1. Ozone Monitoring Experiment
Using space-based measurements of formaldehyde to learn about BVOC distributions
Paul Palmer, University of Edinburgh
biogenic, pryogenic, anthropogenic
pryogenic
anthropogenic
biogenic
pyrogenic
Thomas Kurosu, Harvard-Smithsonian
HCHO August 2006
Ozone Monitoring Experiment

2. Tropospheric O3 is an important climate forcing agentNO
HO2 OH
NO2 O3 hv
HC+OH  HCHO + products
NOx, HC, CO
Level of Scientific Understanding
Natural VOC emissions (50% isoprene) ~ CH4 emissions.
IPCC, 2001

3. MEGAN Isoprene Emission Inventory
Environmental factors:
temperature
solar irradiance
leaf area index
leaf age
July
2003

4. Global Ozone Monitoring Experiment (GOME) & the Ozone Monitoring Instrument (OMI)
Launched in 2004
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), 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

5. HCHO Column Abundance Fitted in a Narrow UV Spectral Window
nm fitting window
Fitting uncertainty of slant columns is typically < 4x1015 molec cm-2

6. vertical column = slant column /AMF
GEOS-CHEM
satellite
lnIB/
Sigma coordinate ()
dHCHO 1
Earth Surface
HCHO mixing ratio C()
Scattering weights
Shape factor
S() = C() air/HCHO
w() = - 1/AMFG lnIB/ 1
AMF = AMFG  w() S() d

7. GOME HCHO columns July 2001 Biogenic emissions Biomass burning
– fractionally cloudy pixels (>40%) removed
Biogenic emissions
Biomass burning
July 2001
Data: c/o Chance et al
[1016 molec cm-2] 1 2
0.5
1.5
2.5
* Columns fitted: nm * Fitting uncertainty < continental signals

8. Relating HCHO Columns to VOC Emissions
hours OH
h, OH
VOC
Net
kHCHO
EVOC =
(kVOCYVOCHCHO)
HCHO
___________
Local linear relationship between HCHO and E
Three/four prong attack:
Chemistry; Emissions: magnitude and controls; Transport
VOC source
Distance downwind
WHCHO
Isoprene
a-pinene
propane
100 km
EVOC: HCHO from GEOS-CHEM CTM and MEGAN isoprene emission model
Palmer et al, JGR, 2003.

9. chemistry transport model
Modeling Overview
GEOS-CHEM global 3D
chemistry transport model
MCM: parameterized HCHO source from monoterpenes and MBO
PAR, T
Emissions
MODEL BIOSPHERE
MEGAN (isoprene)
Canopy model
Leaf age
LAI
Temperature
Fixed Base factors
GEIA
Monoterpenes
MBO
Acetone
Methanol
Monthly mean AVHRR LAI

10. MCM HCHO yield calculations
0.5
NOx = 1 ppb
NOx = 0.1 ppb
Isoprene
C5H8+OH(i) RO2+NOHCHO, MVK, MACR
(ii) RO2+HO2ROOH
ROOH recycle RO and RO2
Cumulative HCHO yield [per C]
HOURS
Higher CH3COCH3 yield from monoterpene oxidation  delayed (and smeared) HCHO production
0.4
Explain reasons for delayed production of HCHO from pinenes
Parameterization (1ST-order decay) of HCHO production from monoterpenes in global 3-D CTM
 pinene
( pinene similar)
DAYS
Palmer et al, JGR, 2006.

11. Seasonal Variation of Y2001 Isoprene Emissions
MEGAN
GOME
MEGAN
GOME
May
Jun
Aug
Sep
Jul
3.5 7
1012 atom C cm-2s-1
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
Palmer et al, JGR, 2006.

12. Isoprene flux [1012 C cm-2 s-1]
Sparse ground-truthing of GOME HCHO columns and derived isoprene flux estimates
Isoprene flux [1012 C cm-2 s-1]
Julian Day, 2001
MEGAN
Obs
GOME
May Jun July Aug Sep
Seasonal Variation: Comparison with eddy correlation isoprene flux measurements (B. Lamb) is encouraging
Atlanta, GA
PROPHET Forest Site, MI
Atlanta, GA
To evaluate the GOME interannual variability over the southeastern United
States we used isoprene concentration data from four EPA Photochemical
Assessment Monitoring Sites (PAMS, located
around Atlanta Georgia. Three of these sites are classed as surburban and one
is considered rural. Instantaneous concentration measurements are taken every
three hours using an automated GC with flame ionization detection. The
uncertainty of these individual measurements is 30\%
(Susan Zimmer-Dauphinee, EPA, personal communication, 2004).
Instruments are calibrated daily using an isoprene standard. Measurements that
do not agree with the standard to within a 30\% accuracy are discarded.
As with the HCHO columns, there
is a large degree of interannual variability in the observed seasonal
cycle on the continental scale (not shown).
\callout{Figure \ref{fig:pamsga}} shows that GOME HCHO column data captures
58\% of the temporal variability of the monthly mean isoprene concentrations
at all Atlanta sites, after removing one anomalous measurement (880~ppbC,
July 1996) and two outliers (June 1998 and August 1999). %
The value for the intercept (0.2$\times$10$^{16}$molec~cm$^{-2}$) in Figure
\ref{fig:pamsga},
corresponding to the HCHO column with no contribution from isoprene, is
half the background HCHO column that is expected from from CH$_4$ oxidation.
The two monthly mean outliers originate from the rural site that is sometimes
influenced by local biogenic emissions from the Kudzu vine, a known strong
emitter of isoprene (Susan Zimmer-Dauphinee, EPA, personal communication,
2004). The reason why these local biogenic emissions significantly influence
only a few months is unknown.
By comparing mean
summertime values (June$-$August) we effectively test the ability of GOME
to capture observed interannual variability in isoprene concentration. GOME
summertime columns between 1996$-$2001 capture 92\% of the observed
interannual variability.
GOME HCHO [1016 molec cm-2]
Interannual Variation: Correlate with EPA isoprene surface concentration data. Outliers due to local emissions.
PAMS Isoprene, 10-12LT [ppbC]

