An ensemble Kalman filter data assimilation system for the whole neutral atmosphere

Koshin, Dai; Sato, Kaoru; Miyazaki, Kazuyuki; Watanabe, Shingo

doi:https://doi.org/10.5194/gmd-13-3145-2020

Articles | Volume 13, issue 7

https://doi.org/10.5194/gmd-13-3145-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-13-3145-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 7

Development and technical paper

|

13 Jul 2020

Development and technical paper |

| 13 Jul 2020

An ensemble Kalman filter data assimilation system for the whole neutral atmosphere

Dai Koshin, Kaoru Sato, Kazuyuki Miyazaki, and Shingo Watanabe

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Final revised paper (published on 13 Jul 2020)
Preprint (discussion started on 07 Nov 2019)
Supplement to the preprint

Interactive discussion

Status: closed

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

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RC1: 'Review of “An ensemble Kalman filter data assimilation system for the whole neutral atmosphere” by Koshin et al.', Anonymous Referee #1, 05 Dec 2019
RC2: 'Review: "An ensemble Kalman filter data assimilation system for the whole neutral atmosphere" by Dai Koshin et al.', Anonymous Referee #2, 06 Jan 2020
AC1: 'Response to the comments from reviewers', Dai Koshin, 13 Feb 2020

Peer-review completion

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

AR by Dai Koshin on behalf of the Authors (13 Feb 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Apr 2020) by Josef Koller

RR by Anonymous Referee #1 (27 Apr 2020)

Suggestions for revision or reasons for rejection

Review of “An ensemble Kaman filter data assimilation system for the whole neutral atmosphere” by Koshin et al.

The authors have taken the previous reviews into consideration, and revised the manuscript accordingly. In general, I find that their revisions are satisfactory. However, I have a few remaining comments that the authors should address prior to publication.

1. I still do not think that the authors should refer to the Ctrl parameters as “optimal”. This implies that every possible combination of parameters were tested, and these values give the best results. However, only a subset of the near-infinite number of parameter settings were tested. The authors do not know if the results would be marginally improved by, for example, changing the localization length from 600 to 625 km. Because it is not possible to determine the truly optimal parameters, the Ctrl case should really be considered to be the best among what was tested. I thus still am of the opinion that the authors should not refer to these as the optimal parameters.

2. Lines 277-279: The 30 degree spacing is between observations on subsequent orbits. This is different then cross track observations, which would be observations along the same orbit. This statement should be revised accordingly.

3. Line 539: “collection” should be “correction”

4. Lines 538-545: The details about the bias corrections used in previous studies is not entirely correct. For example, Eckermann et al. (2009) state “Here we compute a similar profile over the May–June 2007 period using version 1.07 SABER data, but use it to bias-correct SABER temperatures only at altitudes below 2.7 hPa, where SABER has a 1–3 K warm bias relative to MLS and other instruments (Schwartz et al., 2008; Remsberg et al., 2008). At higher altitudes, V1.07 SABER temperatures appear to be accurate to within (Remsberg et al., 2008) whereas V2.2 MLS temperatures have a vertically structured bias near the stratopause and a systematic cold bias throughout the mesosphere (Schwartz et al., 2008). Thus, at altitudes above we bias-correct MLS temperatures using a profile based on a subjective fit to the various profiles of mean bias of MLS relative to other satellite, suborbital and analysis temperatures plotted in Fig. 26 of Schwartz et al. (2008).” Additionally, Pedatella et al. (2016, doi:10.1002/2016JA022528) indicates that a bias correction has been applied in WACCM+DART. McCormack et al. (2017) does not state explicitly whether or not a bias correction is applied, so it is unclear whether or not a bias correction was used.

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RR by Anonymous Referee #2 (29 Apr 2020)

ED: Publish subject to minor revisions (review by editor) (30 Apr 2020) by Josef Koller

AR by Dai Koshin on behalf of the Authors (10 May 2020) Author's response Manuscript

ED: Publish as is (14 May 2020) by Josef Koller

Short summary

A new data assimilation system with a 4D local ensemble transform Kalman filter for the whole neutral atmosphere is developed using a T42L124 general circulation model. A conventional observation dataset and bias-corrected satellite temperature data are assimilated. After the improvements of the forecast model, the assimilation parameters are optimized. The minimum optimal number of ensembles is also examined. Results are evaluated using the reanalysis data and independent radar observations.