The vertical structure of cloud radiative heating over the Indian subcontinent during summer monsoon

Johansson, E.; Devasthale, A.; L'Ecuyer, T.; Ekman, A. M. L.; Tjernström, M.

doi:https://doi.org/10.5194/acp-15-11557-2015

Articles | Volume 15, issue 20

https://doi.org/10.5194/acp-15-11557-2015

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

https://doi.org/10.5194/acp-15-11557-2015

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

Articles | Volume 15, issue 20

Research article

|

21 Oct 2015

Research article |

| 21 Oct 2015

The vertical structure of cloud radiative heating over the Indian subcontinent during summer monsoon

E. Johansson, A. Devasthale, T. L'Ecuyer, A. M. L. Ekman, and M. Tjernström

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Final revised paper (published on 21 Oct 2015)
Supplement to the final revised paper
Preprint (discussion started on 25 Feb 2015)
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 C1120: 'referee review', Anonymous Referee #1, 25 Mar 2015
- AC C4735: 'Response to rewiever 1', Erik Johansson, 10 Jul 2015
RC C1845: 'Comments - Reviewer 2', Anonymous Referee #2, 23 Apr 2015
- AC C4736: 'Response to rewiever 2', Erik Johansson, 10 Jul 2015

Peer-review completion

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

AR by Erik Johansson on behalf of the Authors (10 Jul 2015) Author's response

ED: Reconsider after major revisions (14 Jul 2015) by Timothy Garrett

AR by Erik Johansson on behalf of the Authors (30 Jul 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Aug 2015) by Timothy Garrett

RR by Anonymous Referee #2 (23 Aug 2015)

RR by Anonymous Referee #1 (02 Sep 2015)

Suggestions for revision or reasons for rejection

There is some interesting material in the response of the authors, but
there overall is not too much change in the scientific content of the
paper itself. In terms of figures, the main changes appear to be that mean
profile sidebars have been added to several of the Figures, and Figure 13
is new.

The paper is also still mainly descriptive, rather than offering a new
way of explaining some set of observations. A descriptive paper can be
publishable, in my opinion, if the observations are sufficiently novel
and/or they are arranged in a particular insightful way. I am not
familiar enough with this field to independently determine how novel the
observations are. In terms of presentation style, as I mentioned in my
previous comment, much of the material is presented in the same manner:
e.g. Figs 4, 6, 8, 9, 10, (and all supplementary Figures). These figures
comes across more as an "information dump", with too much detail for the
reader to assimilate, rather than an attempt by the authors to support
some specific argument, or give some explanation for the observed
seasonal and latitudinal progression of cloud radiative heating.

Also at times, the paper still suggests it will deliver more mechanistic
insight than it actually does, and this creates a confusing impression in
the reader. For example, in the abstract, it states: "Profiles of
radiative heating inferred from these observations provide insights into
the role that different clouds play as regulators of the monsoon. Such
information is vital for understanding the relative importance of cloud
radiative versus latent heating." However, the paper is essentially a
compilation of cloud radiative heating rates over the Indian
subcontinent. Due to the complexity of the interactions between cloud
radiative heating, convection, and large scale dynamics, it is difficult,
without a model, to predict how these heating rates might affect
precipitation patterns, TTL dehydration, etc. (And models often are often
not that good either). I don't think the paper gives any new specific
insights on how clouds regulate the monsoon. The argument that they will
affect the monsoonal circulation by warming the atmosphere and cooling
the surface seems obvious, and can't be an original insight. The possibility
mentioned in the conclusion that the decrease in surface heating from
clouds could be responsible for the monsoon "break" periods seems quite
speculative, and outside the scope of the paper.

Nevertheless, there appears to be some interesting aspects of the paper in
terms of the contributions of various cloud types to the vertical
structure of cloud radiative heating over the Indian subcontinent.
So my overall recommendation would be potentially publishable with
revisions.

Other Comments

From my reading of the paper, I didn't see a definition, or reference,
for how the various cloud types, have been defined. I think this is quite
central to the paper and should be in there somewhere.

lines 296 - 298: "Given the distinct monthly variability in cloud
fraction from pre to post monsoon, examining corresponding monthly
variations of CRH provides interesting insights that can be directly
evaluated in the global climate models." However, the material did not
seem to be arranged in a way that would be of direct use to climate
models. In general, climate models can not easily attribute the cloud ice
in the model to the various cloud types (whose definitions are to some
degree intrinsically fuzzy anyway), so segregating the radiative effects
in this way does not make for easy comparison with climate models. Also,
the latitudonal means in each zone would not provide easy comparison with
climate models, since they would likely have errors in their
precipitation patterns. I realize that the use of cloud types does help
with physical insight at times, and that the mean profiles now given
would help with climate model comparisons.

line 232: "rate parameter" not defined.

line 260: "effect of melting layer at around 5 km is also visible .."
How?

Line 400: There is no explanation here of why the atmospheric warming
shown in Figure 13 saturates at a low value of IWP while the surface
cooling continues to cool with increasing IWP.

line 525: "Deep convection has mean cooling effect in absolute terms
above LZRH during both active (- 1.23 K/day) and break periods (-0.36
K/day). However, the active conditions show much wider PDFs of CRH,
suggesting that convective clouds do not always cool the TTL." What must
be meant here is not "Deep convection" or "convection" but rather the
cloud radiative effects of convection (since the paper has no
calculations of convective heating). This is a specific example of how
the paper at times seems to confuse the cloud radiative effects of
convection with convection itself.

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ED: Reconsider after minor revisions (Editor review) (11 Sep 2015) by Timothy Garrett

AR by Erik Johansson on behalf of the Authors (21 Sep 2015) Author's response Manuscript

ED: Publish as is (26 Sep 2015) by Timothy Garrett

AR by Erik Johansson on behalf of the Authors (06 Oct 2015)

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Short summary

Both radiative and latent heat components of total diabatic heating influence Indian monsoon dynamics. This study investigates radiative component in detail, focusing on various cloud types that have largest radiative impact during summer monsoon over the Indian subcontinent. The vertical structure of radiative heating and its intra-seasonal variability is investigated with particular emphasis on the upper troposphere and lower stratosphere (UTLS) region.