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What can we learn about the Earth system using space-based observations of tropospheric chemical composition?
Paul Palmer, University of Leedswww.env.leeds.ac.uk/~pip
NO
HO2OH
NO2
O3hv
HC+OH HCHO + productsNOx, HC,
CO
Tropospheric O3 is an important climate forcing agent
IPCC, 2001
Level of Scientific Understanding
Natural VOC emissions (50% isoprene) ~ CH4 emissions.
Bottom-up Isoprene
emissions, July 1996
MEGAN
3.6 Tg C
GEIA
7.1 Tg C
[1012 atom C cm-2 s-
1]
Guenther et al, JGR, 1995
EPA BEIS2
2.6 Tg C
Pierce et al, JGR, 1998
Guenther et al, ACP, 2006
E = A ∏iγi
Emissions (x,y,t); fixed base emissions(x,y); sensitivity parameters(t)
Global Ozone Monitoring Experiment (GOME) &the Ozone Monitoring Instrument (OMI)
• GOME (European), OMI (Finnish/USA) are nadir SBUV instruments• Ground pixel (nadir): 320 x 40 km2 (GOME), 13 x 24 km2 (OMI)• 10.30 desc (GOME), 13.45 asc (OMI) cross-equator time • GOME: 3 viewing angles global coverage within 3 days• OMI: 60 across-track pixels daily global coverage• O3, NO2, BrO, OClO, SO2, HCHO, H2O, cloud properties
Launched in 2004
GOME HCHO columns
July 2001
[1016 molec cm-
2]
0 1 20.5
1.5
2.5
Biogenic emissions
Biomass burning
* Columns fitted: 337-356nm * Fitting uncertainty < continental signals
Data: c/o Chance et al
May
Jun Jul Aug
Sep
1996
1997
1998
1999
2000
2001
GOME HCHO column [1016 molec cm-2]
0 1 20.5
1.5
2.5
Palm
er
et
al, JG
R,
2006.
Tropospheric chemistry: a highly non-linear system, e.g. isoprene chemistry
Yield dependent on oxidant concentrations
•Models typically use a simplified (lumped) oxidation mechanism
•Assimilating HCHO possible but involves integrating many 100s of uncertain chemical reactions
•Neglected to mention other (more chemically uncertain) biogenic sources of HCHO!
•For now, we can extract lots of information from the HCHO using a simple method…
Relating HCHO Columns to VOC Emissions
VOC HCHOhours
OH
hours
h, OH
Local linear relationship between HCHO and E
kHCHO
EVOC = (kVOCYVOCHCHO)HCHO
___________
VOC source
Distance downwind
HCHO Isoprene
-pinenepropane
100 km
EVOC: HCHO from GEOS-CHEM CTM and MEGAN isoprene emission model
Palmer et al, JGR, 2003.
Net
Seasonal Variation of Y2001 Isoprene Emissions
•Good accord for seasonal variation, regional distribution of emissions (differences in hot spot locations – implications for O3 prod/loss).
•Other biogenic VOCs play a small role in GOME interpretation
May
Jun
Aug
Sep
Jul
0 3.5
7
1012 atom C cm-2s-
1
GOME MEGAN MEGAN GOME
Palmer et al, JGR, 2006.
GOME Isoprene Emissions: 1996-2001May Jun Jul Aug Sep
1996
1997
1998
1999
2000
2001
[1012 molecules cm-2s-1]0 5 10
Relatively inactive
Palm
er
et
al, JG
R,
2006.
Isop
ren
e fl
ux [
10
12 C
cm
-2 s
-1]
Julian Day, 2001
MEGANObsGOME
Sparse ground-truthing of GOME HCHO columns and derived isoprene flux estimates
Seasonal Variation: Comparison with eddy correlation isoprene flux measurements (B. Lamb) is encouraging
Atlanta, GA
May Jun July Aug Sep
PAMS Isoprene, 10-12LT [ppbC]
GO
ME H
CH
O [
10
16 m
ole
c c
m-2]
1996 1997 1998 1999 2000 2001Interannual Variation:
Correlate with EPA isoprene surface concentration data. Outliers due to local emissions.
Atlanta, GA
PROPHET Forest Site, MI
Surface temperature explains 80% of GOME-observed variation in HCHO
NCEP Surface Temperature [K]
GO
ME H
CH
O S
lant
Colu
mn
[10
16 m
ole
c cm
-2]
G98 fitted to GOME data
G98 Modeled curves
Time to revise model parameterizations of isoprene emissions?
Palm
er
et
al, JG
R,
2006.
Tropical ecosystems represent 75% of biogenic NMVOC emissions
1996
1997
1998
1999
2000
2001
What controls the variability of NMVOC emissions in tropical ecosystems?
Importance of VOC emissions in C budget?
