Adaption of an array spectroradiometer for total ozone column retrieval using direct solar irradiance measurements in the UV spectral range

Zuber, Ralf; Sperfeld, Peter; Riechelmann, Stefan; Nevas, Saulius; Sildoja, Meelis; Seckmeyer, Gunther

doi:https://doi.org/10.5194/amt-11-2477-2018

Articles | Volume 11, issue 4

https://doi.org/10.5194/amt-11-2477-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-11-2477-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 11, issue 4

Research article

|

27 Apr 2018

Research article |

| 27 Apr 2018

Adaption of an array spectroradiometer for total ozone column retrieval using direct solar irradiance measurements in the UV spectral range

Ralf Zuber, Peter Sperfeld, Stefan Riechelmann, Saulius Nevas, Meelis Sildoja, and Gunther Seckmeyer

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Final revised paper (published on 27 Apr 2018)
Preprint (discussion started on 28 Sep 2017)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Referee comment', Anonymous Referee #1, 06 Oct 2017
- AC1: 'Author response', Ralf Zuber, 10 Oct 2017
  - SC2: 'More information on filters and stray light correction algorithm needed', Germar Bernhard, 15 Dec 2017
SC1: 'Incorrect units in Figure 4', Germar Bernhard, 15 Dec 2017
- AC3: 'Author response to SC1 and SC2', Ralf Zuber, 11 Jan 2018
RC2: 'Review to Zuber et al., 2017', Anonymous Referee #2, 16 Dec 2017
- AC2: 'Author response to RC2', Ralf Zuber, 11 Jan 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Ralf Zuber on behalf of the Authors (11 Jan 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (16 Jan 2018) by Pawan K. Bhartia

RR by Anonymous Referee #2 (07 Feb 2018)

Suggestions for revision or reasons for rejection

The paper needs to provide adequate description of the stray light “solar band pass” correction method. It also should clearly describe measurements themselves, and give error estimation for the irradiance measurements.

Comments:

1. Who is the manufacture of the spectrometer used in BTS and what is spectrometer model? This is important since a number of studies characterized small spectrometers for stray light and other properties.

2. p. 2, line 16, the authors introduce “1 narrow bandpass filter (298 – 390 nm), and 4 interference filters (center wavelengths: 254, 285, 300 and 400nm)”. Information of the filter manufacture and filter models is needed to evaluate potential light leaks at longer wavelengths (e.g. Hoya U340 filter).

3. P. 2, line 18 states “multiple different combinations of filters, integration times and sub-measurements optimizes the measurement scenario to any kind of specific radiometric application”. The TOC measurements in this paper use 305-310 nm and 340 -350 nm bands. This suggests that only 1 narrow bandpass filter from p.2, line 16 (298 – 390 nm) and maybe an interference filter centered at 300 nm are applicable for TOC measurements.

4. P5, line 16 states “several narrow bandpass filters are used between 280 and 420 nm”. What are they? How the different filter spectra are measured and combined into a single spectrum?

5. A detailed description is needed of the measurement sequence: e.g. rotate filter wheel to position 1 (filter type A), take a measurement at integration time Y (determined by the photon flux), close internal shutter and take a dark current measurement at integration time Y; move to filter wheel position 2 etc. How much time does it take to do the bright measurements out of the total 8 s period for each filter at SZA 30° and 70°?

6. Why 8 s total time was chosen and what signal-to-noise ratio is achieved as a result at 305 and 440 nm at SZA 30° and 70°.

7. Characterization section of the paper should include stray light reduction characterization using filters and FEL in the lab. This is the most important characterization for this instrument. Each filter transmission curve should be presented here with a clear demonstration of reduction of stray light

8. Discussion of irradiance error estimation and method limitations are needed.

9. How is AMF for non-scattered photons calculated? Direct sun AMF at 70° is about 2.8 for O3 profile not 4.5?

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RR by Anonymous Referee #1 (24 Feb 2018)

ED: Reconsider after major revisions (25 Feb 2018) by Pawan K. Bhartia

AR by Ralf Zuber on behalf of the Authors (28 Feb 2018) Manuscript

ED: Publish as is (05 Apr 2018) by Pawan K. Bhartia

AR by Ralf Zuber on behalf of the Authors (06 Apr 2018)

Short summary

A compact array spectroradiometer technology that enables precise and robust measurements of UV spectral irradiance is presented. We show that this instrument can retrieve total ozone column (TOC) accurately. The internal stray light, which is often the limiting factor for measurements in the UV spectral range, is physically reduced so that no other stray-light reduction methods are needed. During an international total ozone measurement intercomparison, the high quality was verified.