Numerical Simulation of the Diurnal Cycle of a Precipitation System during KWAJEX by 2D and 3D Cloud-Resolving Models
Round 1
Reviewer 1 Report (Previous Reviewer 2)
The authors aimed to examine the diurnal variations of precipitation during KWAJEX based on 2D and 3D CRM simulations of IWP, LWP, and PKE. The authors discussed the difference and similarity between 2D and 3D simulation of diurnal variations of IWP and LWP and PKE for convective and stratiform cases. I found the manuscript interesting but also required major revisions before considered for publication.
1) It is confusing whether the authors are examining the diurnal cycle of precipitation (as stated in the title) or cloud development (in abstract, L17) or cloud process (in summary, L454). Also not clear is why CRM precipitation is not included. The uahtors compared TRMM precipitation with model large-scale variables (Fig. 3). It shows clear discrepancy between simulated vertical motion and TRMM rainfall. It would be more straightforward to show model precipitation and use analysis to understand the modeled precipitation bias in diurnal cycle.
2) The authors used “low”, “mid”, and “upper” troposphere frequently, but inconsistent way. For example, “lower” on L435 used to be “middle” in other part.
3) L17-19, incomplete sentence
4) Fig. 1. What does the left panel show? Where is the Kwajalein Is located in the left panel? It would be more relevant to show land/sea distribution. Also, since domain average is used, right panel is not necessary for this study as well.
5) L216, 2.5km. Does the small bump in 2D consistent with TRMM?
6) L229-231. Incomplete sentence
7) L232, “negative” should be “positive”
8) L233-236, it depends on temperature and moisture gradient. Southerly doesn’t necessarily correlated with warm/moisture advection. If the background used in the simulation shows that, it should be noted here.
9) L237, maxima (in Fig. 3a). Not clear, please consider to add contour shows the regions with maxima.
10) L242, “maximum upward”, not clear. Please add contour to show the time/altitude with maximum upward motion.
11) L242, “the mid-troposphere (400-65hPa)”. From Fig. 3c, it seems much lower than that.
12) L244-245. Please elaborate this. What does “during the 24 hours” mean?
13) L246-252. Does simulated precipitation diurnal cycle shows a similarity with TRMM? See also my comment #1.
14) L262. The paper is missing in the reference
15) L267, is “t” mean “top”? Recommend to remove this (where i=0,1,…,t) as it is redundant (L263)
16) L283-284, “the observed” should be “the simulated”
17) L282, L286-289, midnight peaks are same in 2D and 3D, but late afternoon peak in 3D seems delayed from the one in 2D. Any thought on this delay?
18) Fig. 4 d1& d2. Not discussed. Or, L308-311 describes this plot?
19) Fig 4 d1 & d2. PKE in 2D is significantly larger than that in 3D. Any thought on this difference?
20) L299, “vertical sum”. If PKE in Fig. 5 is the vertical sum, why the value of PKE in Fig. 5 is a lot smaller than that in Fig. 4?
21) Fig. 5. What is the time interval of IWP+LWP and PKE? Is it from diurnal cycle as in Fig. 4?
22) L311, the last sentence. Not clear. Please elaborate.
23) L388-389. Both LWP+IWP and PKE are lower in 2D. All figures (for the same variable) should have same shading and/or contours.
24) Fig. 8. It also shows PKE is in general larger in 2D. Please also see my comments #19 & 23 (using same shadings)
25) L407, why baroclinic conversion effects are different in convective (mid troposphere) and stratiform (upper troposphere) case?
26) L409-410, “these differences indicates …” I don’t understand what this mean. Please elaborate it.
27) L411, by “scattered distribution”, are you referring Fig. 5? Please clarify this.
28) L424, “it can be deduced that”. Not all IWP and LWP are precipitating. See also my comment #1.
29) L432-434. It more adequate for land precipitation. It may not apply to the study domain, mostly ocean.
30) Fig. 12 shows atmospheric stability change that may be used to explain the diurnal variation of rainfall.
31) Fig. 13 and all other diurnal composite. How was the composite calculated? Vertical velocity is always subsidence in convective case and rising in stratiform case?
32) L184-190. When convective and stratiform grids are selected, was it done for each grid for each output time (i.e. hourly)?
Author Response
Dear Reviewer,
Please see the attachment.
Best Regards.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (Previous Reviewer 1)
I accept most of the responses of the authors, however I still have some concerns and suggestions.
11) Now I understand what the authors mean about LWP. Unfortunately their definitions is different from that is generally used. I suggest to points this difference by mentioning that LWP depends on the depth of the layers (e. g. LWPi(Dzi) ). Furthermore I suggest to move all of the equations were added into an Appendix.
22) The authors did not respond my concern about the underestimation of the ice water content or IWP. Because the IWP is an important variable in this study, the authors cannot neglect to respond this question. Even if they have no idea about the possible reasons they should mentioned this problem, which limits the reliability of their conclusions.
33) The authors wrote in their response:’ Note that the unit of mixing ratios of hydrometeors from 2D and 3D CRM simulations were kg/kg, but they were g/m3 from TRMM data. In order to unify the units, we use the density of each hydrometeor multiply the mixing ratios of hydrometeors from 2D and 3D CRM simulations. Thus, the units for the mixing ratios of hydrometeors were g/m3 in Line 228. The unit in Figure 2 was g/m3, and we apologize for the mistakes we made.’
