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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.

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two puzzles of atmospheric chemistry over the southeast us

Two puzzles of atmospheric chemistry over the Southeast US

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

Funding from NOAA CPO

slide2

What is so unique for Southeast US?

Anthropogenic + Natural

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

Surface NOx is mainly produced from anthropogenic activities

(Martin et al., 2008, AE)

(Millet et al., 2008, JGR)

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

Importance of NOx

  • sources of organic aerosol
  • sources/sinks of oxidants (ozone, OH)

Increasing functionality & cleavage

h

O3

OH + products

NO2

h

OH

R’O2

carbonyls

NO

organic aerosol

OH

VOC

RO2

HO2

organic

peroxy

radicals

OH,h

ROOH

products

organic

peroxides

biosphere

combustion

industry

OVOCs

deposition

EARTH SURFACE

global budget of organic aerosols
Global Budget of Organic Aerosols

Global sources in Tg C y-1

20

K

OH, O3,NO3

SOG

SOA

VOC

Two-product

?

POA

Aqueous reactions

isoprene

terpenes

oxygenates…

?

50

Uptake on

cloud droplets

or aerosols

20

100

700

alkenes

aromatics

oxygenates…

30

vegetation fuel/industry open fires

fuel/industry open fires

VOC EMISSION

PRIMARY EMISSION

SOA ≡ secondary organic aerosol

POA ≡ primary organic aerosol

Current AM3 treats SOA production as yield of terpene emissions.

summertime ozone over eastern us is a problem for most models
Summertime ozone over eastern US is a problem for most models

Northeast US

Standard AM3

Multimodel mean

Obs from CASTNET surface sites

Southeast US

Multimodel mean

Obs from CASTNET surface sites

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

(Fiore et al., 2009, JGR)

slide7

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)

slide9

Temperature trend over past century

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

1930-1990 change in

Annual Mean Surface Temperature

(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).

(Portmannet al., 2009, PNAS)

slide10

The cooling can be partially due to secondary organic aerosols

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.

(Goldstein et al., PNAS, 2009)

slide11

Similar problem was found in GFDL models

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

CM 2.1

CM 3

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

(Courtesy of Paul Ginoux and Ilissa Ocko)

surface air temperature

Surface Air Temperature

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

OBS (GISS)

CM2.1

CM3

K

(Courtesy of Larry Horowitz)

Stronger cooling at northern mid-latitudes in CM3,

3x less warming globally  examine forcings

slide13

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.

slide14

New development of chemistry in AM3:

(1) heterogeneous chemistry

slide15

A new framework for heterogeneous chemistry

Standard AM3

N2O5, HO2

SO4

Hygroscopic growth factor

Updated AM3

N2O5, HO2, NO3, NO2

SO4

OC

BC

dust

SeaSalt

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

slide16

Impact of heterogeneous chemistry (AM3 C48 2001-2005)

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

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

slide17

Improvement on CO at 500 hPa

Improvement on OH ratio (NH/SH)

MOPITT

AM3 with het chem off

obs

AM3 with het

chem on

(Naiket al., 2013, JGR, in press)

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

slide18

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)

slide19

Aerosol uptake has large impact on ozone production efficiency

Observations

ΔO3/ΔCO is a measure of ozone production efficiency.

slide20

Sensitivity of tropospheric oxidants to biomass burning emissions

Global OH decreases with larger bb emissions.

Global ozone increases with larger bb emissions.

slide21

Nonlinearity of total radiative forcing on biomass burning strength

Chemical indirect forcing from CH4and CH4-induced changes in O3 and stratospheric

H2O, is comparable to the cooling from biomass burning aerosols

with direct and indirect effect taken into account.

Steady state CH4

CH4-induced O3 and H2O

How about chemical indirect forcing from anthropogenic emissions?

(Mao et al., 2013b, GRL)

slide22

New development of chemistry in AM3:

(2) a new isoprene chemistry scheme

slide23

A new isoprene oxidation mechanism for global models

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

(Mao et al., submitted to JGR)

slide24

Was OH really that high over SE US during ICARTT?

A new method of measuring OH was deployed in Blodgett Forest

OH measured by traditional method during ICARTT 2004

(Ren et al., 2008, JGR)

(Mao et al., 2012, ACP)

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

slide25

First generation of isoprene nitrates degraded to second generation nitrates!

