Sensitivity Study of Glyoxal Retrievals at Different Wavelength Ranges
Roman
1
Sinreich,
Ivan
1,2
Ortega,
and Rainer
1,2
Volkamer
1Department
of Chemistry, University of Colorado, Boulder, CO; 2Cooperative Institute for Research in
Environmental Sciences, Boulder, CO; [email protected], [email protected]
CARES
Introduction
Glyoxal (CHOCHO) has been increasingly in the focus of scattered sunlight DOAS
measurements. However there is a lack of a common analysis strategy (see Table 1 and Fig.
1) regarding the analysis wavelength range.
Table 1: List of scattered sunlight DOAS glyoxal retrievals reported in peer-reviewed journals
Measure
-ment
Publication
Analysis wavelength range
Value
Type
Method
1
Wittrock et al., 2006
436-457
max. VCD ≥ 1·1015 molec/cm2
satellite
SCIAMACHY
2
Wittrock et al., 2006
436-457
VCD: 2.0–4.1·1014 molec/cm2
urban
MAX-DOAS
3
Sinreich et al., 2007
420-460
max. 140 ppt
urban
MAX-DOAS
4
Sinreich et al., 2007
420-458
max. 350 ppt
marine/coastal
SMAX-DOAS
5
Vrekoussis et al., 2009
435-457
max. VCD > 6·1014 molec/cm2
satellite
SCIAMACHY
6
Vrekoussis et al., 2010
424-457
avg VCD: 4.8·1014 molec/cm2
satellite
GOME-2
7
Lerot et al., 2010
435-460
max. VCD: 8·1014 molec/cm2
satellite
GOME-2
8
Sinreich et al., 2010
433-458
max. 140 ppt
marine
SMAX-DOAS
9
Irie et al., 2011
436-457
median: 81 ppt
urban
MAX-DOAS
10
Coburn et al., 2011
434-460
avg. VCD: 4·1014 molec/cm2
marine/coastal
MAX-DOAS
11
MacDonald et al., 2012
422-442
typ. 0.8-1 ppb
rural
MAX-DOAS
12
Baidar et al., 2013
433-460
max. 274±28ppt
urban
AMAX-DOAS
13
Li et al., 2013
416-441
avg. 0.4 ppb
rural
MAX-DOAS
Fig. 1: Glyoxal and Water vapor
cross-sections convolved with a
slit function of about 0.5 nm
FWHM in the typical glyoxal analysis wavelength range (Volkamer
et al., 2005, Rothman et al.,
2009). Water vapor potentially
interferes with the glyoxal retrieval. In orange, the wavelength
ranges of the measurements of
Table 1 are overlayed.
• For four campaigns glyoxal wavelength sensitivity studies were performed. Two campaigns
were conducted in urban environment and the other two on vessels in the ocean – each
environment with Ocean Optics QE-DOAS and Acton spectrometers. Surprisingly, the deviation
patterns were not much affected by the different spectrometers. They rather show differences
between urban and marine environment.
• The investigated deviation patterns reveal a threshold for the upper analysis wavelength limit at
around 455 nm where the dSCD values become smoother and more consistent. Consequently,
the strong absorption band at 455 nm should be included in the glyoxal analysis in order to more
likely retrieve reliable results. This could be the reason that the two measurements which do not
include the strong band exhibit values outside the expected range (see Table 1).
• According to the investigated spectra, the lower wavelength limit of the glyoxal analysis should
be between 430 and 440 nm to retrieve smoother results.
• More such investigations have to be performed (also for rural areas) in order to find out if the
environment indeed is the driving factor for the deviation patterns. If this is the case then
analysis strategies for different environments could be derived.
6° elevation
angle
20° elevation
angle
10° elevation
angle
Fig. 2: Deviation plots with the upper wavelength range versus the lower wavelength range for a sequence of elevation angles. The colors represent the extent of deviation with respect to an
reference analysis window of 434 to 460 nm. Red means the retrieved dSCD is higher than the reference dSCD, blue it is lower. As expected the higher the elevation angle the more noisy the
values tend to be.
dCSD thresholds in the upper wavelength limit:
• up to about 436 nm (begin of second glyoxal absorption band) leads to strong deviations in the glyoxal
value and apparently unstable fit (The same happens if the analysis window is chosen very small, about
10 nm and smaller).