13. GOME Isoprene Emissions: 1996-2001
May
Jun
Jul
Aug
Sep
1996
1997
1998
1999
2000
2001
Palmer et al, JGR, 2006.
[1012 molecules cm-2s-1] 5 10

14. Surface temperature explains 80% of GOME-observed variation in HCHO
NCEP Surface Temperature [K]
GOME Isoprene Emissions [1012 atoms C cm-2s-1]
G98 fitted to GOME data
G98 Modeled curves
Palmer et al, JGR, 2006.
Time to revise model parameterizations of isoprene emissions?

15. Tropical ecosystems represent 75% of biogenic NMVOC emissions
What drives observed variability of tropical BVOC emissions?

16. Significant pyrogenic HCHO source over tropics Monthly ATSR Firecounts
GOME
Good: Additional trace gas measurement of biomass burning; effect can be identified largely by firecounts (see below)
Bad: Observed HCHO a mixture of biogenic and pyrogenic – difficult to separate without better temporal and spatial resolution
Sep 1997
1997
1998
1999
2000
2001
X = Active Fire (ATSR)
Monthly ATSR Firecounts
Slant Column HCHO [1016 molec cm-2]
Nov 1997
Day of Year

17. HCHO and Isoprene over the Amazon
In situ isoprene 2002
Trostdorf et al, 2004
1997
1998
1999
2000
2001
GOME
ATSR Firecounts used to remove HCHO from fires

18. Can isoprene explain the observed magnitude and variance of HCHO columns over the tropics?
Africa
Isoprene
Limonene
Beta-pinene
[ppb]
Time of Day
Amazon
emission rate (C)
(µg g-1 h-1)
PAR
(µmol m-2 s-1)
assimilation (C)
(mg g-1 h -1) 1 2 3 4 5 6
limonene
myrcene
b-pinene
a-pinene
sabinene
500
1000
1500
00:00
06:00
12:00
18:00
local time [hh:mm] 10 20 30 40
temperature
[°C]
G93 for isop.
[sum of monoterpenes]
transpiration
(mmol m-2 s-1)
monoterpene emission of Apeiba tibourbou
C/o J. Kesselmeier
C/o J. Saxton A. Lewis

19. OMI gives a better chance of estimating African BVOCs
May
Jun
Jul
Aug
Sep
Oct
OMI Data c/o Thomas Kurosu; horizontal resolution O(10x25 km2)

20. Isoprene concentrations during AMMA July 2006 measured by the Bae146 aircraft; MODIS tree cover overlaid
[ppt]
OMI
ATSR Firecounts
Jul
Jul
Isoprene data c/o Jim Hopkins and Ally Lewis, U. York

21. Compiled from UK ozone network data
An increasing role for BVOCs in UK air quality?
“Normal” airmass flow
Stagnant airmass flow
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 5 10 15 20 25 30 35 40
Temperature (C)
Isoprene (ppt)
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 is normally 2-50 ppt
No temperature dependence given!!!!
Same latitude as hudson bay!!
Isoprene c/o Ally Lewis

22. The European Heatwave of 2006
Jun
Jul
Aug
Stewart et al, 2003
Isoprene
Monoterpenes
BVOC fluxes for a “hot, sunny” day
No temperature dependence on isoprene emission….spruce plantation on the borders…
Tropospheric O3 production results from NO + RO2  NO2 + RO
The influence of different VOCs on this step can be calculated
Much higher total rate of NO  NO2 conversion during the heatwave period (NB – the graphs have different scales)
Isoprene contributes substantially to O3 production
Given the short lifetime of isoprene, it must have been generated and reacted locally
Satellite observations test bottom-up emission inventories used for air quality: an important step toward regional chemical weather forecasting

23. Final Comments
Proper interpretation of HCHO requires an integrated approach, i.e., including surface data, lab data
Interpreting space-based HCHO data is still in its infancy – new instruments bring better resolution but also new challenges
With the frequency of European heatwaves projected to increase the role of BVOCs in future UK air quality must be better quantified