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![Page 1: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/1.jpg)
Using space-borne measurements of HCHO to test
current understanding of tropical BVOC emissions
Paul Palmer University of Edinburgh
xweb.geos.ed.ac.uk/~ppalmer
![Page 2: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/2.jpg)
Current model estimates show that tropical ecosystems represent 75% of global biogenic
NMVOC emissions
Guenth
er
et
al,
200
7
But how accurate are these estimates? How well do we understand observed surface flux variability?
![Page 3: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/3.jpg)
Barkley et al, in prep., 2007
Because measurements are sparse including individual data points (and extrapolating them to plant functional
types) have a big effect on bottom-up models
![Page 4: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/4.jpg)
Pfister et al, in review, 2007
From CH4
From isoprene
From other
Contribution of isoprene to Amazon chemical budget
NCAR MOZART-4 CTM
MODIS #1CL
MMODIS
#2
LAI/PFT maps
![Page 5: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/5.jpg)
An integrative perspective is required
Net canopy VOC flux
Con
cen
trati
on
(z)
Column abundance
d[HCHO]/dt = [VOC][OH]k – [HCHO][OH]k’
In-canopy sinks
![Page 6: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/6.jpg)
GOME HCHO columns: July 1998
[1016 molec cm-
2]
Biogenic emissionsPalmer et al, Abbot et al, Millet et al
Biomass burning*Columns fitted: 337-356nm
*Pixel: 320km x 40km * Fit uncertainty < continental signals * Only use cloud fraction<40%
Data
: c/o C
hance
et
al
South Atlantic Anomaly
Fu et al, Shim et
al
Curci et al
Palmer et al, Barkley
et al
![Page 7: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/7.jpg)
Monthly mean AVHRR LAIMEGAN (isoprene)
Canopy model; Leaf age; LAI; Temperature; Fixed Base factors
GEIAMonoterpenes; MBO;Acetone; Methanol
MODEL BIOSPHERE
GEOS-Chem chemistry transport model
Chemistry and transport run at 2x2.5 degrees ANDsampled at GOME scenes
PAR, T
Emissions
Parameterized HCHO source from monoterpenes and MBO using the Master Chemical Mechanism
d[HCHO]/dt = [VOC][OH]k –[HCHO][OH]k’
GFED biomass burning
emissions
![Page 8: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/8.jpg)
Master Chemical Mechanism yield calculations
Cu
mu
lati
ve H
CH
O y
ield
[p
er
C]
0 2 4 6 8 10 12 14 16 18 20 220.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
HC
HO
YIE
LD
PE
R C
RE
AC
TE
D
DAYS
NOX= 1 PPB NOX= 100 PPT
pinene
( pinene similar)DAYS
0.4
0 20 40 60 80 100 120 1400.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55C
umm
ula
tive
HC
HO
Yie
ld fr
om
iso
pren
e o
xid
atio
n (p
er C
)
TIME (HOURS)
NOX = 0.1 PPB
NOX =1 PPB
Figure 18. Formation of HCHO from isoprene. Vertical lines denote midnight of each day
Isoprene
HOURS
0.5NOx = 1 ppb
NOx = 0.1 ppb
Parameterization (1ST-order decay) of HCHO production from monoterpenes in global 3-D CTM – MAX 5-10% of column
Higher CH3COCH3 yield from monoterpene oxidation delayed (and smeared) HCHO production
Palmer et al, JGR, 2006.
C5H8+OH(i) RO2+NOHCHO, MVK, MACR
(ii) RO2+HO2ROOH
ROOH recycle RO and RO2
![Page 9: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/9.jpg)
Month
ly
ATSR
Fire
counts
Sla
nt
Colu
mn
HC
HO
[1
016 m
ole
c cm
-2]
Day of Year
Significant pyrogenic HCHO source over South America
Good: Additional trace gas measurement of biomass
burning; effect can beidentified largely by
firecounts.
Bad: Observed HCHO is a mixture of
biogenic and pyrogenic – difficult to
separate without better temporal and
spatial resolution
ATSR Firecount
![Page 10: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/10.jpg)
Remove HCHO if concurrent NO2 > 8x1015 molec/cm2
Barkley et al, in prep., 2007
Firecounts and GOME NO2 columns are used to remove pyrogenic HCHO signal over western South America
NO2 HCHO
10
15,
10
16
[mole
c/cm
2]
HCHO NO2
![Page 11: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/11.jpg)
Model HCHO columns are typically 20% higher than GOME data
Model and observed
columns are better
correlated in the dry season
![Page 12: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/12.jpg)
Ground-based and aircraft measurements of isoprene and/or HCHO are sparse but invaluable for evaluating
satellite dataTrostdorf et al, ACPD, 2007
Helmig et al, JGR, 1998
Kuhn et al, JGR, 2002
Kuhn et al, ACP, 2007
![Page 13: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/13.jpg)
Kuhn et al, ACP, 2007
Barkley et al, in prep, 2007.
