Modeling the global emission, transport and deposition of trace elements associated with mineral dust

Zhang, Y.; Mahowald, N.; Scanza, R. A.; Journet, E.; Desboeufs, K.; Albani, S.; Kok, J. F.; Zhuang, G.; Chen, Y.; Cohen, D. D.; Paytan, A.; Patey, M. D.; Achterberg, E. P.; Engelbrecht, J. P.; Fomba, K. W.

doi:https://doi.org/10.5194/bg-12-5771-2015

Articles | Volume 12, issue 19

https://doi.org/10.5194/bg-12-5771-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-12-5771-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 12, issue 19

Research article

|

12 Oct 2015

Research article |

| 12 Oct 2015

Modeling the global emission, transport and deposition of trace elements associated with mineral dust

Y. Zhang, N. Mahowald, R. A. Scanza, E. Journet, K. Desboeufs, S. Albani, J. F. Kok, G. Zhuang, Y. Chen, D. D. Cohen, A. Paytan, M. D. Patey, E. P. Achterberg, J. P. Engelbrecht, and K. W. Fomba

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Final revised paper (published on 12 Oct 2015)
Supplement to the final revised paper
Preprint (discussion started on 17 Dec 2014)
Supplement to the preprint

Interactive discussion

Status: closed

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

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RC C9279: 'Review of Zhang et al.', Anonymous Referee #1, 14 Apr 2015
RC C9390: 'Review of "Modeling the global emission, transport and deposition of trace elements associated with mineral dust" by Y. Zhang et al.', Anonymous Referee #2, 15 Jun 2015
AC C9415: 'Responses to refree', Yan Zhang, 11 Aug 2015

Peer-review completion

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

ED: Reconsider after major revisions (11 Aug 2015) by Gerhard Herndl

AR by Yan Zhang on behalf of the Authors (12 Aug 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Aug 2015) by Gerhard Herndl

RR by Anonymous Referee #1 (31 Aug 2015)

Suggestions for revision or reasons for rejection

\textbf{Review of the revised version of the manuscript by Zhang et
al, re-submitted to Biogeochemistry in August 2015}

The manuscript by Zhang et al.\ has improved considerably in this
version, compared to the original version. Especially the English,
that has been a bit rough in the first version, has improved a
lot. Also, the authors have answered all my points of criticism, as
well as those by the other reviewer.

To me there remains one small point: I think the authors did not quite
get what I meant with my first criticism. The point that I wanted to
make is that the model treats every element within dust as variable
that is advected and diffused independently from the other
elements. In reality the elements are bound together as dust
particles, and the proper currency for the advection operator would be
particles of differing elemental composition. This situation is
similar to that encountered in modelling plankton cells with varying
elemental composition in the ocean, and here this error has been
assessed by Jim Christian in the paper that I pointed to in my first
review (n.b.\ that is not my paper). To quote from J.\ Christians abstract: "In a population
of cells with varying elemental quotas, the proper currency of the
advection operator is subpopulations of similar cells. The spatial
gradient in total C, N, or P summed over the spectrum of such
subpopulations is identical to that calculated for the population
means, so treating the various elements as independent should
generally be a valid approximation. However, errors can arise in
high-order advection schemes with nonlinear corrector terms, which are
not additive across the subpopulations. Some numerical examples
indicate that these errors are relatively small
[O(10$^{−3}$–10$^{−4}$)] but can be as high as O(10$^{−2}$) in certain
cases. As grid resolution varies, the error scales approximately to
the Courant number."

To this, the authors answer by referring to the more general problem
that no numerical advection oprators is perfectly mass conserving,
monotonic, shape-preserving and computationally efficient. While this
is certainly true, it misses a bit the more specific point I wanted to
make (and then citing the Christian paper does not quite fit). This is
only a question of a little bit reformulation. The main point, that
this error is likely small compared to the main error from uncertainty
in the source distribution of minerals is correct. I would suggest the
authors change one or two sentences here for their final version.

Else I have just one stylistic comment: The authors sometimes use a
percent sign in sentences where they should have used the word
percentage.

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ED: Publish subject to technical corrections (10 Sep 2015) by Gerhard Herndl

AR by Yan Zhang on behalf of the Authors (15 Sep 2015) Author's response Manuscript

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Short summary

A new technique to determine a size-fractionated global soil elemental emission inventory based on a global soil and mineralogical data set is introduced. Spatial variability of mineral dust elemental fractions (8 elements, e.g., Ca, Fe, Al) is identified on a global scale, particularly for Ca. The Ca/Al ratio ranged between 0.1 and 5.0 and is confirmed as an indicator of dust source regions by a global dust model. Total and soluble dust element fluxes into different ocean basins are estimated.