GCAP 2.0: a global 3-D chemical-transport model framework for past, present, and future climate scenarios

Murray, Lee T.; Leibensperger, Eric M.; Orbe, Clara; Mickley, Loretta J.; Sulprizio, Melissa

doi:https://doi.org/10.5194/gmd-14-5789-2021

Articles | Volume 14, issue 9

https://doi.org/10.5194/gmd-14-5789-2021

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

https://doi.org/10.5194/gmd-14-5789-2021

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

Articles | Volume 14, issue 9

Model description paper

|

24 Sep 2021

Model description paper |

| 24 Sep 2021

GCAP 2.0: a global 3-D chemical-transport model framework for past, present, and future climate scenarios

Lee T. Murray, Eric M. Leibensperger, Clara Orbe, Loretta J. Mickley, and Melissa Sulprizio

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Final revised paper (published on 24 Sep 2021)
Supplement to the final revised paper
Preprint (discussion started on 27 May 2021)
Supplement to the preprint

Interactive discussion

Status: closed

RC1: 'Comment on gmd-2021-144', Anonymous Referee #1, 06 Jul 2021

This manuscript presents a description and evaluation of the second generation one-way offline coupling between NASA GISS E2.1 GCM and GEOS-Chem CTM (GCAP 2.0). This is an update of the on the initial GCAP framework, with improved GISS meteorology and GEOS-Chem emissions/chemistry.

The authors include a thorough presentation of the meteorological fields and emissions, with a comparison of three types of meteorology: MERRA-2, E2.1 nudged to MERRA-2, and E2.1. The model simulations are intercompared and evaluated against observations for atmospheric constituents (O3, NO2, HCHO, CO, PM2.5; lifetimes of CH4 and CH3CCl3; AOD) and transport tracers (SF6 and radionucleides). This enables a detailed evaluation of transport as well as chemistry and deposition. This paper is a substantial contribution to modeling science and provides a new tool for the community. The paper is well writen and well organized. I recommend publication.

Technical corrections:

Please check the figure captions of Figures 15 onwards as some have a typo “The number in the lower left shows the mean bias of the model with respect to the observations”, which should be lower right.

Line 612: The MODIS instrument is onboard the Aqua satellite (not Aura). Also line 616 should be correscted by adding Aqua.

Citation: https://doi.org/10.5194/gmd-2021-144-RC1
RC2: 'Comment on gmd-2021-144', Anonymous Referee #2, 07 Jul 2021

This manuscript describes the GCAP 2.0 model framework, in which the GEOS-Chem 3D CTM is driven by version E2.1 of the NASA GISS model to simulate past, present, and future atmospheric compositions. The work is built on previous versions of offline coupling between the GISS model and the GEOS-Chem model. This manuscript first explains how the meteorological fields were generated from the GISS E2.1 model, the boundary conditions and emissions taken from latest CMIP6-relevant datasets, and how these data drive the GEOS-Chem model for different time periods. The manuscript then extensively evalute the E2.1 meteorological dataset against a reanalysis product (MERRA-2), the E2.1 product submitted to CMIP6, and an intermediate product in which E2.1 winds were nudged to MERRA-2 winds. The resulting differences in GCAP 2.0-simulated atmospheric composition and chemical diagnostics are also evaluated against observations.

In my view, this paper is extremely well written. It is particularly commendable in its extensive evaluation of the meteorological data sets and chemical diagnostics. I only have a few minor comments. In all, I think this is a great guide for researchers interested in using GCAP 2.0, as well as a great reference for those who are interested in understanding the results from global CTMs. I recommend publication of this manuscript after minor revisions.

Line 18: "... for the recent past...": This reads awkward after the last sentence of the previous paragraph, which is (largely) not an issue of the recent past.

Lines 131-132: This sentence is confusing for readers unfamiliar with GEOS or MERRA-2. Is MERRA-2 a product of GEOS-DAS?

Section 5.1.1, lines 259-264: I am confused by this paragraph. So, does GCAP 2.0 use only CEDS, or does it also use a hybrid emission inventory with CEDS superseded by regional inventories?

Line 438: "There is a slight overestimate within the boundary layer and underestimate above ...": overestimate and underestimate of what? Are the authors referring to 222Rn concentration or its vertical gradient? Please revise to imrpove clarity.

Figure 18: What is the time period examined in this figure?

Citation: https://doi.org/10.5194/gmd-2021-144-RC2
AC1: 'Response to reviewers', Lee Murray, 25 Jul 2021

The comment was uploaded in the form of a supplement: https://gmd.copernicus.org/preprints/gmd-2021-144/gmd-2021-144-AC1-supplement.pdf

Citation: https://doi.org/10.5194/gmd-2021-144-AC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Lee Murray on behalf of the Authors (25 Jul 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (23 Aug 2021) by Fiona O'Connor

AR by Lee Murray on behalf of the Authors (23 Aug 2021)

Short summary

Chemical-transport models are tools used to study air pollution and inform public policy. However, they are limited by the availability of archived meteorology. Here, we describe how the GEOS-Chem chemical-transport model may now be driven by meteorology archived from a state-of-the-art general circulation model for past and future climates, allowing it to be used to explore the impact of climate change on air pollution and atmospheric composition.