Preliminary Evaluation of FY-3E Microwave Temperature Sounder Performance Based on Observation Minus Simulation

Round 1

Reviewer 1 Report

Dear authors,

My comments and suggestions are listed in order of their appearance in the paper.

Line 20) 'depending on the MWTS-III' -  word 'channel' is desirable after MWTS-III;

Line 51) Where are references [4-7] in the text? References to above mentioned instruments (MSU, AMSU, AMSU-A, ATMS, MTWS, MTWS-II) are necessary as well;

Line 78) 'Swath width' would be better than 'width';

Line 88) How 16 km scanner resolution is transformed to 33 km and 60 km spatial resolution declared in Table 1? Is it average of 2x2 points for the 33 km resolution and 4x4 points for the 60 km resolution? A picture presenting  foot print of the satellite cross-scanning antenna on the Earth surface with structure of the observation pixels is desirable;

Table 1) For which integration time the NEdT is specified? 1s or some other?

Table 1) What do double (+/-) frequencies in column 2 mean? Is it heterodyne receiver operating in double sideband mode or two separate direct-gain receivers? Or this simply indicates central frequencies of back-end filter block channels in one receiver? Please, add the paper with several words about the receivers or give a reference;

Line 100) Not all 'the rest of the channels have their weighting functions peaking in upper atmosphere', but only channels 12-17, and for channels 5-11 their weighting functions have maxima located in the troposphere;

Figure 1) For convenience of readers, please specify altitude in kilometers at the right vertical scale;

Line 125) It would be useful here to remind readers that channel 3 of MWTS-III has the same frequency as channel 1 of MWTS-II;

Line 130) For MWTS-II area of cold regions really is larger than that for MWTS-III, but areas of hot regions seem approximately equal  for both instruments;

Figure 2) The Figure 2 is wrongly named Figure 3;

Line 149) How the 6-h observation assimilation time window is determined? As, for example, 0600 UTC+/- 3h or as 0600 UTC - 1200 UTC?

Line 151) '0600 UTC' should be replaced by '0000 UTC';

Line 177) Short physical explanation of data in channels 7 and 12 is desirable as for channel 1;

Line 179) It would be better to mention 'MWTS' as 'MWTS-III';

Lines 201, 210, 212, 219) 'g/kg' should be replaced by 'kg/m^2';

Line 204) Is it possible that interpolation of the ERA5 data to points of the MWTS-III resulted in some smoothing of the ERA5 temperature field in Fig.5b so that maxima of the field decreased and minima increased? What happens if you do the opposite, i.e. if you interpolate the MWTS-III data to points of the ERA5?

Line 215-221 and Figure 6) (The most serious question !) The comparison of the two CLWP clear-sky data ensembles was done for different sizes of pixels. Namely, for ERA5 data the size is 0.25x0.25 degrees (28x28 km at the equator and 18x28 km at 50N and 50S), but for MWTS-III pixel sizes are larger, 33x33 km (or 60x60 km for channels 1 and 2) for all latitudes. Could the reduction in standard deviations of MWTS-III you have obtained (especially in channel 2) be the result of greater spatial smoothing of the temperature field by MWTS-III?

Line 225) Figure 6 capture should be added by words similar to  '... (right scale); difference between the deviations for MWTS-III and ERA5 (black line and shaded region, left scale)' ;

Line 234) It should be better to replace 'significantly' by 'noticeably'. 8% is not so significant value;

Line 270) Words 'or less' may be added after 'about 1.0 K';

Line 271) 'channels 8 and 7' should be replaced by 'channels 1 and 2';

Lines 272-273) Words 'in the upper and lower troposphere' should be replaced by 'in the lower troposphere and above the tropopause' (just the same as in the Abstract);

Line 304) If possible, give some hints to understanding changes in the average and standard deviation of O−B with latitude in the north of 20 °N.

 

Author Response

Dear reviewer,

Thank you for your constructive suggestions in your busy schedule. I have replied your suggestions point by point in the uploaded file.

Author Response File: Author Response.pdf

Reviewer 2 Report

see the attached file, which lists all questions on the raw manuscript.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thank you for your constructive suggestions in your busy schedule. I have replied your suggestions point by point in the uploaded file

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper gave the preliminary evaluation of FY-3E/MWTS radiance performance based on the clear sky radiance simulation over Pacific ocean. First of all, the cloud identification using the two window channels at 23.8 and 31.4 GHz was done by the cloud liquid water path (CLWP) retrieval over oceans and the effective discrimination of clear-sky data and cloudy-sky data can provide the appropriate observation error characteristics. This study analysized the difference between observed and simulated brightness temperature (O-B) under the clear sky points and shown its dependence of the observation angle and latitude. The absolute O-B bias under the clear sky point is in general less than 2.0 K and the standard deviations of O-B for all the mid- and upper tropospheric sounding channels are significantly smaller than those channels in the lower troposphere and above the tropopause. This job provided good  indicator before the FY-3E/MWTS data assimilation. This paper can be published after minor revision. there are some comments for the draft revision.

(1) the title of paper should be changed into limitation focus on the usage of observation simulation for the performance evaluation.  

(2) suggest the abstract is reorganized for indication of the main topic. the CLWP is just one step for MWTS performance, not the main job.

(3)line 16 "geolocations" is changed into " location latitude".

(4) in section 5, the variation of O-B characteristic distribution  is separated into the results showing by ascend and descend orbit. The user can know the difference of bias and deviation at ascend and descend orbit.

(5)in the conclusion should mention whether the FY-3E/MWTS-III is good or not for NWP assimilation application. or mention that other further job will be done before the data is used into the NWP assimilation.

Author Response

Dear reviewer,

Thank you for your constructive suggestions and affirmation of our work in your busy schedule. The uploaded file is my point-by-point response to your comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1. at page 5, line 204, 'The value difference around the clod areas are about 5-10K', the word 'clod' should be 'cold'.

2. Line 225 and 229 at page 6, "the early-morning-orbit satellite" should be deleted since it has been described above.

3. The "avoid" in the sentence of "ocean can well avoid the surface emissivity errors" at line 328 seems be better replaced with "reduce".

4.Section 4. "O-B" should be inserted before " variation characteristics with MWTS-III field of view and regions".

5. Missed "to " between"FY-3E complement' and " the present morning and afternoon satellite very well" at line 782 in section 5.

Author Response

Dear reviewer,

Thank you for taking the time to review my manuscript. I have provided a point-by-point response to the your comments in the uploaded file.

Author Response File: Author Response.pdf

Reviewer 3 Report

This revised draft can be accepted and published after check some words and format.

Author Response

Dear reviewer,

Thank you for taking the time to review my manuscript. I have checked the words and format and corrected them.