atmospheric methane distribution, trend, and linkage with surface ozone
DESCRIPTION
X. 10.40. 10.23. Change in mean ( t ) from 90-95 to 00-04 (years). +. =. 547. 548. 557. Recycled NCEP 1990-2004. D T(+0.3K). D OH(+1.4%). BASE. ANTH+BIO best captures measured abundances. 1990. 1995. 2000. Change in summertime U.S. afternoon surface O 3. 80 60 40 20 0. - PowerPoint PPT PresentationTRANSCRIPT
Atmospheric Methane Distribution, Trend, and Linkage with Surface OzoneArlene M. Fiore1 ([email protected]), Larry W. Horowitz1, Ed Dlugokencky2, J. Jason West3
1NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ 2NOAA Global Monitoring Division, Earth System Research Laboratory, Boulder, CO 3Atmospheric and Oceanic Sciences Program and Woodrow Wilson School, Princeton University, Princeton, NJ
1. Introduction
REFERENCESDentener, F., et al. (2003), J. Geophys. Res., 108, 4442, doi:10.1029/2002JD002916. Dlugokencky, E.J., et al. (2003), Geophys. Res. Lett., 30, 1992, doi:10.1029/2003GL018126. Dlugokencky, E.J., et al. (2005), J. Geophys. Res., 110, D18306, doi:10.1029/2005JD006035. Horowitz, L.W., et al. (2003), J. Geophys. Res., 108, 4784, doi:10.1029/2002JD002853.
What is driving observed CH4 trends? Does CH4 source location influence the O3 response?
• Methane (CH4) emission controls can be a cost-effective strategy for abating both global surface ozone (O3) and greenhouse warming [West and Fiore, 2005; see also poster by West et al.]
previous modeling studies used fixed CH4 concentrations and globally uniform changes, but CH4 is observed to vary spatially and temporally
• The major sink of CH4 is reaction with tropospheric OH; emissions of CH4 are shown in Section 2
• Surface CH4 rose by ~5-6 ppb yr-1 from 1990-1999, then leveled off (Section 3), possibly reflecting: (1) source changes of CH4 [e.g. Langenfelds et al., 2002; Wang et al., 2004] or other species that influence OH [e.g. Karlsdóttir and Isaksen, 2000] (2) meteorologically-driven changes in the CH4 sink [e.g. Warwick et al., 2002; Dentener et al., 2003; Wang et al., 2004] (3) an approach to steady-state with constant lifetime [Dlugokencky et al., 2003]
• Ozone response is largely independent of CH4 source location
• 30% decrease in global anthropogenic CH4 emissions reduces JJA
U.S. surface afternoon O3 by 1-4 ppbv
• BASE simulation (constant emissions) captures observed rate of
CH4 increase from 1990-1997, and leveling off post-1998
• ANTH emissions improve modeled CH4 post-1998
• Wetland emissions in ANTH+BIO best match the observed CH4
seasonality, interhemispheric gradient, and global mean trend
• CH4 decreases by ~2% from 91-95 to 00-04 due to warmer
temperatures (35%) and higher OH (65%, resulting from a ~10% increase in lightning NOx emissions)
Future research should:• consider climate-driven feedbacks from fire and biogenic emissions on
CH4
• develop more physically-based parameterizations of lightning NOx emissions to
determine whether higher emissions are a robust feature of a warmer climate
Van Aardenne, J.A., F. Dentener, J.G.J. Olivier and J.A.H.W. Peters (2005), The EDGAR 3.2 Fast Track 2000 dataset (32FT2000).Wang , J.S., et al. (2004), Global Biogeochem. Cycles, 18, GB3011, doi:10.1029/2003GB002180. Warwick, N.J., et al. (2002), Geophys. Res. Lett., 29 (20), 1947, doi:10.1029/2002GL015282 West, J.J. and A.M. Fiore (2005), Environ. Sci. & Technol., 39, 4685-4691.
Karlsdóttir, S., and I.S.A. Isaksen (2000), Geophys. Res. Lett., 27 (1), 93-96. Langenfelds, R.L., et al. (2002), Global Biogeochem. Cycles, 16, 1048, doi:10.1029/2001GB001466.Olivier, J.G.J., et al. (1999), Environmental Science & Policy, 2, 241-264.Olivier, J.G.J. (2002) In: "CO2 emissions from fuel combustion 1971-2000", 2002 Edition, pp. III.1-III.31. International Energy Agency (IEA), Paris. ISBN 92-64-09794-5.
3. Influence of Sources on Surface CH4 Distribution and Trend
1710
1720
1730
1740
1750
1760
1770
1780
1790
1990 1995 2000 2005
OBSERVED
BASE too low post-1998
ANTH improves CH4 vs. OBS post-1998
ANTH+BIO best captures measured abundances
Global mean surface CH4 concentrations as measured (or sampled in the model) at 42 Global Monitoring Division (GMD) stations [e.g. Dlugokencky et al., 2005] with an 8-year minimum record. Values are area-weighted after averaging in latitudinal bands (60-90N, 30-60N, 0-30N, 0-30S, 30-90S).
