHO

2

OH, h

OH

products

EARTH SURFACE

biospherecombustionindustry

deposition

Increasing functionality & cleavage• sources of organic aerosol• sources/sinks of oxidants (ozone, OH)

OVOCs

Importance of NOx

Global Budget of Organic Aerosols

fuel/industry open fires

OH, O3,NO3 SOG SOA

POA

K

vegetation fuel/industry open fires

700

isopreneterpenesoxygenates…

30 alkenesaromaticsoxygenates…

VOC EMISSION PRIMARY EMISSION

VOC

50 20 100

20Global sources in Tg C y-1

Two-product

SOA ≡ secondary organic aerosolPOA ≡ primary organic aerosol

Current AM3 treats SOA production as yield of terpene emissions.

Aqueous reactions

?

?

Uptake on cloud droplets

or aerosols

Puzzle 1: Overestimate of ozone

Summertime ozone over eastern US is a problem for most models

(Fiore et al., 2009, JGR)

Multimodel mean

Obs from CASTNET surface sites

Northeast US

Southeast US

Multimodel mean

Obs from CASTNET surface sites

Standard AM3

(Naik et al., 2013, JGR, in press)

Similar bias was found for the maximum daily 8-hour average ozone comparison.

Overestimate of ozone is likely a chemistry problem

Previous models with assimilated meteorology field (CTM) show similar overestimate.

Models with higher resolution also show similar overestimate.

Fiore et al. (2005) attributed this bias to the treatment of isoprene chemistry in the model.

(Rasmussen et al., 2012, AE)

Puzzle 2 : Aerosols and regional cooling

Temperature trend over past century

(Portmann et al., 2009, PNAS)

1950-2006 for May-June (Unit: K/Decade)

(Leibensperger et al., 2012, ACP)

This temperature trend cannot be explained by the change in precipitation or dynamic patterns (El Niňo, NAO) (Portmann et al., 2009).

1930-1990 change in Annual Mean Surface Temperature

The cooling can be partially due to secondary organic aerosols

(Goldstein et al., PNAS, 2009)

MISR aerosol optical thickness (diff. between JJA and DJF)

MODIS aerosol optical thickness (diff. between JJA and DJF)

(Ford et al., 2013, ACPD)

Current hypothesis is that large amount of organic aerosols are produced above the surface layer.

Similar problem was found in GFDL models

(Courtesy of Paul Ginoux and Ilissa Ocko)

Optical properties from aircraft data (left) and the model (right) over Oklahoma, US

Model cannot reproduce high loading of aerosols above the surface layer!

CM 2.1

CM 3

Geophysical Fluid Dynamics Laboratory

Surface Air Temperature

OBS (GISS)

K

Stronger cooling at northern mid-latitudes in CM3, 3x less warming globally examine forcings

CM2.1

CM3

Years (1961-2000) minus (1881-1920)

(Courtesy of Larry Horowitz)

Underestimate of organic aerosol is also a chemistry problem

(Ford et al., 2013, ACPD)

Current models cannot reproduce such amount of aerosols above the surface layer.

This cannot be explained by PBL height, SO2 emissions.

New development of chemistry in AM3: (1) heterogeneous chemistry

dust

SO4

BC

OC

Standard AM3

Updated AM3

N2O5, HO2

SO4

SeaSalt

N2O5, HO2, NO3, NO2

A new framework for heterogeneous chemistry

RH(%) 0 50 70 80 90 95 99

SO4 1.0 1.4 1.5 1.6 1.8 1.9 2.2

OC 1.0 1.2 1.4 1.5 1.6 1.8 2.2BC 1.0 1.0 1.0 1.2 1.4 1.5 1.9Sea salt

1.0 1.6 1.8 2.0 2.4 2.9 4.8

Reactions Uptake coefficient (γ)