Helmig et al, JGR, 1998 MEGAN 2004
Ts
MEGAN 2004 T(1)
MEGAN 2006
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Annual cycle of isoprene
Hypothesis: water availability has a role in determining the magnitude of isoprene emission in the dry season
In situ isoprene 2002
Tro
stdorf e
t al,
200
4
Isop
ren
e [
pp
b] Dry season
Trostdorf et al, ACPD, 2007
![Page 15: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/15.jpg)
Carswell, et al, 2002 Huete et al, 2006
In situ isoprene 2002
Tro
stdorf e
t al,
20
04
Isopre
ne [
ppb]
Dry seasonLA
I
1999
Vegetation seasonal phenology (mean +/- sd). Satellite EVI and local tower GPP at Tapajos primary forest (km 67 site, 2002-2004).
Other factors affecting phenology?
Kuhn e
t al, 2
00
4
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Dry season
Barkley et al, in prep, 2007.
GEOS-Chem(MEGAN) has only a weak annual cycle compared with data, symptomatic of model
deficiency
Bias = +102%; r2 = 0
Bias = +38%; r2 = -0.2
Bias = +180%; r2 = 0
![Page 17: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/17.jpg)
Kuhn et al, JGR, 2002
Are bottom-up inventories biased towards dry season measurements?
GEOS-Chem over estimates surface [HCHO] during (1) the wet season and (2) night time
Model does NOT account for in-canopy chemistry and not a fair data comparison
![Page 18: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/18.jpg)
HCHO Columns Over NW South America
Use GOME NO2 and ATSR firecounts to remove pyrogenic HCHO S
lan
t C
olu
mn H
CH
O [
10
16 m
ole
c cm
-2]
Month
2.5
2.0
1.5
1.0
0.5
0.0
Q: What’s driving this seasonal distribution of HCHO?
In situ isoprene 2002
Tro
stdorf e
t al,
20
04
Isopre
ne [
ppb]
Dry season
![Page 19: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/19.jpg)
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
![Page 20: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/20.jpg)
LL-VOC ELL-VOC + SL-VOCESL VOC = HCHO
kHCHO
(kVOCYVOCHCHO)___________ =
Background due to CH4, CH3OH
, GEOS-Chem chemistry mechanism
Isoprene emission E [1013 atomC cm-2 s-1]
May
AugJul
Jun
r = 0.9
r = 0.9
r = 0.8
r = 0.9
Mod
el
HC
HO
[10
16 m
ole
c cm
-2]
Slope = 2000-2200 s
Intercept (background) = 5-6x1015 molec/cm2
![Page 21: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/21.jpg)
Isoprene emissions [1013 molec/cm3/s]
MEGAN GOME
Apr
Jun
Aug
Oct
MODIS EVI
![Page 22: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/22.jpg)
Bottom-up emission inventories typically represent within-canopy measurements:(1) Within-canopy turbulence and chemistry are sub-grid scale processes in global 3-D CTMs (2) Artificially increase [OH] to remove isoprene faster would be problematic in global CTMs
Con
cen
trati
on
(z)
Net canopy VOC flux
Column abundance
d[HCHO]/dt = [VOC][OH]k – [HCHO][OH]k’
In-canopy sinks
Provided GEOS-CHEM d[HCHO]/dt
is correct then canopy fluxes of VOCs inferred
from HCHO columns are more suitable for global
models
![Page 23: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/23.jpg)
What we’ve shown….
Satellite observations of HCHO have strong (and distinct) pyrogenic and biogenic signatures.
GOME HCHO data are broadly consistent with the temporal variability observed by ground-based data, particularly the partitioning between wet and dry season.
GOME HCHO data are qualitatively consistent with bottom-up isoprene emissions in the dry season (when model bias is greatest).
Bottom-up models (here, we pick on MEGAN!) lack data to provide robust isoprene estimates over South America.
Isoprene emissions inferred from GOME represent the canopy-atmosphere flux – what global 3-D CTMs want.
![Page 24: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/24.jpg)
Open questions that still need to be answered…
How do we reconcile the apparent discrepancy between ground-based measurements of isoprene flux and concentration and oxidation products?
Are GOME isoprene fluxes more consistent with ground-based data? [Calculations running as we speak]
Why are isoprene fluxes in the dry season higher than in the wet season? Light vs drought: are GOME isoprene fluxes more consistent with seasonal changes in EVI or drought indices?]
How important is isoprene to the regional carbon budget?
Will better spatial and temporal resolved satellite data improve estimates?
![Page 25: Using space-borne measurements of HCHO to test current understanding of tropical BVOC emissions Paul Palmer University of Edinburgh xweb.geos.ed.ac.uk/~ppalmer.](https://reader030.fdocuments.us/reader030/viewer/2022032707/56649e0f5503460f94af9f4f/html5/thumbnails/25.jpg)
SPARE SLIDES
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Vertical column retrievals
8 x 1016 molec cm-2T
ransm
issi
on
Chance et al, GRL, 2000
337-356 nm (O3, NO2, BrO, O2-O2)
1) Direct fit of observed radiances: slant columns
AMF = AMFG w() S() d1
0
Radiative transfer
Normalised HCHO profile
Palmer et al, JGR, 2001
2) Air-mass factor calculation: vertical columns
Estimated Error Budget
Slant column fitting: 4x1015 molec cm-2
AMF:
1) UV albedo (8%)
2) Model error (10%)
3) Clouds (20%)
4) Aerosols (20%)
Subtotal 30%
For a vertical column of 2x1016 molec cm-2 and AMF of 0.7
TOTAL = 9x1015 molec cm-2
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Month of 2000
50
0
Mod
el b
ias
[%]