An Evaluation of Radiative Transfer Simulations of Cloudy Scenes from a Numerical Weather Prediction Model at Sub-Millimetre Frequencies Using Airborne Observations

Round 1

Reviewer 1 Report

RS908455 review attached in text file.

Comments for author File: Comments.txt

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

This study is motivated by launch of EUMETSAT second generation
polar-orbiting weather satellites that will allow to retrieve cloud
ice properties and provide radiances for all-sky NWP data
assimilation. The study builds on existing work (12,13,3). While
waiting for the new satellites to be launched in 2022, brightness
temperatures observed by atmospheric research aircraft are used to
extend earlier the studies to higher frequencies, towards
sub-millimetre wavelengths, that are sensitive to cloud ice
particles. Fine-resolution NWP experiments were run to provide cloud
microphysical properties needed by a dedicated radiation scheme.

This is a well written and structured report that documents the
observations, models and experiments in an appropriate extent. There
are valuable new results and suggestions based on their analysis.

I would suggest to publish the manuscript with a few minor
modifications. I have no comments on the language, evidently well
written by a native speaker. Also, I have not studied the
supplementary material that seems comprehensive.

Detailed comments:

1. Introduction

l.56 (or elsewhere) Could you please comment the possibilities to
benefit from the existing in NWP models radiation schemes, that the
models use both for data assimilation and forecast the 3D SW and LW
radiation fluxes? And the other way round: how to use the present
observations for development of these schemes?

Would be helpful for the reader if in the introduction, the aim of the
present study and its relation to the earlier work would be stated
more explicitly.

2. Observations and models

l. 120. How is the ocean surface wind speed used by radiation schemes?

l. 123. "no distinction is made between non-precipitating and
precipitating cloud ice (i.e. ice and snow)." Do you see any problems
here?

l. 125 "interpolated vertically to a constant pressure grid" . Would
there be any possibilities to avoid interpolations, that always smooth
the details?

l. 205 a and b remain unclearly defined

3. Case studies

No comments

4. Results

l. 305-307 Good way to show the results! By the way, perhaps evident,
but you could explain brightness temperature e.g. in the introduction,
and mention why just this is the most appropriate variable for
comparison.

l. 326 surface emissivity (at different wavelenghts) difference
between land and sea. What would you expect to happen over ice and
snow surfaces? In "all-sky" assimilation such surfaces will be met.

5. Discussion and conclusions

l.482 Physically realistic representation of microphysics over all
wavelenghts would allow/require the use of a unified radiation scheme
for forecast and data assimilation in NWP?

l. 507-509 points to the same direction?

l. 513-514 Would it be possible to suggest what kind of main positive
impact to expect from the ICI observations via NWP data assimilation?
After all, the assimilated radiances will influence specific
prognostic variables of the model. Perhaps this is more for the
introduction, could be come back here.

Author Response

Please see the attachment

Author Response File: Author Response.pdf