the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Exploiting the entire near-infrared spectral range to improve the detection of methane plumes with high-resolution imaging spectrometers
Javier Roger
Luis Guanter
Javier Gorroño
Itziar Irakulis-Loitxate
Abstract. Remote sensing has emerged as an important tool for the detection of methane plumes emitted by so-called point sources, which are common in the energy sector (e.g., oil and gas extraction and coal mining activities). In particular, satellite imaging spectroscopy missions covering the shortwave infrared part of the solar spectrum, such as PRISMA, EnMAP, or GaoFen-5 AHSI, have proven very effective for this application. These instruments sample the methane absorption features at the spectral regions around 1700 and 2300 nm, which enables the retrieval of per-pixel methane concentration enhancements. Data-driven retrieval methods, in particular those based on the matched filter concept, are widely used to produce maps of methane concentration enhancements from imaging spectroscopy data. These maps are being used for the detection of plumes and the subsequent identification of active sources. However, retrieval artifacts caused by particular surface components may sometimes appear as false plumes or disturbing elements in the methane maps, which complicates the identification of real plumes. In this work, we have used a matched filter that exploits a wide spectral window (1000–2500 nm) instead of the usual 2100–2450 nm window with the aim of reducing the occurrence of retrieval artifacts and background noise. This enables a greater ability to discriminate between surface elements and methane. The improvement in plume detection is evaluated through both simulated data and real data from areas including active point sources, such as the O&G industry from the Permian Basin (U.S.) and the coal mines from the Shanxi region (China). Data sets from the PRISMA, EnMAP, and GF5-02 satellite imaging spectrometers missions and from the airborne AVIRIS-NG instrument are used. Results show that the new approach reduces background noise and can remove a great fraction of the retrieval artifacts. For example, the analysis of a scene from the Shanxi region reveals that 15 plumes could be detected from the proposed procedure, whereas only 5 had been identified using the classical matched filter applied to the 2300 nm window. In addition, plume masking derived from this new approach let us propose a new procedure for point source quantification optimized for flux rate values lower than 1000 kg/h.
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Javier Roger et al.
Status: open (until 03 Oct 2023)
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AC1: 'Comment on amt-2023-168', Javier Roger, 18 Aug 2023
reply
- Figure 5 has a mistake. The factor 'f' is defined differently to the Eq. 5. Here I attach the correct figure.
- In Figure 10 caption you can read 'The first two and the last two retrievals were illustrated with a different range of values
in order to compare them by visual inspection'. This is wrong because the figure shows all the retrievals with the same range of values. -
AC2: 'Comment on amt-2023-168', Javier Roger, 18 Aug 2023
reply
- There are other mistakes in Figure 5. Pixel values from the SWIR-MF retrieval that are multiplied by 'f' are those that are LOWER than (<) the 2300-MF retrieval values. And the pixel values from the SWIR-MF retrieval that are directly changed for the 2300-MF retrieval values are those that are GREATER than or EQUAL to (≥) the 2300-MF retrieval values. Here, we attach the corrected Figure 5.
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RC1: 'Review on amt-2023-168', Marvin Knapp, 25 Aug 2023
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Hello,
please find my review attached as a pdf.
Thank you for the insightful manuscript. If you feel that some of my comments are unclear or warrant further discussion, please feel free to address them here before adjusting the manuscript.
Bests, Marvin
Javier Roger et al.
Javier Roger et al.
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