Improving the sectional Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosols of the Weather Research and Forecasting-Chemistry (WRF-Chem) model with the revised Gridpoint Statistical Interpolation system and multi-wavelength aerosol optical measurements: the dust aerosol observation campaign at Kashi, near the Taklimakan Desert, northwestern China

Chang, Wenyuan; Zhang, Ying; Li, Zhengqiang; Chen, Jie; Li, Kaitao

doi:https://doi.org/10.5194/acp-21-4403-2021

Articles | Volume 21, issue 6

https://doi.org/10.5194/acp-21-4403-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Satellite and ground-based remote sensing of aerosol optical,...

https://doi.org/10.5194/acp-21-4403-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 6

Research article

|

22 Mar 2021

Research article |

| 22 Mar 2021

Improving the sectional Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosols of the Weather Research and Forecasting-Chemistry (WRF-Chem) model with the revised Gridpoint Statistical Interpolation system and multi-wavelength aerosol optical measurements: the dust aerosol observation campaign at Kashi, near the Taklimakan Desert, northwestern China

Wenyuan Chang, Ying Zhang, Zhengqiang Li, Jie Chen, and Kaitao Li

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Final revised paper (published on 22 Mar 2021)
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Preprint (discussion started on 14 Sep 2020)

Interactive discussion

Status: closed

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

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RC1: 'Review of Chang et al., 2020', Anonymous Referee #1, 19 Oct 2020
- AC3: 'Reply on RC1', Wenyuan Chang, 29 Dec 2020
RC2: 'review comments', Anonymous Referee #2, 28 Oct 2020
- AC2: 'Reply on RC2', Wenyuan Chang, 29 Dec 2020

Peer-review completion

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

AR by Wenyuan Chang on behalf of the Authors (29 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Jan 2021) by Holger Tost

RR by Anonymous Referee #1 (25 Jan 2021)

Suggestions for revision or reasons for rejection

The authors substantially improved the article based on the reviewers suggestions. Some additional comments and suggestions below

Comments by line:

794. Can you also include here results regarding the angstrom exponent (both for AOD and scattering) to see consistency with the pm2.5 to PM10 ratio? If you are assimilating multiple-wavelenght AOD, one would expect some improvement in the angstrom exponent

834-835. Is not clear why you are making the conclusion on the last sentence of this paragraph. Coarse size bin could influence your results but I wouldn’t assure that it will unless you test it. As you mention in the next paragraph, underprediction of dust extinction efficiency could also be due to the dust sphericity assumption. You also haven’t discuss dust real refractive index up to here that could also influence results. I would leave it as an open question (as you do at the end of the next paragraph). You could also do a sensitivity test increasing dust real refractive index (within observed ranges) to try to match the mass extinction efficiency

883-884. Is this low bias because the assimilation of multiple-wavelenghts? If only one wavelength was being assimilated then a very good fit would be expected

927-962. I appreciate the authors trying to shed some light into this topic. From reading this it looks like BC is interfering in the assimilation process and generating unexpected results. From Fig. 7 it looks like absorption is well modeled by the background simulation for low-dust periods. This would indicate an issue with dust absorption only, not with BC. Thus, I would recommend doing the sensitivity simulations where BC (and maybe all other aerosol species but OIN) is not included as control variable, and thus we can observe how the system responds to changes on dust only. It should also have the desired effect of decreasing SSA as imaginary dust refractive index is increased. Depending on the results these 3 paragraphs could be simplified quite substantially. Also, did you obtained the imaginary refractive index range you tested from literature? If so please state it.

1021-1024. Not sure how you are making this statement if you are not running other aerosol configurations for this case

Minor Edits

51. “which was 55% higher than the radiative forcing value before DA”
152 “equations of the tangent linear model for AOD”
191. You can cite the paper below that implemented the GOCART dust scheme for MOSAIC

Zhao, C., Liu, X., Leung, L. R., Johnson, B., McFarlane, S. A., Gustafson Jr., W. I., Fast, J. D., and Easter, R.: The spatial distribution of mineral dust and its shortwave radiative forcing over North Africa: modeling sensitivities to dust emissions and aerosol size treatments, Atmos. Chem. Phys., 10, 8821–8838, https://doi.org/10.5194/acp-10-8821-2010, 2010.

194. I would erase “for the anthropogenic aerosols” as these size bins are used for all aerosols in the MOSAIC configuration

352. Is “dch(j)” actually “dC_ch(j)”?

635. I would use “inner” or “inner most” or “nested” domain instead of “child”. Keep it consistent with the terms used in section 2.5.

678. Please specify what wavelengths are you assimilating for AOD, scattering and absorption. All of them simultaneously?

731. I would say “with a substantial increase in the third and fourth …” as you don’t have direct observations of aerosol composition

739-750. These sentences are hard to understand. You could replace “We intentionally decreased” by “We performed a sensitivity test decreasing ….”. Also, on the first sentence is not clear if you are decreasing by 30% or 10%. In 744, I would replace “exaggerated” by “increased”. In 750, you mean to say that results are not very sensitive to the correlation length?

762. I would replace “Similarly, WRF-Chem assimilated too much smaller dust particles than the observed” by “’ Similarly, WRF-Chem overpredicted PM2.5 after assimilating both PM2.5 and PM10”

796-804. This paragraph is hard to follow. Is clear from the previous paragraph why the PM2.5/PM10 ratio is getting worse, so I don’t see the need to repeat that here. You could just say that scattering and absorption improve as you are increasing aerosol mass, and scattering improves significantly as it tends to be more sensitive to finer particles which you are improving with AOD assimilation as PM2.5 is getting better

Figure 10. I would restrict the Y axis extent to enlarge the bars, they all look tiny and it’s hard to read.

859-860. I would replace this sentence by “Higher PM10 concentrations were shown in the low atmosphere than at the surface for the assimilation experiments”

868. “Finer aerosol size representation and a better advanced aerosol optical calculation for dust could be considered as solutions”

927. I suggest replacing “trials” by “sensitivity tests”

928 “presented” or “shown” instead of “present”

945. Use “significantly” instead of “a lot”

1046-1047. What do you mean by “Apparently, assimilating PMx alone is not sufficient to accurately estimate the ADRF value.”? Unless you have an observation of ADRF I wouldn’t make this statement.

1056-1058. “The observed SSAsrf (0.78) indicates likely warming forcing of aerosol at Kashi,” why?

1063. I would use “considers” instead of “concern”. Same in 1066

1094. “underestimated” instead of “lowered”. Same for 1134

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ED: Publish subject to minor revisions (review by editor) (26 Jan 2021) by Holger Tost

AR by Wenyuan Chang on behalf of the Authors (02 Feb 2021) Author's response Manuscript

ED: Publish as is (12 Feb 2021) by Holger Tost

AR by Wenyuan Chang on behalf of the Authors (13 Feb 2021)

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Wenyuan Chang on behalf of the Authors (22 Mar 2021) Author's adjustment Manuscript

EA: Adjustments approved (22 Mar 2021) by Holger Tost

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Short summary

Aerosol simulation in WRF-Chem often uses the MOSAIC aerosol mechanism. Still, we need variational data assimilation (DA) for the MOSAIC aerosols to blend aerosol optical measurements. This study provides a developed GSI variational DA system, with a tangent linear operator designed for multi-source and multi-wavelength aerosol optical measurements. We successfully applied the DA system in an aerosol field campaign to assimilate aerosol optical data in northwestern China.