Extending the HIRS Data Record with IASI Measurements

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Most of the review comments are responded to and revised appropriately.

One miss print is on p13, line 4, "Figure 8" should be "Figure 9".

Author Response

Most of the review comments are responded to and revised appropriately.

One miss print is on p13, line 4, "Figure 8" should be "Figure 9".

Response:

Thanks for the comments. 

Apologize for the mis-print on page 13 which has been corrected.

Reviewer 2 Report (Previous Reviewer 4)

Geographical plot of HIRS minus IHIRS (perhaps instead of IHIRS) in Figs 2, 4, 5, and 6 should be added.  The current presentation of HIRS and a nearly identical IHIRS is not informative of the geographical location of larger differences.  

Author Response

Geographical plot of HIRS minus IHIRS (perhaps instead of IHIRS) in Figs 2, 4, 5, and 6 should be added.  The current presentation of HIRS and a nearly identical IHIRS is not informative of the geographical location of larger differences.  

Response:

Reviewer's comments are appropriate. For figures 4 and 5, spatial distribution of (IHIRS_DLC-HIRS_DLC) has been added in the middle panel. However, for figures 2 & 6, the separate HIRS_DSC and IHIRS_DSC have ben retained and an additional bottom panel showing the geographical distribution of the difference (IHIRS-HIRS) has been added. Also note comments on page 7 regarding the mis-match of pixels at high latitudes and restricting the bottom scatter plot to 40 S - 40N, etc.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

I could not copy/paste or attach the file of the review report, so I have sent the file by email to Ms. Kelly Ji, directly.

Comments for author File: Comments.pdf

Reviewer 2 Report

This is a technical paper describing the calibration of the older HIRS data with the newer IASI data. As such, it may not be of wide interest, but is an extremely useful and important piece of work for ensuring the consistent and longevity of these important measurements. As a user of the final long-term product and having made many adjustments of ground-based data, I can appreciate the effort that has gone into this. The creation of a standard record at NOAA is welcome and I am a little surprised it has not been set up earlier.

By and large, the paper is clear and well-written. There are quite a few copy-edits to be picked up and I have made some minor points for clarification.

Abstract 1970s no apostrophe

Page 1 para 1 Introduction: missing reference

Page 1/Page 2 expression (differences usage). With the SRFs, there is the prelaunch configuration and changes over time, I gather. Suggest they are introduced in this order. Also you use differences for different types of satellite so for the variations amongst SRFs I would suggest key inconsistencies rather than key differences.

Page 2 2046..

Figure 1 The caption introduces limb-correction before it is introduced in the text. Also the use of hyphens is inconsistent in the caption and subsequent text.

Limb effects: As the measurements are nadir-based non-specialist readers may not be aware of limb-effects and the reasons for correcting these. A sentence or two would help and also strengthen the conclusions.

Reviewer 3 Report

The paper faces the problem to extend data acquired by the multispectral imager HIRS after its replacement with other instrumentation. The authors propose to use data acquired by the hyperspectral sounder (IASI) to simulate HIRS-like data. The paper is in general clear, but some improvements are needed.

Hereby some comments in detail.

a)      The introduction should be improved giving more details on “retrieval techniques for the geophysical parameters”.

b)     In the section “Data and Methodology”, authors should add more details about the HIRS and IASI instruments: in particular IASI spectral resolution, a description of HIRS instrument in terms of instrument type, bands, central wavelength, FWHM , and so on.

c)      It is not fully correct to compare calibration performance using data employed for the evaluation of calibration coefficients. Results obtained using only 2014 and 2015 data should be shown and inserted in the paper.

d)     Pag. 1 the authors cite a “…simple physically-based system (refs)…”, no reference is present. Please give references and  description.

e)     Pag. 10 Typo in caption of Figure 6 “ … FFigure …“

f)       Pag 15 – 16, References.  Delete “[CrossRef]” in references 2, 3, 4, and 5.

 

Reviewer 4 Report

This paper explores the possibility for extending the HIRS measurements with IASI after convolving the high spectral resolution infrared measurements with the HIRS spectral response functions.  The METOP-A platform houses both instruments so direct comparison are made and differences are tabulated as a function of channel, month, clear, cloudy, and orbit (ascending, descending).  It offers interesting and important results but the presentation and figures need to be improved and the effect of HIRS and IASI FOV and sampling differences needs to be discussed.  I recommend a major revision before publication.

Comments

There are several typos that should be fixed.

HIRS channel numbers need to be connected to wavelengths with a table and in the text.

Section 2.3         What is the effect of binning to 0.1 deg?  Is cloud mask 10% screening in IHIRS adequate?  What would the results for 0.05 deg bins or 5% cloud look like?  Since HIRS and IASI collocated FOV have different areal coverage there is the possibility that the cloud cover is different; this would create problems.  For the window channel 8 in clear skies the areal coverage difference would be noticeable at land water interfaces as well as urban vs rural gradients. This should be discussed. 

Section 2.1         Convoluted should be convolved

Section 3.1         Figs 3, 4, and 5 should be changed to present HIRS and difference of HIRS-IHIRS.  The nearly identical plots shown do not inform where the differences are.  I suspect there will be larger differences at cloud edges and broken clouds.

Section 3.2         Figs 6a and 6b.  Any reason for the downward trends with temperature in channels 1 – 3 in the cloudy FOVs? Or the upward trend for window channel 8? Or the opposite trends for the water vapor channels 11 and 12?  

Section 3.2         There should be more discussion comparing cloudy figs 6a and b with clear figs 6c and d.

Section 3.2         Fig 7.  Discuss the opposite dBT prior for clear vs cloud in channels 7 through 11.  Is this note worthy? 

Section 3.2         Table 1.  There are too many significant figures in the table.  Should we really believe or care about differences to 0.0001 K?  Furthermore, what should the reader take from this table.  Is it necessary?

Section 3.2         Fig 8.  This is a nice figure for 13.6 microns a CO2 sensitive channel.  There should be another figure for 6.5 microns, an H2O sensitive channel.

Abbreviations (Acronyms)           Include all that are found in the paper