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Interannual variability and long-term trends in global tropospheric ozone and related chemistry during recent decades

*Kengo Sudo1,2

1Grad. School of Environmental Studies, Nagoya University, Nagoya, Japan2JAMSTEC, Yokohama, Japan

Quadrennial Ozone Symposium 2016

4–9 September 2016 Edinburgh, United Kingdom

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Emission/Formation of SLCFs (Short-lived Climate Forcers) and Climate Impacts

BCSulfate

Radiative forcing (ERF) for 1850-2005CHASER (MIROC-ESM)

Sudo et al. (2011)

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Interplay of Tropo./Strato. Chemistry and ClimateTropospheric chemistry is :1. influential in CH4 and aerosols: BC-aging, production of SO4

2--NO3--NH4

+, SOA2. tightly linked to Meteorological field (u,v,T,q,clouds,UV) as well as to emissions

Tropo.O3

OH

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Tropospheric Column O3 (Sep.2015‐, 3‐hourly)

CHASER (MIROC‐ESM)

(Dobson‐Unit)

Ozone and related chemistry are highly variable under the multiple influences of atmospheric chemistry & transport

EmissionsAnthropogenicBiomass BurningNatural

(LNOx, BVOCs, etc.)

Meteorology:TransportWater-vaporClouds

CHASER NAGOYA

To elucidate long-term trend and interannual variability (IAV) in O3 and related species (like OH) is a key to precise understanding of chemistry-climate interaction

This talk will discuss long-term trend and IAV in O3 and related species (OH, CH4) in recent decades using the CHASER simulations for CCMI project etc.

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CHASER-MIROC (MIROC-ESM-CHEM) Climate  Model Core  : MIROC‐4.5 (t42,L80) developed mainly in AORI/JAMSTEC/NIES/NU/KYU Chemistry :  CHASER‐V4 (Sudo et al., 2011)    ~250 reactions with >70 species

• Ox‐NOx‐HOx‐CH4‐CO chemistry  with VOCs (explicit C2s,C3s, and isoprene & terpene)• Halogen (ClOx/BrOx) chemistry with PSCs chemistry (Akiyoshi et al. 2004) nudged to HALOE• SO4

2‐ chemistry (SO2 oxidation with OH, O3/H2O2, cloud‐pH dependent)• SO4

2‐‐dust interaction• NO3

‐ and SOA (frm. Isoprene/Terpenes) chemistry Aerosol: SPRINTARS (Takemura et al., 2010)

• BC/OC, sea‐salt, and dust• BC aging with SOx/SOA production• Direct & indirect effects 

(incl. ice nuclei effects)

SLCFs Forcing :  O3(T/S), BC/OC, SO4, NO3, CH4

Wet Deposition:All calculated in CHASER

Natural emissions:  *BVOCs,LNOx,soil‐NOx/NH3, ocean‐NH3/VOCs, wet‐land‐CH4, DMS, etc.

*basically constant except for lightning NOx, & dust*Terpenes/Isoprene emissions= 120, 400 TgC/yr

Watanabe et al. (2011)

[H+]＋ [Ca2+]＋ [NH4+] =

[HCO3-] + [CO3

2-] + [NO3-] +

[SO42-] + [SO3

2-] + [HSO3- ] + [OH-]

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CCMI (Chem.‐Clim. Model Initiative) Experiments

GHGs ODS SST/IceStrato. aerosols Solar Precursor gases

REF-C1SD

Nudged to Era-I

Sensitvty simulations with impacts of changes in 1) Precursors emissions, 2) GHGs (Climatechange), 3) ODS, 4) Strato. Aerosols5) Solar

18 chemistry-climate models participate (Morgenstern et al., 2016)

For Meteorol. impacts during 2000-2015, emission-fixed simulation is also performed using the HTAP2 emission data (for 2008) and Era-Interim.

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1 (standard dev.) in annual mean surface concentrations for 1980-2014

O3 CO

run with interannually-constant emissons:Roles of Meteorological variability

ppbv

ppbv

ppbv

ppbv

Biomass Burning and meteorology as drivers of IAV and trend of O3 and CO

• In NH, O3.vs.COR=0.84

Biomass burning

Japan (regional mean O3)

Observed(AEROS)

Modelled (CHASER)

Nagashima et al. (2016)

For Japanese surface O3, long-term trend is determined by emission (mostly in China), with IAV by meteorol. Conditions.