HO2 → products 1.0

N2O5 → 2.0 HNO3 0.1

NO3 → 1.0 HNO3 0.1

NO2 → 0.5 HNO3 0.0001

Hygroscopic growth factor

(Mao et al., 2013a, ACP; 2013b, GRL)

Impact of heterogeneous chemistry (AM3 C48 2001-2005)

(Mao et al., 2013a, ACP; 2013b, GRL)

Simulation (het chem on) – Simulation (het chem off)

Improvement on CO at 500 hPa

AM3 with het chem off

MOPITT

AM3 with het chem on

MOPITT (2000-2004) AM3(2001-2005)

Improvement on OH ratio (NH/SH)

obs

(Naik et al., 2013, JGR, in press)

The impact of biomass burning emissions on global OH/ozone:Implications for radiative forcing

IPCC AR4 only estimates the direct forcing from biomass burning aerosols (+0.03 ±0.12 W m-2)

Aerosol uptake has large impact on ozone production efficiency

ΔO3/ ΔCO is a measure of ozone production efficiency.

Observations

Sensitivity of tropospheric oxidants to biomass burning emissions

Global OH decreases with larger bb emissions.

Global ozone increases with larger bb emissions.

(Mao et al., 2013b, GRL)

Nonlinearity of total radiative forcing on biomass burning strength

CH4-induced O3 and H2O

Steady state CH4

Chemical indirect forcing from CH4 and CH4-induced changes in O3 and stratosphericH2O, is comparable to the cooling from biomass burning aerosolswith direct and indirect effect taken into account.

How about chemical indirect forcing from anthropogenic emissions?

New development of chemistry in AM3: (2) a new isoprene chemistry scheme

A new isoprene oxidation mechanism for global models

(Mao et al., submitted to JGR)

NO

12

34

OH

11.7%

O

MVK

First generation isoprene nitrates

O

MACRH

O

H

HCHO

88%Organic peroxides

OHOO

OO

OH

-hydroxyl peroxy radicaland isomers

-hydroxyl peroxy radicaland isomers

71% 29%

HO2 1,6-H shif t isomerization

4.7%

7.3%

12%26% 40% 66%

HOOO

HPALDs

hvOH100%

100%

C2 and C3 carbonyl compounds

ISOPO2 ISOPO2

OH recycling from isoprene oxidation has been a hot topic in atmospheric chemistry community in last 5 years!

Global Emissions (Tg/yr)

0

200

400

600

Isoprene Methanol AllAnthropogenic

VOCs

Was OH really that high over SE US during ICARTT?

(Ren et al., 2008, JGR)

OH measured by traditional method during ICARTT 2004

(Mao et al., 2012, ACP)

Part of OH signal could be due to interference, probably from biogenic VOC oxidation products!

A new method of measuring OH was deployed in Blodgett Forest

First generation of isoprene nitrates degraded to second generation nitrates!OH

ONO2

ISOPN (1,4)

OHONO2

ISOPN (1,2)

OHONO2

ISOPN (4,3)

ONO2

OH

ISOPN (4,1)

O

OH

ONO2

methylvinylketone nitrate (MVKN)

O

ethanal nitrate(ETHLN)

O

propanone nitrate(PROPNN)

O

methacrolein nitrate(MACRN)

ONO2

OH

OH/O2

OH

ONO2

OHOO

NO

OH

ONO2

OHO

OHONO2

OHOO

NO

OHONO2

OHO

ONO2

OH

OHOO

NO

ONO2

OH

OHO

OHONO2

OHOO

NO

OHONO2

OHO

OH/O2OH/O2OH/O2

O2NO

O2NO

Second generation isoprene nitrates (C3-C4)

First generation isoprene nitrates (C5)

C5 alkyl nitrate is short-lived due to oxidation by OH and ozone, with photochemical lifetime of 2-3 hrs.

