Assessment and Correction of View Angle Dependent Radiometric Modulation due to Polarization for the Cross-Track Infrared Sounder (CrIS)
, Henry E. Revercomb 1, David C. Tobin 1, Robert O. Knuteson 1, Michelle L. Loveless 1, Rebecca Malloy 2, Lawrence Suwinski 2, Flavio Iturbide-Sanchez 3, Yong Chen 3, Glen White 4, Joe Predina 4 and David G. Johnson 5
Round 1
Reviewer 1 Report
Title: Assessment and Correction of View Angle Dependent Radiometric Modulation due to Polarization for the Cross-track Infrared Sounder (CrIS)
Authors: Taylor et al.
Summary:
This paper identified that the polarization errors associated with the unprotected gold scene select mirror of CrIS onboard NOAA-series polar-orbiting satellite contribute significantly to the radiometric uncertainty of CrIS, with its most significant impact when viewing cold scene, which therefore limits the complete accuracy of the CrIS measurements. A physical model is proposed in this paper. The errors due to polarization at different wavenumbers are then quantified with this model. Intelligently, this physical bias model's parameters are estimated using the pitch maneuver data of Suomi-NPP and NOAA-20. Impacts of this bias correction model due to polarization are then evaluated by comparing real CrIS observations with and without applying the proposed correction model. Most importantly, this method has been implemented into the NOAA IDPS and NASA L1b calibration algorithms.
The findings of this study are fundamental and extremely important. I recommend minor revisions for this paper.
Recommendation:
Minor revision
Major comments:
I have no severe concerns because this paper is written comprehensively, and the analysis is thorough.
Minor comments:
Line 32 “for a range of scene temperature and types”: missing “.” at the end of this sentence.
Line 80: “FOV is 9”: FOV (Field of View) is not introduced before its usage. Also, in Section 5.2, “field of view” is used instead of FOV. It might be better to be aligned to field of view, or introduce FOV at the beginning and use FOV afterwards.
Line 124 “…provide in the Section 7”: remove “the” between “in” and “Section”.
Line 156: Is it possible to add an appendix showing the equivalence between (4)-(5) and (6)(7)?
Line 203: “When they are perpendicular the transmission is at a minimum”: Add “,” between “perpendicular” and “the”
Line 38: “corresponds to coldest scene”: add “the” before “coldest”
Line 432: “not within scope…”: add “the” before “scope”
Line 486, Figure 10, Line 573, Line 602, Line 605: NOAA20 => NOAA-20 to be consistent.
Line 673: Title of subsection 5.1: Field of regard has been declared as “FOR” at Line 338. It is better to be consistent in this paper. Also, title of subsection 5.2 uses “FOV” instead of “Field of View”. Either way, you might want to keep titles of subsections 5.1-5.2 consistent.
Line 690: “Most notable are the difference in the sensor”: “difference” => “differences”, or “are” => “is”
Line 740 - &41: “of the Planck function that a very small change”: replace “that” with “,”
Line 885: “The second and third panel from the top”: “panel” => “panels”
Line 907-908: “The effect of the polarization…provided”: “effect” => “effects”
Author Response
The author's notes are included in the attached pdf file. Thank you for your thorough review of the manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Polarization errors contribute to the radiometric uncertainty of infrared remote sounders. This paper proposed a model for the polarization induced calibration bias and the associated correction is presented for the CrIS. In my opinion, the structure of the paper is reasonable. There are only some minor issues :
1. In equation (9), what dose the 'Vinst' stand for?
2. In equation (17), if 'Re' is the real part of the complex number?
3. In line 333-335, it is better to explain or to show the magnitude of uncertainty caused by the approximation.
4. In line 484-486, is there some quantitative criterions or principles in data selection? In another word, why the 4 minutes, not 5 minutes of longwave pitch maneuver data selected?
5. In line 624-626, if the authors could give the cost function in the nonlinear least squares fitting?
6. In line 799-800, more details on how to obtain the uncertainty in the combined scene select mirror and sensor polarization, and in the sensor polarization angle.
Author Response
The author's notes to the reviewer are included in the attached pdf file. Thank you for your thorough review of the manuscript.
Author Response File: 
Author Response.docx
