The corrections and the remarks from reviewers have benefited to the clarity of the paper.
Nonetheless as mentioned by reviewer no2 the paper needs careful editing and the language
needs to be improved before it can be published in ACP.

First let me make several suggestions that I would like the authors to consider in the next version:

The term 'amplitude' that is used in Tables 2, 3 & 4 is a normalized standard deviation and does not indicate the bias at the station. Could you please add a column to these tables that quantify the bias at each station.

In the supplement it would be rapid to convert reff to r modal, since the reviewer prefers that presentation, I suggest that you make the change.

I propose that you change everywhere in the text 'over sea' with 'over oceanic regions'.

In your answer the the following comment from reviewer 2, you mention adding a sentence to the text.
I am unable to look through the whole paper to try to find this sentence, so please help the editor by pointing out this sentence: I am disappointed that only monthly averages are used (I had hoped for daily data matches). This makes 'the comparison rather general. But when already using monthly average, have you given a thought on comparing the ‘retrieved’ coarse mode aerosol effective radii to those of the AERONET inversion?'

Please substitute the following sentences:
‘ Aerosols in the coarse mode much affect infrared radiation contrary to aerosols in the fine mode. Dust and sea-salt particles are the main components of the coarse mode, the latter usually remaining in the bottom of the planetary boundary layer, to which infrared radiances collected at satellite level are poorly sensitive. ‘
with
'‘ Coarse mode aerosols have a higher contribution to infrared radiation compared to fine mode aerosols. Dust and sea-salt particles are the main components of the coarse mode, the latter usually remaining in the planetary boundary layer, at which altitudes infrared radiances collected at satellite level show poor sensitivity. ‘'

Your answer to the following reviewer comment misses the point he/she is trying to make:
"The CALIOP mean altitude is calculated in this way in order to avoid the critical influence
of the lidar ratio on the estimation of the extinction coefficient (and the optical
depth), which might impact a mean altitude estimation" I do not totally agree. I am
not convinced the authors make best use of the CALIOP products. In dust dominated
regions it should be possible to compare the extinction profile from CALIOP to the dust
occurrence frequency from IASI. I believe this is important to better understand the
differences between the IASI and CALIOP profiles. At the very least this discussion
needs to be extended to the point that a hypothesis is put forward how the bias would
look like. As discussed here and later in the text, it sounds more like an excuse, which
leaves the reader with no conclusion.''

For the following remark, the information missing on your part is what critieria you used to come up with 7%?
'Here, the test distance has been chosen so that about 7% of the items are eliminated."
How much do the IASI results change if the 7% items are included. If one would use the
IASI product one would not have the chance to see which 7% of the cases should be
removed. Any recommendation for users? How shall the IASI be used as a constraint
by climate modellers?''

Please replace the following paragraph:
''A few remarks are necessary to a better understanding of the following analysis. First, the signal induced on IASI observations by each variable of interest, here AOD or altitude, depends on the intensity of the variable. This is however less trivial for the altitude but, generally, the higher the altitude the larger the signal. This is due to the decreasing thermal contrast between the surface and the atmosphere when approaching the surface. For that reason, infrared sounders show a limited sensitivity to the boundary layer. Second, the signal induced by altitude is intrinsically smaller than that induced by AOD: retrieving accurate altitude is more difficult, even more for low AOD. Third, IASI, a remarkably accurate and stable instrument, has a drawback with the larger noise of its short wavelength channels used for a good disentangling of the AOD and altitude respective signals; this difficulty has more impact on the altitude than on the AOD.''
with:
A few remarks are necessary to explain the analysis below. First, the signal induced on IASI observations by each variable of interest, here AOD or altitude, depends on its magnitude. This is however less trivial for the altitude but, generally, the higher the altitude the larger the signal. This is due to the decreasing thermal contrast between the surface and the atmosphere when approaching the surface. Hence, infrared sounders show a limited sensitivity to the boundary layer. Second, the signal induced by altitude is intrinsically smaller than that induced by AOD: retrieving accurate altitude is therefore more difficult, even more so for low AOD. Third, IASI, a remarkably accurate and stable instrument, has a drawback with the larger noise of its short wavelength channels used for a good disentangling of the AOD and altitude respective signals; this difficulty has more impact on the altitude than on the AOD.

With the following remark the reviewer asked for proper English:
''"The box and whiskers results (Fig. 5) are significantly degraded / The Taylor diagram
for the altitude over sea"
Please replace these sentences with:

''The box and whiskers diagram over land (Fig. 5) show results that are significantly degraded compared to the ones over the oceans (Fig. 3). The Taylor diagram that depicts the altitude of the dust layer over the oceans...

This paper can now go into ACP.
It will need in-house copy editing to be more readable to the community.

Yves Balkanski