Kesselmeier, et al, 2002
GOME HCHO column, July
Challenges: Cloud cover, biomass burning, and lack of fundamental understanding of NMVOC emissions…
em
issio
n r
ate
(C
)(µ
g g
-1 h
-1)
PA
R(µ
mol m
-2 s
-1)
assim
ilati
on
(C
)(m
g g
-1 h
-1) 0
123456
limonene myrcene b-pinene a-pinene sabinene
500
1000
1500
00:0006:0012:00
18:0000:00
06:0012:00
18:0000:00
0
2
4
local time [hh:mm]
10
20
30
40
tem
pera
ture
[°C
]
0
2
4
G93
for
isop
.[s
um
of
mon
ote
rpen
es]
tran
sp
irati
on
(mm
ol m
-2 s
-1)
monoterpene emission of Apeiba tibourbou
OMI, 24/9-19/10, 2004
13x24 km2
TES data @ 6km, 11/04
O3
CO
MODIS Firecount
O3-CO-NO2-HCHO-firecount correlations import to utilize when looking at the tropics
Improved cloud-clearing algorithms and better spatial resolution data help.
TES data c/o Bowman, JPL
A more integrated approach to understanding controls of NMVOCs, e.g., surface data, lab data,
Africa
Some aerosol-climate effects
South America Africa
Fe fertilization
deposition
Primary and secondary
aerosol sources: biomass burning,
biogenic, desert dust
Internally or externally mixed?
visibility
CCN
D Z
N POcean Ecosystem
SEVERI AOD
40
45
50
55
60
65
70
- 60 - 50 - 40 - 30 - 20 - 10 0 10
“Normal” airmass flow
44
46
48
50
52
54
56
- 20 - 15 - 10 - 5 0 5 10
Stagnant airmass flow
0
200
400
600
800
1000
1200
1400
27-Jul
29-Jul
31-Jul
2-Aug
4-Aug
6-Aug
8-Aug
10-Aug
12-Aug
14-Aug
16-Aug
18-Aug
20-Aug
22-Aug
24-Aug
26-Aug
28-Aug
30-Aug
0
5
10
15
20
25
30
35
40
Tem
pera
ture
(C
)
Isop
ren
e (
pp
t)
Estimated up to 700 extra deaths attributable to air pollution (O3 and PM10) in UK during this period
O3 > 100 ppb on 6 consecutive days
2pm, 6th Aug, 2003
Compiled from UK ozone network data
Isoprene c/o Ally Lewis
“Expect harmful levels of ozone and PM2.5 over the next couple of days; please keep small children and animals inside. Transatlantic pollution represents 20% of today’s UK surface ozone.”
2010
Resolution of new satellite data allows study UK AQ from space
SCIA NO2 @ 0.4x0.4o, Aug 2004
GOME NO2 @ 1x1o
Aug 1997
NAEI NOX emissions as NO2, 2002
GOME and SCIA NO2 c/o R. Martin; OMI (unofficial) NO2 c/o
T. Kurosu
Length
of
day
[hours
]
Day of Year
Edinburgh, 56N
Denver, 40N Cloud cover [%], ISCCP August 83-04
30 10070
OMI NO2 @ 0.1ox0.1o, Jul 2004
The increasing role of BVOCs: constraints from OMI HCHO?
Stewart et al, 2003Isoprene
MonoterpenesBVOC fluxes for a “hot, sunny” day
1016 [molec cm-
2]
OMI HCHO
2<0.3
• Unclear what PM characteristics affect health
• Secondary PM is formed from:– Oxidation of organic
compounds
– Oxidation of SO2
– Difficult to estimate offline – need models and data
MISRSurface PM2.5 =
ModelSurface [PM2.5] x MISR AOT
Model AOT2003
roadside (primary)
PM10
MISR AOT can help estimate total PM2.5:
Space-based aerosol optical properties can help map emissions of particulate matter
Liu
et
al,
2004
Case study of Oregon Fire using data from the Multi-angle Imaging SpectroRadiometer (MISR)
1
2
3
4
5
0.0 0.6 1.2 0.0 1.2 2.4 0 5000 10,0001
2
3
4
5
Kahn, et al., JGR, submitted
Plume Periphery: Higher AOT, Lower ANG, Lower SSA than BackgroundPlume Core: Too Thick & Variable for Standard AOT Retrieval
How do we optimally use this information operationally?
Current Development in Modelling UK AQ
• UK currently using MODELS 3 (MM5 + CMAQ) for AQ
1) UM mesoscale CTM
UKMO Unified Model
2) UKCA gas-aerosol chemistry scheme
AQ-climate links
AQ Model Chem-Clim Model
•Similar equations for data assimilation and inverse modelling
J(x) = ½(yo – H(x))T(E+F)-1(yo-H(x)) +½(x-xb)TB-1(x-xb)
•Multi-species analyses – inter-species error covariance?•Radiance versus retrieved products?•Limit of linearization of non-linear oxidant chemistry?
Global vs urban chemistry? Subgrid scale processes?
“First global space-based measurements of CO2 with the precision and spatial resolution needed to quantify carbon sources and sinks”
The Orbiting Carbon Observatory (OCO)
• Spectroscopic observations of CO2 (1.61 m and 2.06 m) and O2 (0.765 m) to estimate the column integrated CO2 dry air mole fraction,
XCO2 = 0.2095 x (column CO2) / (column O2)• Precisions of 1 ppm on regional scales • Global coverage in 16 days (nadir 1x1.5 km footprint)• JPL-based instrument: PI D. Crisp; Deputy PI: C. Miller (Crisp et al, 2004)
Launch in 2008
2-year mission