(Paulot et al., 2009a,b)

NOy budget in eastern U.S. boundary layer for July 2004

Species Emission Chemical(P-L)

Dry Deposition

Wet Deposition

Net Export

NOx 386 -337 44 ------ 5PANs   24 13 ------ 11∑ANs           ANs   18 7.4 3.6 7 R4N2   10 0.5 ------- 10HNO3   277 180 110 -3

Organic compounds may have much larger impact on global nitrogen cycling than previously thought!

Funded by NOAA CPO program, titled “Impact of organic nitrate chemistry on air quality and climate: past, present and future atmospheres” for 2013-2016.

Export of ∑ANs > Export of PANs

New chemistry

Previous studies without NOx recycling

Anthro NOx emissions in 2004

Reduce anthro NOx emissions of 2004 by 50%

Isoprene↑NOx ↓OH ↓O3 ↓ due to O3+ISOP

Surface ozone response to isoprene emissions:Implications for future air quality

NOx emissions↓

Sensitivity of ozone to isoprene emissions ↓

(Mao et al., submitted to JGR)

NOx emissions has been reduced by 34% from 2005 to 2011

OMI NO2 column in 2005 (summer)

OMI NO2 column in 2011 (summer)

difference

(Russell et al. 2012, ACP)

AM3 with updated chemistry

Updated chemistry Standard AM3 Observations

CASTNET sites

Improvement on ozone over SE US

(Naik et al., 2013, JGR, in press)

• Bias is reduced from 12.9 ppbv to 3.3 ppbv.• This should be reexamined by MDA8 ozone. Model tends to overestimate

monthly mean ozone.

Standard AM3 New chemistry in AM3

(C48 2001-2005)

Field studies over Southeast US in this summerSENEX (NOAA)

SOAS (NSF & EPA)NOMADSS (NCAR)

Two aircrafts based at Smyrna, TN and a tower located at Centerville, Alabama.

Measurements include VOC, NOx, ozone, aerosols, CCN etc.

GFDL will submit C180 nudge simulations to SENEX data archive.

A modeling workshop to be held in Rutgers U.

GFDL AM3 configuration for SENEX• Fully coupled chemistry-climate model

o Parameterizes aerosol activation into liquid cloud dropletso solves both tropospheric and stratospheric chemistry over the full domain

• Nudging wind with GFS meteorological field• High resolution (50 x 50 km) and coarse resolution (200 x 200 km)• MEGAN biogenic emissions (process-based emission)• Anthropogenic emissions use RCP 8.5 scenario (0.5 x 0.5 degree)• New heterogeneous chemistry (Mao et al., 2013a, ACP; 2013b, GRL)• New isoprene chemistry (Mao et al., submitted to JGR)

C48 (200 x 200km) C180 (50 x 50km)

Monthly mean ozone for July of 2012

Model of Emission of Gases and Aerosols from Nature (MEGAN)Process-based emission inventory

ageLAIPART

Temperature dependence Light dependence

Leaf age

6

1iiiE

Emission factor

Fractional coverage

Leaf Area Index

HCHO measurements in boundary layer for all flights in June

Monthly mean surface HCHO concentrations for June of 2012

Preliminary results from aircraft observations and AM3 C180 nudging simulation

One flight on June 03, 2013

Ozone (obs vs. model)

HCHO (obs vs. model)

Model does not show ozone bias.Model shows good agreement with HCHO.

Time Time

Flight altitude

1. Evaluate anthropogenic and biogenic emissions in AM3 over southeast US (aircraft, model and satellite).

2. Evaluate model simulation of ozone, SOA precursors from aircraft and ground measurements.

3. Implement a new module of in-cloud SOA processing from Liu et al. (2012).

4. Evaluate organic aerosol simulations (organic aerosols in particular) and its implications for future and past atmosphere.

The “role of aerosols in regional climate” was recently identified as an important crosscuttingresearch challenge for NOAA in the report “Toward Understanding and Predicting RegionalClimate Variations and Change”.

AM3 simulations on SENEX campaign

A new module of in-cloud SOA production developed in AM3 (Liu et al., 2012, JGR)

Question: What are the formation mechanisms of secondary species (ozone, sulfate and organics) in the SE U.S.?

