the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Observation of horizontal temperature variations by a spatial heterodyne interferometer using single-sided interferograms
Konstantin Franz Fotios Ntokas
Jörn Ungermann
Martin Kaufmann
Tom Neubert
Martin Riese
Abstract. Analyses of the mesosphere and lower thermosphere suffer from a lack of global measurements. This is problematic because this region has a complex dynamic structure, with gravity waves playing an important role. A limb sounding spatial heterodyne interferometer (SHI) was developed to obtain atmospheric temperature retrieved from the O2 A-band emission, which can be used to derive gravity wave parameters in this region. The 2-D spatial distribution of the atmospheric scene is captured by a focal plane array. The SHI superimposes the spectral information onto the horizontal axis across the line-of-sight (LOS). In the usual case, the instrument exploits the horizontal axis to obtain spectral information and uses the vertical axis to get spatial information, i.e. temperature observations at the corresponding tangent points. This results in a finely resolved 1-D vertical atmospheric temperature profile. However, this method does not make use of the horizontal across LOS information contained in the data.
In this manuscript a new processing method is investigated, which uses single-sided interferograms to gain horizontal across LOS information of the observed temperature field. Hereby, the interferogram is split and each side is mirrored at the center of the horizontal axis. Each side can then be used to retrieve an individual 1-D temperature profile. The location of the two retrieved temperature profiles is analysed using prescribed horizontal temperature variations, as it is needed for deriving wave parameters. We show that it is feasible to derive two independent temperature profiles, which however will increase the requirements of an accurate calibration and processing.
Konstantin Franz Fotios Ntokas et al.
Status: open (until 04 Jul 2023)
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RC1: 'Comment on amt-2023-74', Anonymous Referee #1, 20 May 2023
reply
The manuscript entitled: “Observation of horizontal temperature variations by a spatial heterodyne interferometer using single-sided interferograms” by Ntokas et al. detailed and discussed a new method to derive two independent temperature profiles from 2-D interferograms obtained by a limb sounding spatial heterodyne interferometer. The method makes use of the horizontal information of the 2-D interferogram and is feasible. In general, the manuscript is well written and structured. However, some revisions are needed to be done to improve the work before it can be published.
General and specific points:
To split the 2-D interferogram into two single-side interferograms around the zero optical path difference is the key process to successfully derive two temperature profiles. The temperature information comes mostly from the center of the interferogram, so it would be expected that the temperature retrieval is sensitive to the determination of ZOPD. The authors may consider to add some retrieval results when ZOPD cannot be determined precisely, which could often happen during actual observations.
The text has tendency to omit the definite article "the" in some of its sentences. It is recommended that the authors review and add "the" where needed.
The colored lines in some figures are sometimes difficult to distinguish one from another, e.g., Fig.2(b), Fig. 10(b), Fig. A1(a), and I would suggest to either change the colorbar or use markers if possible.
Line 125-157: For O2 A band, self-absorption cannot be omitted below 90 km. When no self-absorption is assumed for above 80 km, it will affect the temperature retrieval to some extent between 80 km and 90 km. Authors may add some discussions on this.
Line 228-230: "values ..." is not clear in this sentence, please consider to rephrase/complement the sentence.
Technical correction:
Line 18: "...(Vincent (2015))..." would be "(Vincent, 2015)" and also in the other indirect citations in the text, e.g., L32.
Line 20: "...summarize..." would be "summarized"
Line 22: "...point out..." would be "pointed out"
Line 22: "...underline...outlines... " would be "underlined...outlined"
Line 45: “if it it possible...” --> "if it is possible..."
Line 88: "...a electronic transition..." would be "an electronic transition..."
Line 89: "..., which" would be "...., and" /"..., where"
Line 132: "...which..." would be "whose"
Line 138: "...show..." would be "showed"
Line 139: "...1.4 and 1.6 refers..." to "1.4 and 1.6 refer"
Line 325: "...decreases..." to "reduces"
Line 326: duplicated "that" in the sentence
Line 333: "...affects..." to "affect"
Citation: https://doi.org/10.5194/amt-2023-74-RC1
Konstantin Franz Fotios Ntokas et al.
Konstantin Franz Fotios Ntokas et al.
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