The authors have addressed each of the two reviewers' comments and the
revised manuscript is now much improved.

I recommend publication once a few minor corrections have been made:

1) Abstract, line 3 -- replace "produces synthetic radiance data from any global meteorological model output" with "produces a 'simulated radiance' product from any high resolution general circulation model with interactive aerosol".

2) Abstract, page 19 lines 15-16 -- replace "thus potentially improving model skill" with
"allowing to assess model skill consistently with the retrieval algorithm".

3) Abstract, page 19 lines 17-19 (up to "be controlled.") These two sentences need
to be moved up to be the final 2 sentences of the previous paragraph.

4) Abstract, page 19 line 19 -- with item 3) the sentence currently beginning
"The aerosol properties used in MCARS are directly ingested..." will begin
this paragraph -- that's better to re-organise the text this way because I think this
sentence should be re-worded to instead begin like a new para as "In this paper, we illustrate
the operation of MCARS by deriving simulated radiances from the MERRA
re-analysis of the Goddard Earth Observing system 5 (GEOS-5)". Then
replace the existing text starting the next sentence from "They are prepared
using the..." with "The model aerosol fields are translated into simulated
radiances using the ..."

5) Abstract page 19 line 25 -- insert the word "model" between "computed" and
"radiances" so that is now says "MCARS computed model radiances".

6) Abstract page 20 lines 4-5 -- The sentence beginning "Any operational
algorithm..." seems strangely worded -- avoid the phrase "can be executed
transparently" -- it's not obvious what you mean -- replace instead with
"can be implemented equivalently" -- I think that's rather what you mean..
Similarly the phrase "without being explicitly aware of the specific input
source" also seems inappropriately worded -- suggest to instead finish
this sentence as ", the module being coded flexibly to enable other
approaches to be potentially added in future". Or something like this.

7) Introduction, page 22, line 6 -- the two references here should be
reversed with the Ackermann et al., 2008 put first (papers should be
in chronological order) -- and move full-stop to be after the citations.

8) Introduction, page 22, line 11 -- replace "could" with "can".

9) Introduction, page 23, lines 12-13 -- replace "includes outputs of clouds
and aerosols above a surface" with "simulates clouds and aerosols interactively"
and replace "with simulations" with "with the simulated radiance product derived from the model" or similar.

10) Introduction, page 24, line 1 -- delete the sentence "In sections that
follow we will describe the improved MCARS system" -- that text is not
needed and the rest of the para is fine on its own as is.

11) Introduction, page 24, line 23 -- delete the text ", and, where applicable,
chemistry" and re-word slightly so that part of the sentence instead just
reads "treats the sources and sinks of dust, sulfate, sea salt and black
and organic carbon aerosols". The author rightly identified that there was
no dust chemistry included in this model so it is not appropriate to refer to
that here.

12) Page 25, line 7 -- give reference for this database of volcanic SO2
emissions -- is this the Diehl et al. (2012) ACPD, see below?

13) Page 25, lines 22-24 -- This sentence is incorrect I think. As far as
I am aware, the aerosol re-analysis only assimilates MODIS aerosol
optical depth measurements. The MISR and AERONET measurements
in that Buchard et al. (2015) are used as independent
observations against which to assess the aerosol re-analysis.
Please re-word as "The aerosol re-analysis is produced at three-hour
intervals, with assimilation of bias-corrected aerosol optical depth
from MODIS, and has been evaluated against ground-base sun
photometer measurements (Holben et al., 1998)
and against the Multi-angle Imaging Spectroradiometer (MISR)
satellite instrument (give appropriate reference here -- I'd
suggest Kahn et al., JGR, 2007, see below).

14) page 45 -- correct "J. Q. R. Meteorol. Soc." to "Q. J. R. Meteorol. Soc."


Anthropogenic, biomass burning, and volcanic emissions of black carbon, organic carbon, and SO2 from 1980 to 2010 for hindcast model experiments
T. Diehl, A. Heil, M. Chin, X. Pan, D. Streets, M. Schultz, and S. Kinne

Atmos. Chem. Phys. Discuss., 12, 24895-24954, doi:10.5194/acpd-12-24895-2012, 2012

Kahn, R. A., W.-H. Li, C. Moroney, et al. 2007. "Satellite-derived aerosol optical depth over dark water from MISR and MODIS: Comparisons with AERONET and implications for climatological studies." J. Geophys. Res., 112 (D18): D11205

The authors have addressed the comments I raised in my editor review
and the paper can now proceed to publication.