• at around 441 nm where the water vapor absorption band begins. Retrievals below that typically exhibit
either values significantly higher, or lower in most cases of a lower limit around 425 nm and above.
• at 455/456 nm where the strongest glyoxal absorption band is located. If the absorption window reaches
up to this value or higher the deviations tend to be smaller and more consistent.
dSCD thresholds in the lower wavelength limit:
• around 430 nm where the first glyoxal absorption band ends. Analyses before
this value yield typically lower glyoxal dSCDs and after higher. This is more
pronounced the higher the elevation angle is.
• at around 440 nm with smaller values above this point (where the water vapor
absorption band begins) if the upper wavelength limit is below 455 nm. If the
upper wavelength limit is above 455 nm slightly higher values can be observed
between about 436 and 441 nm.
VOCALS and TAO-2012
Based on Vogel et al. (2013) we compare all possible analysis wavelength ranges between
420 and 460 nm in 0.5 nm steps and a minimum analysis window of 5 nm for analyses of 4
recent measurement campaigns (VOCALS, CARES, TAO-2012 and MAD-CAT). Thereby
spectra with a good signal-to-noise ratio were selected for each campaign. The plots show the
deviations of the retrieval output (differential slant column density and root mean square,
respectively) normalized to an analysis wavelength range of 434 to 460 nm.
Conclusions
3° elevation
angle
1.5° elevation
angle
1.5° elevation
angle
1.5° elevation
angle
Fig. 3: VOCALS:
Left
Top:
Glyoxal
deviations. Left
Bottom: Water
vapor deviations.
For VOCALS the
analyses
with
upper
limits
below 438 nm
did not converge.
Fig. 4: TAO2012: Right Top:
Glyoxal
deviations Right
Bottom:
Respective root
mean
square
deviations.
For
TAO-2012
the analyses with
upper
limits
below 434 nm
did not converge.
MAD-CAT
1.5° elevation
angle
1.5° elevation
angle
VOCALS and TAO-2012 have
similar deviation patterns but
compared to CARES they are a
bit different. Especially, below
about 430 nm lower wavelength
limit it shows higher values, in
opposite to CARES. However,
the thresholds around 440 nm
for the lower wavelength limit
and at 455 nm for the upper
wavelength limit can be found
here too.
As an example, the root mean
square (RMS)
deviation is
shown in Fig. 4. As expected the
RMS generally decreases with
smaller analysis wavelength
ranges.
Also, the water vapor deviation
is shown for VOCALS (Fig.3)
and is typical for all investigated
spectra: The deviation is very
small if the water vapor
absorption band at 442 nm is
completely in the analysis
window. Otherwise strong and
unpredictable values occur.
The
deviation
pattern of the
MPI
measurements
looks
more similar to
the
one
of
CARES.
Particularly inte2° elevation
resting is the
angle
gradient in the
upper
wavelength limit between 455 and
Fig. 5: Glyoxal deviations. 460 nm at lower
For
small
wavelength wavelength limits
ranges the analysis does between 427 and
not converge.
437 nm.