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.

Second generation isoprene nitrates (C3-C4)

(Paulot et al., 2009a,b)

slide26

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

Export of ∑ANs > Export of PANs

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.

slide27

Surface ozone response to isoprene emissions:

Implications for future air quality

NOx emissions↓

Sensitivity of ozone to isoprene emissions ↓

New chemistry

Isoprene↑

NOx ↓

OH ↓

O3 ↓ due to O3+ISOP

Previous studies without NOx recycling

AnthroNOx emissions in 2004

Reduce anthroNOx emissions of 2004 by 50%

(Mao et al., submitted to JGR)

slide28

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)

slide30

Updated chemistry Standard AM3 Observations

CASTNET sites

slide31

Improvement on ozone over SE US

Standard AM3

New chemistry in AM3

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

(C48 2001-2005)

  • 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.
slide32

Field studies over Southeast US in this summer

SENEX (NOAA)

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.

NOMADSS (NCAR)

SOAS (NSF & EPA)

gfdl am3 configuration for senex
GFDL AM3 configuration for SENEX
  • Fully coupled chemistry-climate model
    • Parameterizes aerosol activation into liquid cloud droplets
    • 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)

C180 (50 x 50km)

C48 (200 x 200km)

Monthly mean ozone for July of 2012

slide34

Model of Emission of Gases and Aerosols from Nature (MEGAN)

  • Process-based emission inventory

Leaf age

Leaf Area Index

Temperature dependence

Light dependence

Fractional coverage

Emission factor

slide35

Preliminary results from aircraft observations and AM3 C180 nudging simulation

HCHO measurements in boundary layer

for all flights in June

Monthly mean surface HCHO concentrations for June of 2012

slide36

Model does not show ozone bias.

Model shows good agreement with HCHO.

One flight on June 03, 2013

Flight altitude

HCHO (obs vs. model)

Ozone (obs vs. model)

Time

Time

slide37

AM3 simulations on SENEX campaign

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

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

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

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

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

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

The “role of aerosols in regional climate” was recently identified as an important crosscutting

research challenge for NOAA in the report “Toward Understanding and Predicting Regional

Climate Variations and Change”.

slide38

Conclusions

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.

slide39

Does nighttime chemistry affect

global nitrogen/ozone budget?

Sunset

Sunrise

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?

Entrainment zone

Boundary layer structure by Stull (1988).

slide40

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!

slide41

Two new pathways for SOA formation

Cloud evaporates

Aqueous reactions in cloud droplets

SOA

Direct uptake of organic compounds by aerosols

SO4

SOA precursors

(Glyoxal, methyl glyoxal etc.)

OC

SOA

BC

BVOCs

NOx

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

slide42

Tropospheric ozone chemistry

Air Quality

O2

hn

O3

STRATOSPHERE

Climate

8-18 km

TROPOSPHERE

hn

NO2

NO

O3

hn, H2O

OH

HO2

CH4,CO, VOCs

Deposition

slide43

Annual average aerosol loading from IMPROVE site

Ammonium sulfate

Organic aerosols

Surface measurements show low fraction of organic aerosols

slide45

Nighttime chemistry

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

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

slide46

This chemistry was implemented in GEOS-Chem

Ozone in the boundary layer during ICARTT 2004

Model

Observations

Obs vs. Model

Improved O3-CO correlations due to:

Recycling of NOx from isoprene nitrates

HO2 uptake (lower OH and increase NOx lifetime).

(Mao et al., submitted to JGR)

slide47

Observations

Model (GEOS-Chem)

Mean vertical profiles during ICARTT

O3 has no bias in boundary layer and free troposphere.

HCHO provides good constraint on isoprene emissions.

(Mao et al., submitted to JGR)

slide48

Total organic nitrates excluding peroxyacylnitrates (∑ANs)

Vertical profiles

Speciation of ∑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.

slide50

SENEX 2013 field campaign

Southeast Nexus

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

Where: Southeast U.S.

When: Summer 2013

What: 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.

slide52

Isoprene emission to future climate and air quality

Air Quality

isoprene emission

ozone, aerosols

temperature, radiation, land use

CO

NH3

NOx

NOxSO2

NOx

Biomass burning

Lightning

Human activity

climate