KeyBio pipeline for bioinformatics and data science
Karppinen, Tomi: Vertical Distribution of Arctic Methane in 2009–2018 Using Ground-Based Remote Sensing
1. Vertical distribution
of Arctic methane
in 2009–2018 using
ground-based
remote sensing
Tomi Karppinen1, Otto Lamminpää1, Simo
Tukiainen1, Rigel Kivi1, Juha Hatakka1, Marko
Laine1, Huilin Chen2, Hannakaisa Lindqvist1
and Johanna Tamminen1
1)Finnish Meteorological Institute
2) University of Groningen
3.6.2020 Tomi Karppinen
2. Sodankylä FTS instrument
2
See also: Poster by Kivi et al., Remote
sensing and in situ measurements of
greenhouse gases at Sodankylä, Finland.
12. Reference measurements used
12
AirCore: ~100 m long coiled steel tube
lifted up to 30 km with a meteorological
balloon collecting atmospheric profile
inside the tube while descending;
Analysed with Picarro gas-analyzer.
ACE-FTS onboard SCISAT: Fourier
transform spectrometer measuring in
solar occultation mode retrieving
atmospheric profiles of various
parameters and gas concentrations
16. Summary
• We have applied a profile retrieval method to a 10-year data set of ground-based
FTS measurements
• The method is applicable to any ground-based high resolution near infrared spectra
• The retrieved profiles agree well with other profile measurement methods
• Trend analysis shows smaller growth rate towards the end of the time series in the
troposphere
• Variable concentrations and high uncertainties hide the trends in the stratosphere
but the analysis suggest rise in the stratospheric methane concentrations since
2017
• The results have already been utilized in verifying inverse model results from
Carbon Tracker Europe and they reveal discrepancies in high altitudes but further
studies are needed.
16
17. References
• Karppinen, T.; Lamminpää, O.; Tukiainen, S.; Kivi, R.; Heikkinen, P.; Hatakka, J.; Laine,
M.; Chen, H.; Lindqvist, H.; Tamminen, J. Vertical Distribution of Arctic Methane in 2009–
2018 Using Ground-Based Remote Sensing. Remote Sens. 2020, 12, 917.
https://doi.org/10.3390/rs12060917
• Tukiainen, S., Railo, J., Laine, M., Hakkarainen, J., Kivi, R., Heikkinen, P., Tamminen, J.
(2016). Retrieval of atmospheric CH 4 profiles from Fourier transform infrared data using
dimension reduction and MCMC. Journal of Geophysical Research: Atmospheres,
121(17), 10,312-10,327. https://doi.org/10.1002/2015JD024657
• Tukiainen, S. Swirlab retrieval code. https://github.com/tukiains/swirlab/
• Laine, M. DLM toolbox for Matlab. https://mjlaine.github.io/dlm/
The study has been supported by ESA project MethEO, Finnish Academy project
CARBARC and Finnish Academy Center of Excellence of Inverse Modelling
17
Editor's Notes
Fourier Transform Spectrometer, Bruker IFS 125HR, has been operational at Arctic Space Center in Sodankylä, North Finland since 2009.
It is part of the Total Carbon Column Observing Network (TCCON) and the retrieval uses the standard TCCON spectra measured with maximum optical path difference of 45 cm resulting resolution of 0.02cm-1.
We use a rather short microwindow with a few methane absorption lines. About 1,67 micrometer
The vertical information is in the shape of the absorption lines as the lines are narrower at high altitudes with low pressure and temperature in comparison to ground pressure and temperatures where the lines are broadened.
Usually remote sensing methods use prior scaling method to retrieve total column concentrations
-high precision and accuracy in total column can be retrieved
Since 2009
We use a rather short microwindow with a few methane absorption lines. About 1,67 micrometer
The vertical information is in the shape of the absorption lines as the lines are narrower at high altitudes with low pressure and temperature in comparison to ground pressure and temperatures where the lines are broadened.
Rather than trying to find a multiplier to the prior profile to find the best match between modelled and measured spectra we let the profile shape vary. To constrain the retrieval we use dimension reduction and instead of retrieving 100 levels independently we only have 4 parameters to fit. The four singular vectors used are calculated from the semi-empirical prior covariance defined using ACE-FTS methane profiles. We use three different prior profiles, summer, winter and as a special case the polar vortex as Sodankylä often lies below the polar vortex some time during spring.
10 years time series of methane profiles are retrieved. With a quick look the stratospheric spring minima are easily detectable denoting the time when Sodankylä is below the polar vortex and the methane poor air descends from higher altitudes. A careful look also reveals the increasing amount of methane in the troposphere.
Dynamic Linear model is used to define growth rates for each layer independently. Results show a rather steady increase of methane in the troposphere with slower increase until 2011 and from 2017 onwards. In the stratosphere very small changes until 2017 there is a steep rise in the methane concentration.
Dynamic Linear model is used to define growth rates for each layer independently. Results show a rather steady increase of methane in the troposphere with slower increase until 2011 and from 2017 onwards. In the stratosphere very small changes until 2017 there is a steep rise in the methane concentration.
Dynamic Linear model is used to define growth rates for each layer independently. Results show a rather steady increase of methane in the troposphere with slower increase until 2011 and from 2017 onwards. In the stratosphere very small changes until 2017 there is a steep rise in the methane concentration.
We compared the profiles to ballon-borne AirCore measurements and satellite-based ACE-FTS measurements. Both having better vertical resolving power. However the measurement frequency is much higher with FTS based retrieval as solar occultation measurements of ACE-FTS are irregularly spaced and have gaps of 3 months. Aircore measurements require a lot of manual work and it is not possible to have the on daily or even weekly basis.
Against both ACE-FTS and AirCore at 30 km our retrieval turns closer to the prior and at leas in polar vortex situations that leads to large difference. That can be seen as large “bulge” of overestimation in comparison to ACE-FTS between 25 to 35 km. The retrieval is not sensitive to changes above 40 km.
ACE-FTS and Our retrieval method agree on the steep rise of methane concentration in the stratosphere starting around 2017. Also the high growth around 10 km 2012-2014 coincide in ground based retrieval and ACE-FTS.