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O3 IAV and trend:1980-2010

Long-term Trend 1.24 ppbv/d (1980-2010) is attributed mostly to emissions increases (1.08 ppbv/d) and partly to Met. Field (0.37 ppbv/d) as a result of large IAV

Trend after 2000 appears to be caused by Met.Field(&Strato.O3) rather than emissions

Fixed-emission simulation

trend

Global burden of tropospheric O3

Global NOx emission is kept constant after 2000(=HTAP2-2008)

?

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What controls IAV in tropo. column O3?

Regression coeff. (Nino 3.4 index) Due to Transport Due to Chemistry

= +

Impacts of ENSO cycles Sekiya & Sudo (2014)

Tropical eastern PacificDetrended-IAVIAV (CHASER v.s. TOMS-CCD)

IAV (CHASER v.s. TOMS-CCD) Detrended-IAV

Tropical western Pacific

Southern N-America

Northern Highlatitudes

Detrended-IAV

Detrended-IAV

IAV (CHASER v.s. O3-sonde)

IAV (CHASER v.s. O3-sonde)

ENSO component ENSO Hadley C.

AO

ENSO

ENSO IOD

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CCMI (Chem.‐Clim. Model Initiative) EXPsAnnual mean changes in O3 （19802010）

= +

Due to (emission)

Due to (meteorol. & strato. O3)Net change

Surface O3

Japan（April）：～+10ppbv

0.074 W m-264% 0.005 W m-20.069 W m-2

= +RF-O3

w m-2w m-2 w m-2

Surf. O3concentrations

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CCMI (Chem.‐Clim. Model Initiative) EXPsRadiative Forcing Changes （19602010）

w m-2 w m-2 w m-2

w m-2

0.30 W m-2 0.011 W m-2 -0.02 W m-2

-0.26 W m-2

RFs from aerosol and tropo. O3 changes are comparable in global mean

Climate change (GHGs) impacts on RF-O3 are regionally important, but very small in global mean

Likewise for stratospheric O3 change

Aerosol(net) direct

RF-O3due to Climate Change

RF-O3due to Emission

RF-O3due to Strat. O3 Change

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For 2000-2015, Non-emission factors (meteorol.&strato O3) appear to cause positive O3 trend in NH and tropics (except central to eastern Pacific)

OMI/MLS data (2005-2015) also show similar increase but with larger magnitude due to emission increase in Asia

Dobson Unit / dec

Recent trend (2000-2015) in tropo. O3

Linear trend (2000-2015) in tropo. Column O3

:2000-2014

Simulation with constant anthro. emissions (HTAP2-2008)

Simulation w.o. trend in anthro. emissions

1.33 ppbv/dec : WDCGG

1.60 ppbv/dec : CHASER

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Recent trend (2000-2015) in tropo. O3

Linear Trend (DU/decade)associated with Met./St.O3changes

CHASER run(fixed-Emissions=HTAP2008)

In general regions, observed O3trend is well explained by Met. and/or St. O3 changes

In E-Asia, emissions play a major role (ca. 6-9 ppbv/decade)

800-200hPa mean

~2ppbv/dec

~5ppbv/dec

~9ppbv/dec

~7ppbv/dec

~6ppbv/dec

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Global emission changes inferred with the CHASER data assimilation system

Data assim. with CHASER shows large increases of NOx emission in India and China during the last decade, which should have caused positive O3 trends in Asia (6-9ppbv/decade)

Miyazaki, Sudo, et al. (2016,ACP)

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Recent trend (2000-2015) in tropo. O3

Tropospheric O3 burden anomalies

Global

NH

SH

Net O3 trend

Simulation w.o. trend in anthro. emissions

Linear-trend (2000-2015) in zonal mean O3

Linear-trend (2000-2015) in zonal mean O3(St.)

ppbv

ppbv

Stratospheric O3

Net O

3

Pres

sure

/ hP

a

O3(St.) trend

STE increase?