We implemented a new set of chemistry in AM3, which significantly improves model simulation of ozone over SE US.

This updated chemistry show significant impact on global OH, CO, O3, nitrogen cycling, and have important implications on predicting future climate change and air quality.

GFDL is participating NOAA SENEX campaign with C180 nudging model.

Overestimate of ozone (puzzle 1) may be significantly improved from this study

Underestimate of organic aerosols (puzzle 2) can be at least partly improved in the model.

Conclusions

Sunrise

Entrainment zone

Model shows large amount of VOCs and OVOCs in the residual layer.

Is it possible to do a early morning flight to see the entrainment zone?

Boundary layer structure by Stull (1988).

Does nighttime chemistry affect global nitrogen/ozone budget?

Sunset

HCHO yield at different NOx conditions

Computed in a photochemical box model. Initialized with 1ppb isoprene.O3 (40ppb), CO (100ppb), and NOx are held constant.

Prompt HCHO formation, important for deriving isoprene emission from satellite observations.

Yield of HCHO is lower at lower NOx concentrations, according to the model.

But the model could be wrong!

SO4

NOxBVOCs

Current limitation: We have no constraints on these SOA precursors.

BC

OC

Aqueous reactions in cloud droplets

Direct uptake of organic compounds by aerosols

SOA precursors(Glyoxal, methyl glyoxal etc.)

SOA

Cloud evaporates

SOA

Two new pathways for SOA formation

O3

O2

O3

OH HO2

h, H2O

Deposition

NO

CH4, CO, VOCs

NO2

STRATOSPHERE

TROPOSPHERE

8-18 km

Tropospheric ozone chemistry

Air Quality

Climate

h

h

Annual average aerosol loading from IMPROVE site

Ammonium sulfate Organic aerosols

Surface measurements show low fraction of organic aerosols

NO3

ONO2

OO

NO3

ONO2

O

ONO2

O

OH

O2NO

O

R4N2

Nighttime chemistry

Based on Rollins et al. (2009) and Xie et al. (2012)

Nighttime yield of organic nitrates is 70%>> daytime yield (11.7%)

This chemistry was implemented in GEOS-Chem

Ozone in the boundary layer during ICARTT 2004Observations Model

Obs vs. ModelImproved O3-CO correlations due to:1. Recycling of NOx

from isoprene nitrates

2. HO2 uptake (lower OH and increase NOx lifetime).

(Mao et al., submitted to JGR)

Mean vertical profiles during ICARTT

O3 has no bias in boundary layer and free troposphere.HCHO provides good constraint on isoprene emissions.

ObservationsModel (GEOS-Chem)

(Mao et al., submitted to JGR)

Total organic nitrates excluding peroxyacylnitrates (∑ANs)

Model well reproduced ∑ANs.

∑ ANs is dominated by secondary organic nitrates(C3-C4).

∑ANs vs. HCHO ∑ANs vs. O3

Model well reproduced ∑ANs vs. HCHO and ∑ANs vs. O3 correlations.

These correlations cannot be reproduced by a fast isomerization channel of ISOPO2.

Vertical profiles Speciation of ∑ANs

SENEX 2013 field campaignSoutheast Nexus

Studying the Interactions Between Natural and Anthropogenic Emissions at the Nexus of Climate Change and Air Quality

Where: Southeast U.S.When: Summer 2013What: The focus of NOAA's field study includes GFDL modeling and ESRL CSD measurements using the NOAA WP-3D aircraft.Who: Investigators in this project include researchers from several universities, industries, and governmental agencies.

temperature, radiation, land use

Human activity

Air Quality

climate

ozone, aerosols

NOx

SO2

Isoprene emission to future climate and air quality

Biomass burning

isoprene emission

Lightning

NOx

CONH3

NOx

Isoprene oxidation process

Isoprene nitrates