Dear authors,

thank you for your revised manuscript which took into account and addressed the Referees' comments. However, as you can see, while one of the Referees is happy with the paper, the other is not completely and still has some reservations and asks questions that you should answer and clarify before to accept the paper for final publication in ACP. Please consider making a further revision and send an improved manuscript along with the necessary responses to the Referee 2 comments.

Best regards

Dear authors,

thank you for your revised manuscript, which tried to address the issues raised by the Referees. The current version is greatly improved, but there are still a few rather minor issues.

More specifically, the most important one is that you should take care to avoid confusion between the terms “radiative forcing” and “radiative cooling rates”, which are different and must be clearly differentiated to each other. You should use the appropriate terms in the paper. When discussing Fig. 9, you should refer to cooling rates (K/day), while discussing Fig. S2 you should refer to radiative forcings (W/m2).

Please, look at the comments of the two Referees, address the raised issues and provide a further revised manuscript that should be accepted for publication in ACP.

best regards

Dr Nikos Hatzianastassiou
Atmospheric Chemistry and Physics (ACP) Editor
Associate Professor
Laboratory of Meteorology
Department of Physics
University of Ioannina
45110 Ioannina
Greece

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Referee-1

Dear Editor

As a Referee #1 I have not access any more on the paper of Sun et al..
However, I have read through the reply to Referee #2 and I have some
comments which I pass to you.

1) In their response they mention and added to the Discussion Section
(Page
10–11) the following:
"One interesting finding of this study is the negative net (SW+LW) direct
radiative forcing in the lower troposphere over the TP (Fig. 9)."

Sorry but this is confusing. Fig. 9 does not show the net SW+LW radiative
forcing but the net SW+LW heating rate! It is often done throughout the
text a confusion between heating rates and clear sky radiative forcing!

In RegCM4, during the run and for a given time step, the radiation scheme
is called two times , one with aerosol set to zero and one with aerosol (in
this case dust aerosols). At each radiative time step, the instantaneous
radiative forcing (at TOA and surface) are calculated respectively by the
difference of TOA and surface net flux with and without aerosol.
Then , if idirect=1 the flux and radiative temperature tendency (calculated
as the divergence of the flux) from the No Aerosol call are passed back to
the model, so the model dynamics and meteorology is not perturbed by
aerosol
in this case.
If idirect=2, then the flux and radiative temperature tendency from the
With
Aerosol call are passed back and the dynamics is perturbed by aerosols.

The true instanteneous radiative forcing is obtained with idirect =1
because:
a1) The With Aerosol and No Aerosol radiative calculation are made
simultaneously with exactly the same atmospheric (T,h,p,q) profiles and
surface albedo, and,
a2 ) these profiles are not pertubed by aerosols during the run.

In this paper there are two 20-year simulations:
b1) The first experiment is a control experiment (CON) with dust emitting
sources both within and outside the TP.
b2) The second experiment is a sensitivity experiment (SEN) where are
turned
off the dust emission in the northern and northeastern TP.

I guess that the authors use idirect =2 for both experiments CON and SEN.
Clear sky instantaneous Radiative Forcing is calculated for idirect=2 but
take into account that this will be slightly different from the calculation
with idirect=1 simply because you have some differentiation in atmospheric
(T,h,p,q) profiles and dust load because of the dust aerosol feedback
effect.
Furthermore the calculated clear sky instantaneous radiative forcing is a
different story from the clalculated SW and LW fluxes and heating rates
simply because in these calculations clouds are present as well as the dust
feedback effects on meteorological parameters. There are also semi-direct
effects which are not discussed at all but could be also estimated.

2) The authors mention "4. Although Fig. 9 shows a negative radiative
forcing over the TP within the lowest 200-300 hPa of the atmosphere, the
net
atmospheric column forcing measured by the
flux difference at surface and TOA, as normally done in the literature, is
still positive (Fig. S2). Thus strictly speaking, by conventional
definition, the direct net radiative
forcing on the whole atmospheric column is still positive on long-term
average (Fig. S2), even though the TP dust results in a cooling effect in
the lower troposphere."

This is really confusing. Fig. S2 shows generally negative dust SW forcing
and positive LW forcing at TOA and surface. My impression is that adding SW
and LW forcing, still you get a negative radiative forcing for most of the
domain both at SRF and TOA.
I would suggest to add LW and SW forcings in Fig. S2 to see the total
radiative forcing.

--------------------------------------------------------------------------------------------
Referee-2

I am quite happy with the new submission by the authors. All my previous
concerns have been addressed and I find the paper much improved and
acceptable for publication. There are a few minor points that the
authors may wish to take into account.

Abstract
"The locally generated TP dust can cause surface cooling far downstream
in eastern Mongolia ..." The authors may want to revise this statement
after the new results show the effect on temperature being moved further
east. Also the same phrase "...downstream in eastern Mongolia..." is
mentioned in p. 9, l. 19.

p. 6, l 28: "...shows larger values..." I apologize for requesting this
change in my previous review. It appears I missed that the authors refer
specifically to the summer values. Please correct it back or rephrase it.

p. 7, ll. 14-17: In my opinion, the authors identified the major cause
of dominant LW cooling as the small dust particle size and the large
ssa. The examination of day and night AOD differences had meaning in the
effort to explain the LW cooling, but it now rather complicates the
paper without showing significant differences. If the authors wish, they
could remove this discussion here and simplify Fig. 6.

Fig. 9: Maybe the colorbar limits (minimum and maximum values) were not
changed between this version and the previous one for comparison
purposes in the review process. However for the final submission, the
authors may consider redefining the limits.

Fig. 14: Although it is a nice addition to the paper, its format is not
very helpful because the map is not visible. Please change it so that it
conforms with the format of e.g. Fig. 3a.

p. 10, l 32: Papers with doi 10.3402/tellusb.v56i4.16439 and
10.5194/acp-12-7165-2012 also demonstrate the large sensitivity of SW
radiative forcing to SSA.

p. 13, ll. 2-3 : "The net atmospheric heating rate was negative over the
TP in heavy dust years as a result of the radiative cooling effects of
the dust aerosols..." The authors may want to clarify that they refer to
the lower troposphere. Otherwise, there is contradiction with their
statement "Thus strictly speaking, by conventional definition, the
direct net radiative forcing on the whole atmospheric column is ...
positive on long-term average..."

Dear authors,

thank you for your revised manuscript, which adequately addressed the comments of the Referees. It is now accepted for publication in ACP. The only change you should make is to remove the number (4) at the beginning of text in line 14, page 11 (page 17 of your uploaded Authors-response file), the number was placed by mistake.


Dr Nikos Hatzianastassiou
Atmospheric Chemistry and Physics (ACP) Editor
Associate Professor
Laboratory of Meteorology
Department of Physics
University of Ioannina
45110 Ioannina
Greece

Tel: ++30 26510 08539
Fax: ++30 26510 08699