H2O increase

Positive ozone trends appear to be caused by increase in STE

~+6 Tg(2000-2015)

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Trend in tropo. O3 and its budget (STE) In 2000‐2015, increasing STE (due to met. & strato. O3

changes) may be causing positive trend in tropo. O3. STE will continue to increase in future (aftr 2015) 

under every RCP scenario as suggested by many previ. studies (Sudo&Takahashi 2003, Zeng&Pyle 2003, Kawase et al., 2011, etc.)

For a long‐term perspective, warming trend and associated met. changes reduce tropospheric O3. 

Fixed-ODS (=1960s)

Ctrl (Net Forc.)

RCP6.0

Fixed-GHGs(=1960s)

GHGs effect (RCP6.0)

emission effect (RCP6.0)

ODS effects

Emergence of STE increase due to enhanced BDC and healing of strato.O3 ?

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OH trend for 2000-2015: impacts of Met. & Strato-O3.

O3*46%

J(1D)*12%

H2O*10%

LNOx*13%

CO*19%

CONTRIBUTION TO LINEAR OH TREND: 2000-2015

Zonal Mean OH trend: 2000-2015

(x105 molecules cm-3 / decade):

altit

ude

/ hPa

• OH has been increasing in the low latitudes (2-5%/decade)

• Increases in O3, H2O, J(O1D), LNOx, and decreases in CO are the principal factors.

• OH increase may have affected CH4 lifetime in combination with T increase (warming trend)

Simulation w.o. trend in anthro. emissions

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Long-term CH4 trend and its causes

-450

-350

-250

-150

-50

50

150

250

350

450

550

650

750

CH4 lifetime continues to decrease?

CH4 decrease due to Lifetime effects(fixed CH4 emiss=2000)

CH

4/ p

pbv

year

ΔCH

4/ p

pbv

CH4emission

Neteffect

GHGs

(CH4) effects

ODSsEmis:NOx,CO,VOCs

E(CH4)

What cause 1960-2010 CH4 change?

Global Mean CH4

Successful case !(increasing CH4emission after 2000)

CH4 trend after 2000

0

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Long‐term CH4 trend : 1960  2100

No climate changeFixed-Emission=1960(NOx,CO,VOCs)

Global Mean CH4

Ctrl (Net Forc.)

CH4 lifetime continues to decrease? After 2050, climate change, causing increases in OH and T, will play significant parts 

in future CH4 change (reduction) Before 2050, precursor emission (especially NOx) largely deters CH4 from increasing

Fixed-ODS

with RCP 6.0 emissions

year year

RCP6.0

GHGs effect (RCP6.0)

emission effect (RCP6.0)

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Summary & conclusions During the past few decades,

emission changes appear to be the dominant factor of long-term trend in trop.O3. IAV in surface O3 basically comes from biomass burning and partly from meteorological

variability, while free tropospheric O3’s IAV is nicely related to climate oscillation (ENSO, AO, Monsoon,

etc). Impacts of climate change on RF-O3 are regionally important, but negligible for global mean

RF.

For tropospheric O3 change during 2000-2015, emissions play major part in O3 increases in Asia, while in other regions, climate change & strato. O3 change appear to control O3 trend. Global O3 abundance is increasing during 2000-2015 in response to enhanced STE.

STE increase is going to continue in future due to enhanced BD circ. and strato O3 recovery.

Climate trend (warming) reduces tropospheric abundance in CH4 as well as O3 due to larger OH concentrations (in both the past and future) and higher temperature.

CH4 lifetime effect should be properly treated for SLCPs reduction strategy.

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O3 / CH4 as SLCPs and a warming mitigator

NOx emission reduction can lower O3’s heating but more enhance CH4’s

Net negative RF (cooling) is only expected in CO reduction cases.

‐1

‐0.5

0

0.5

1

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

グラフタイトル

O3 CH4 SO4 NO3BC OC Net

Rad

iativ

e fo

rcin

g re

lativ

e to

200

8 (W

m-2

)

2008 emission

↓

‐0.2

‐0.1

0

0.1

0.2

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

グラフタイトル

O3 CH4 SO4 NO3

BC OC Net

NOx emission changesE(HTAP2-2008) x 0 to 2

CO emission changesE(HTAP2-2008) x 0 to 2

(direct) Radiative forcing responses to:

For air quality, reduction in precursors (NOx,CO,VOCs) is favourable, however,