Scale dependence of cirrus  heterogeneity effects. Part II: MODIS NIR and SWIR channels

Fauchez, Thomas; Platnick, Steven; Várnai, Tamás; Meyer, Kerry; Cornet, Céline; Szczap, Frédéric

doi:https://doi.org/10.5194/acp-18-12105-2018

Articles | Volume 18, issue 16

https://doi.org/10.5194/acp-18-12105-2018

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

https://doi.org/10.5194/acp-18-12105-2018

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

Articles | Volume 18, issue 16

Research article

|

22 Aug 2018

Research article |

| 22 Aug 2018

Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels

Thomas Fauchez, Steven Platnick, Tamás Várnai, Kerry Meyer, Céline Cornet, and Frédéric Szczap

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Final revised paper (published on 22 Aug 2018)
Preprint (discussion started on 06 Feb 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review', Anonymous Referee #1, 10 Apr 2018
- AC1: 'Reply to referee #1', Thomas Fauchez, 12 Jul 2018
RC2: 'Review of acp-2018-38', Anonymous Referee #2, 19 Apr 2018
- AC2: 'Reply to referee #2', Thomas Fauchez, 12 Jul 2018

Peer-review completion

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

AR by Thomas Fauchez on behalf of the Authors (12 Jul 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (17 Jul 2018) by Johannes Quaas

RR by Anonymous Referee #2 (01 Aug 2018)

Suggestions for revision or reasons for rejection

Dear authors,
I read the response to the review #2 and appreciate that the comments were addressed thoroughly. Thank you for the clarification regarding THEA and TIPA.

One important comment though regarding the transport of photons in inhomogeneous atmospheres: The net transport of photons does not necessarily occur from optically thick to thin regions because the spatial context and scale over which the transport occurs needs to be considered. In some cases, such as the figure that you included in the response, the transport does indeed occur from "thick" to "thin", but imagine a case where a pixel has an optically thicker neighbor right next to it, but then an optically thinner pixel that follows "next door". Which direction does the transport go then? An extreme example for this scenario is an isolated cumulus cell, which obviously has internal variability in terms of the optical thickness, so following the assertion that "bright pixels get darker", and "dark pixels get brighter" that one might make after looking at the stratocumulus figure you included, one would think that this would also happen in the isolated cloud. Instead, almost every pixel in the cloud will get darker because the cloud scatters radiation into the clear-sky regions surrounding it, regardless of the immediate neighbors, which may have a larger optical thickness. This is what I mean by "spatial context" and "spatial scale".

I hope this is making sense; I would like to emphasize that my statement does mean the net effect of the direction of photon transport. There is no set-in-stone correlation between the gradient in optical thickness and the direction and magnitude of net photon transport. This is not just a theoretical assertion, but has been published for observed clouds.

I believe that the manuscript is ready to be published, but I'd like to avoid a statement regarding the direction of net photon transport that is not generally valid.

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ED: Publish subject to technical corrections (01 Aug 2018) by Johannes Quaas

AR by Thomas Fauchez on behalf of the Authors (06 Aug 2018) Author's response Manuscript

Short summary

This paper presents the impact of cirrus cloud heterogeneities and 3-D effects on TOA solar reflectances from 50 m to 10 km spatial resolutions. We have shown that these effects are strongly dependent on spatial resolution as well as solar and viewing geometries and that it is difficult to find an optimal spatial resolution minimizing these various effects.