About the Measurements
CARES: Urban, Ocean Optics QE-DOAS
spectrometer
VOCALS: SMAX-DOAS, Marine, Ocean
Optics QE-DOAS spectrometer
TAO-2012: SMAX-DOAS, Marine, Acton
Spectrometer
MAD-CAT: Urban, Acton Spectrometer
REFERENCES:
Baidar, S., Oetjen, H., Coburn, S., Dix, B., Ortega, I., Sinreich, R., and Volkamer, R.: The CU Airborne MAX-DOAS instrument: vertical profiling of aerosol extinction and trace gases, Atmos. Meas. Tech., 6, 719-739, doi:10.5194/amt-6-719-2013, 2013. - Coburn, S., Dix, B., Sinreich, R., and Volkamer, R.: The CU ground MAX-DOAS instrument: characterization of RMS noise limitations and first
measurements near Pensacola, FL of BrO, IO, and CHOCHO, Atmos. Meas. Tech., 4, 2421-2439, doi:10.5194/amt-4-2421-2011, 2011. - Irie, H., Takashima, H., Kanaya, Y., Boersma, K. F., Gast, L., Wittrock, F., Brunner, D., Zhou, Y., and Van Roozendael, M.: Eight-component retrievals from ground-based MAX-DOAS observations, Atmos. Meas. Tech., 4, 1027-1044, doi:10.5194/amt-4-1027-2011,
2011. - Lerot, C., Stavrakou, T., De Smedt, I., Müller, J.-F., and Van Roozendael, M.: Glyoxal vertical columns from GOME-2 backscattered light measurements and comparisons with a global model, Atmos. Chem. Phys., 10, 12059-12072, doi:10.5194/acp-10-12059-2010, 2010. - Li, X., Brauers, T., Hofzumahaus, A., Lu, K., Li, Y. P., Shao, M., Wagner, T., and Wahner, A.: MAX-DOAS measurements of
NO2, HCHO and CHOCHO at a rural site in Southern China, Atmos. Chem. Phys., 13, 2133-2151, doi:10.5194/acp-13-2133-2013, 2013. - MacDonald, S. M., Oetjen, H., Mahajan, A. S., Whalley, L. K., Edwards, P. M., Heard, D. E., Jones, C. E., and Plane, J. M. C.: DOAS measurements of formaldehyde and glyoxal above a south-east Asian tropical rainforest, Atmos. Chem. Phys., 12, 5949-5962,
doi:10.5194/acp-12-5949-2012, 2012. - Rothman, L.S., Gordon, I.E., Barbe, A., Benner, D.C., Bernath, P.F., Birk, M., et al, The HITRAN 2008 molecular spectroscopic database, JQSRT 110, 533-572, 2009. - Sinreich, R., Volkamer, R., Filsinger, F., Frieß, U., Kern, C., Platt, U., Sebastián, O., and Wagner, T.: MAX-DOAS detection of glyoxal during ICARTT 2004, Atmos. Chem. Phys., 7, 1293-1303,
doi:10.5194/acp-7-1293-2007, 2007. - Sinreich, R., Coburn, S., Dix, B., and Volkamer, R.: Ship-based detection of glyoxal over the remote tropical Pacific Ocean, Atmos. Chem. Phys., 10, 11359-11371, doi:10.5194/acp-10-11359-2010, 2010. - Volkamer, R., Spietz, P., Burrows, J., and Platt, U., High-resolution absorption cross-section of glyoxal in the UV–vis and IR spectral ranges, Journal of
Photochemistry and Photobiology A: Chemistry, 172, 1, 35-46, ISSN 1010-6030, http://dx.doi.org/10.1016/j.jphotochem.2004.11.011, 2005. - Vogel, L., Sihler, H., Lampel, J., Wagner, T., and Platt, U.: Retrieval interval mapping: a tool to visualize the impact of the spectral retrieval range on differential optical absorption spectroscopy evaluations, Atmos. Meas. Tech., 6, 275-299, doi:10.5194/amt-6-2752013, 2013. - Vrekoussis, M., Wittrock, F., Richter, A., and Burrows, J. P.: Temporal and spatial variability of glyoxal as observed from space, Atmos. Chem. Phys., 9, 4485-4504, doi:10.5194/acp-9-4485-2009, 2009. - Vrekoussis, M., Wittrock, F., Richter, A., and Burrows, J. P.: GOME-2 observations of oxygenated VOCs: what can we learn from the ratio glyoxal to formaldehyde on a global scale?,
Atmos. Chem. Phys. Discuss., 10, 19031-19069, doi:10.5194/acpd-10-19031-2010, 2010. - Wittrock, F., A. Richter, H. Oetjen, J. P. Burrows, M. Kanakidou, S. Myriokefalitakis, R. Volkamer, S. Beirle, U. Platt, and T. Wagner, Simultaneous global observations of glyoxal and formaldehyde from space, Geophys. Res. Lett., 33, L16804, doi:10.1029/2006GL026310, 2006.