1. Detection of anthropogenic formaldehyde over North America by oversampling of OMI data: Implications for TEMPO
Lei Zhu and Daniel J. Jacob

2. HCHO observations from space constrain emissions of highly reactive volatile organic compounds (HRVOCs)
and funding from NASA ACMAP
OMI HCHO columns
Jan 2006
Jul 2006
T.P. Kurosu
HRVOCs
HCHO
h , OH
oxidation
~ 2 hours
< 1 day
anthropogenic biogenic pyrogenic

3. Nigerian air pollution revealed by satellite
OMI formaldehyde
Population: 170 million (+3% a-1)
GDP: $270 billion (+7% a-1) – oil!
Most natural gas is flared
>80% of domestic energy from biofuel, waste
An unusual mix of very high VOCs, low NOx –
What will happen as infrastructure develops?
gas
flaring!
TES
825 hPa
ozone
DJF
1015 molecules cm-2
aerosol (AOD) NO HCHO glyoxal methane
Lagos
Port
Harcourt
MISR
SCIA
Marais et al., 2014

4. Detection of anthropogenic HRVOCs from HCHO over US has been elusive: elevated HCHO is mainly from isoprene
OMI satellite observations of formaldehyde (HCHO) columns, Jun-Aug 2006
HCHO
h , OH
2 hours
oxidation
Millet et al. [2008]
1 hour
isoprene

5. Using non-growing season to avoid isoprene interference doesn’t work – HCHO observations are then below detection limit
GOME data [Abbot et al., 2003]
HCHO detection in winter hampered by
low sun angles
low PBL heights
slow chemistry
Detection limit
(for 1-month average)

6. Problem is that US urban/industrial plumes are small and localized
OMI monthly detection limit of 5x1015 molecules cm-2 ≡ 1 ppb HCHO in 2 km PBL
HCHO ~ 10 ppb observed in cores of urban/industrial plumes but not on scale of OMI pixels (13x24 km2 nadir)
Solve problem by oversampling: achieve spatial resolution finer than pixel size
by temporal averaging
Day 3
Day 2
Day 1
Apply to OMI HCHO May-Aug retrieval on 2x2 km2 grid, 24 km smoothing

7. Oversampled OMI HCHO over eastern Texas (May-Aug 2005-2008)
vegetation
prevailing
wind
Isoprene in green
Large AHRVOC point sources in black

8. Lack of temperature dependence of HCHO in Houston urban core supports anthropogenic attribution
exp[0.11T]

9. Using OMI HCHO to quantify Houston AHRVOC emissions
Integrate HCHO enhancement over area of Houston plume
HCHO source
= 260 ± 110 kmol h-1
= HCHO column
o = background column
Consistent with S = 240 ± 90 kmol h-1 from TEXAQS
[Parrish et al., 2012]
Compare to EPA AHRVOC inventory (NEI 05)
Species
Emission
kmol h-1
HCHO source
ethene 16 27
propene
6.3 12
HCHO
9.4
CH3CHO
1.2
TOTAL 33 49
Background o
EPA inventory is
factor of 5.5 ± 2.4 too low

10. Implications for TEMPO
Instrument
Pixel resolution
HCHO detection limit
(single retrieval)
OMI
13x24 km2
2x1016 molecules cm-2
TEMPO
2x4.5 km2
1x1016 molecules cm-2
TEMPO should perform much better than OMI in detecting AHRVOC emissions
Detecting AHRVOC emissions from oil/gas fields is of particular interest; OMI is marginal, TEMPO has promise.
Staggering TEMPO pixels from day to day would allow oversampling but that does not seem necessary
Observed diurnal variation of urban/industrial plumes will constrain primary vs. secondary HCHO sources