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Research article

A simple and quick sensitivity analysis method for methane isotopologues detection with GOSAT-TANSO-FTS

Authors
  • Edward Malina orcid logo (Formerly at Imaging Group, Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK)
  • Jan-Peter Muller orcid logo (Formerly at Imaging Group, Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK)
  • David Walton (Formerly at Imaging Group, Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK)

This is version 1 of this article, the published version can be found at: https://doi.org/10.14324/111.444/ucloe.000013

Abstract

Measurements of methane isotopologues can differentiate between different source types, be they biogenic (e.g. marsh lands) or abiogenic (e.g. industry). Global measurements of these isotopologues would greatly benefit the current disconnect between ‘top-down’ (knowledge from chemistry transport models and satellite measurements) and ‘bottom-up’ (in situ measurement inventories) methane measurements. However, current measurements of these isotopologues are limited to a small number of in situ studies and airborne studies. In this paper we investigate the potential for detecting the second most common isotopologue of methane (13CH4) from space using the Japanese Greenhouse Gases Observing Satellite applying a quick and simple residual radiance analysis technique. The method allows for a rapid analysis of spectral regions, and can be used to teach university students or advanced school students about radiative transfer analysis. Using this method we find limited sensitivity to 13CH4, with detections limited to total column methane enhancements of >6%, assuming a desert surface albedo of >0.3.

Keywords: methane, radiative transfer, GOSAT, isotopologue, SWIR, education, outreach

Rights: © 2021 The Authors.

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1Citations

Published on
10 Feb 2021
Peer Reviewed
License
Creative Commons Attribution 4.0

 Open peer review from bingkun luo

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-EARTH.AAKSMZ.v1.RZNNHZ
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Education , Earth & Environmental sciences , Physics
Keywords: Methane , SWIR , Education , Outreach , Climate , GOSAT , Radiative transfer , Isotopologue

Review text

This paper introduces a quick method to detect the methane isotopologues using Radiative Transfer Models. As described by authors, this is just a first step and the retrieval algorithm needs further development. The authors have also investigated the spectral distribution of the methane, and the potential error sources such as from water vapor and SCIATRAN. Overall, it is a clear and well-organized structure. I would recommend accept after only a few minor corrections listed as follows.

Page 1 Line 40  :
“the feasibility” should be “the feasibility of”
Page 2 Line  18:
“ethane” should be “methane”
Page 3 Line 19-21
The abbreviation “GOSAT21-TANSO-FTS” has been defined at Page 1 Line 43-44. Only define the abbreviation at the first time when it is used in the text.
Page  5 Line 16 :
“has significant pedigree ” should be “has a significant pedigree”
Page 9 Line 14:
Remove the extra Kuze et al
Page  11 Line  41:
“which take three” should be “which takes three”
Page  14 Line  33 :
would to be?



Note:
This review refers to round 1 of peer review.

 Open peer review from Peter Dobson

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-EARTH.AIH8CJ.v1.RDFXOQ
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Education , Earth & Environmental sciences , Physics
Keywords: Methane , SWIR , Education , Outreach , Climate , GOSAT , Radiative transfer , Isotopologue

Review text

This is a welcome review of how satellite observations can be used to differentiate between methane from biogenic and industrial sources from the isotope signatures in infra-red absorption. The study is based mainly on the Japanese GOSAT data and it is a good introduction to students about Radiation Transfer Modelling, but with the proviso that the students are already very familiar with infra-red adsorption and light scattering physics.

The paper would have much wider appeal if there were explanatory diagrams about the mechanisms of light scattering/adsorption in an introductory section. For example a simple diagram to explain what the GOSAT-TANSO-FTS actually measures would make a large difference to the understanding of the work and give this much more general appeal. The data permits detection  of 13 CH 4 , and the ratio of 13 CH­­ 4 and 12 CH 4 known as δ 13 C. This subject has a lot of acronyms, and an explanatory box listing these would also be very helpful.

Generally the attention to detail about the modelling is clear, but a reader new to the subject would like to know more about the real utility of this approach. For example it would be useful to see if the methodology has been able to pick out geographical regions where the biogenic  methane dominates the industrial methane, so a spatial map of δ 13 C would be useful.

Finally some comment about the methane released from methane clathrates should be included in the paper. These may assume increasing importance as the Arctic and Antarctic regions warm and release such methane.



Note:
This review refers to round 1 of peer review.