Mean model bias and correlation with 1990-2004 monthly mean surface GMD observations
BASEANTHANTH+BIO
-90 -50 0 50 90Latitude
100
50
0
-50
-100
Bia
s (p
pb
)r2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
BASE wetlandemissions yield a closer match with observedCH4 in tropics
nm
ol/
mo
l =
pp
b i
n d
ry a
ir
2. Methane in the MOZART-2 CTM
BASEConstant emissions (1990)
Sensitivity simulations applying different CH4 emission inventories:
ANTH Time-varying anthropogenic emissions
ANTH + BIO Time-varying anthropogenic and wetland emissions
EDGAR v3.2 1990,1995 and “FAST-TRACK” 2000 anthrop. emissions [Olivier, 2002; van Aardenne et al., 2005]
Biogenic source adjusted to match BASE 1990 total
200
210
220
230
240
250
260
270
1990 1995 2000 2005
Tg
CH
4 yr
-1
Apply climatological mean post-1998, scaled to equal biogenic total in ANTH (224 Tg yr-1)
From Wang et al. [2004]
6. Conclusions
OBS (GMD) BASE ANTH ANTH+BIO
ANTH+BIO improves:(1) High N latitude seasonal cycle, (2) Trend, (3) Low bias at S Pole, especially post-1998
1900
1850
1800
184018201800178017601740
1800
1750
1700
1740
1720
1700
1680
1660
1640
1990 1995 2000 2005
Alert (82.4N,62.5W)
South Pole (89.9S,24.8W)
Mahe Island (4.7S,55.2E)
Midway (28.2N,177.4W)
Surface CH4 concentrations at selected GMD stationsn
mo
l/m
ol
= p
pb
in
dry
air
Tropospheric O3 response toanthropogenic CH4 emission
changes is approximately linear
5. Ozone Response to CH4 Emission Controls
Stronger sensitivity in NOx-saturated regions (Los Angeles), partially due to local O3 production from CH4
O3 change independent of CH4 source location except for <10% effects in the Asian source region
Latitudinal distribution of 1990 CH4 emissions for cases shown below
BASEANTHANTH+BIO
-90 -50 0 50 90
Latitude
80
60
40
20
0
Tg
CH
4 yr
-1
4. Meteorologically-driven Changes in the CH4 Lifetime
Meteorological drivers for trend Not just an approach to steady-state
Global mean surface CH4 in BASE simulation (constant emissions)
1740
1750
1760
1770
1780
1790
1800
1810
1990 1995 2000 2005 2010 2015 2020
Recycled NCEP 1990-2004
CH4 Lifetime Against Tropospheric OH
Mean annual CH4 lifetime shortens
9.9
10
10.1
10.2
10.3
10.4
10.5
1990 1995 2000 2005
10.4010.23
Deconstruct from 91-95 to 00-04 into individual contributions by varying T and OH
separately
OH increases in the model by +1.4% due to a 0.3 Tg N yr-1 increase in lightning NOx
ANTH+BIO bestcaptures the CH4
interhemisphericgradient
ANTH+BIO improves the correlation withwith observationsat high northernlatitudes
547
Tg
CH
4 yr
-1
Biogenic andbiomass burning fromHorowitz et al. [2003]
Anthropogenic(energy, rice, ruminants)from EDGAR 2.0[Olivier et al., 1999]
Ch
an
ge in
mean
()
fro
m90-9
5 t
o 0
0-0
4 (
years
)
+ =
BASET(+0.3K) OH(+1.4%)
• ~100 gas and aerosol species, ~200 reactions• NCEP meteorology 1990-2004• 1.9o latitude x 1.9o longitude x 64 vertical levels• detailed description in Horowitz et al. [2003]
Change in summertime U.S. afternoon surface O3
MEAN DIFFERENCE MAX DAILY DIFFERENCE
ZERO ASIAN ANTHROP. CH4
GLOBAL 30% DECREASE IN ANTHROP. CH4
ppbv
Simulations of anthropogenic CH4 emission reductions (relative to BASE)
trop
osp
heric O
3 (Tg
)
Year
su
rfac
e C
H4
(pp
b)
Change in CH4 and O3 approaching
steady-state after 30 years
BASE captures observed rate of increase 1990-97and leveling off after 1998
547 548 557
Tg
CH
4 yr
-1
1990 1995 2000
MOZART-2 (this work)TM3 [Dentener et al., ACPD, 2005]GISS [Shindell et al., GRL, 2005GEOS-CHEM [Fiore et al., GRL, 2002]IPCC TAR [Prather et al., 2001]
X
-400
-350
-300
-250
-200
-150
-100
-50
0
1 6 11 16 21 26 31
-12
-10
-8
-6
-4
-2
0
0 4 9 13 17 21 29