I hope I misunderstood how they evaluated the values of mixing ratios due to the change of the unit from kg/kg to g/m3. It seems to me that they multiplied by the density of the particles, which is absolutely incorrect. They have to multiply by the density of air, and multiply by 1000 (due to from kg to g). Unfortunately, using the wrong way for the change of the units gives a reasonable results.
44) See my 16th comment. Please give the relevant variable for the cloud hydrometeor and vapor as well. I think it is the mixing ratio.
55) See my 24th comment. I still do not know what the meaning of the cloud fluctuation is. The authors should give the physical variables which fluctuate in time or space or in both.
Author Response
Dear Reviewer,
Please see the attachment.
Best Regards.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report (Previous Reviewer 2)
Thanks for time and effort to address my previous comments
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
Major comments:
The analysis of the vertical profiles of IWP and LWP (Figure 4, 6 and 7) has central importance in paper. However, I do not know how the vertical profile of the IWP and LWP can be generated, and what the physical meaning of it is. At first glance, it does not make any sense to make plot about vertical profile of a variable which was evaluated by vertically integrating the mixing ratio of hydrometeors. Please, clarify how these plots were made.
The reason of the difference between the observed simulated profiles of the ice particles needs (more) explanation. The numerical simulation (both 2D and 3D) significantly underestimates the ice content above the melting level. As consequence the IWP is also underestimated by the numerical models, so any conclusions involving analysis of the IWP data can be misleading. I have some concern about the using of a rather old microphysical scheme was developed 40 years ago. However, the difference can be explained by two possible reasons: (i) The simulated and observed cloud covers agree well, but the numerical model cannot simulate properly the growth of the snowflakes from cloud ice. (ii) The numerical model underestimates the cloud cover above the melting level.
I suggest to make plots about the comparison of the observed and simulated cloud covers, it may help clarify the possible reason of the discrepancy. The applied threshold value of 5x10-6 gkg-1 should be increased by an order 3, because this small value cannot be detected by any observation techniques.
The English of the manuscript should be improved significantly, furthermore there many typos in the manuscript, it should be carefully revised.
Minor comments
I suggest to modify the title of the paper, my suggestion is as follow:
Numerical simulation of the Diurnal Precipitation Cycle during KWAJEX by 2D and 3D cloud resolving model
The content of the abstract should be rewritten. (see details below).
Lines 17 and 22: It is not clearly written. Writing of ‘Comparison of 2D and 3D simulation’ suggests how the results depend on the spatial extent.
Lines 19 and line 21: ‘maxima of PKE’ ? I think, you should clarify this.
Lines 22 – 23: Again, please clarify which statement is refer for the IWP + LWP, and which one for the PKE. Reading the section about the result I recognized that the authors have generated vertical profile for the LWP and IWP. However, it is not clear how it was done, and what is the physical meaning of that.
Lines 29 – 30: This assertion partly contradicts to that at lines 17 – 22.
Lines 37: ‘convective heating’ is sensible heat transport, and not latent heat transport.
Lines 136 – 139: It seems that the horizontal extension of the 2D domain is 2x larger than that of the 3D. Any reason of it?
Line 140: ‘included 41 vertical levels with a time step of 12 s.’ ????
Lines 174 – 179: I am confused about these categories.
Line 192: Please give what characteristic of the hydrometeors are plotted. I guess it is the mixing ratio.
Figure 2: Something is wrong. It seems to me that the vertical profiles of the domain averaged mixing ratios are plotted in the figure. If this is the case the order of 10 gm-3 of liquid water content is unrealistically high. Please, clarify how the mean profiles were generated.
Figure 3. Please, lets the reader know, how the plots in this figure were generated. What kind of averages were evaluated in the case of the velocity components to plot the time evolution of the vertical profiles? What is the orientation of the temperature and vapor advection?
Lines 224 – 225: The section of ‘and IWP and LWP’ should be deleted in the sentence.
Lines 272 – 273: ’ the barotropic transition via vertical momentum vertical transport’ I do not understand this section of the sentence.
Line 275: ‘ dry air, cloud hydrometeors, and water vapour’. You should give the related physical variables (e.g. temperature of dry air).
Figure 5, figure caption: Please add index ‘T’ for the dry air terms.
Figure 6 and Figure 7. Again, I do not understand how these plots were made. The think these plots have some relation with the vertical profiles of the hydrometer mixing ratios. If it is true, I do not understand why the vertical extension of convective region is smaller than that of the stratiform region.
Figure 10. The text in the figure caption suggest that the plots is about the difference of the results of 2D and 3D simulation. However, at top of each panel the spatial dimension of the simulation is written. I am confused.
Lines 390 – 391: see my comment for line 275.
Lines 396 – 398: I do not understand this sentence.
Line 405: ‘high humidity levels’ large relative humidity???
Lines 409 – 411: ‘The enhanced water vapour mixing ratios may be attributed to the reduced saturation mixing ratios or the complex interaction between Kwajalein Island and the ocean.’ The saturation mixing ratio is impacted by the temperature and atmospheric pressure and are not by vapor mixing ratio.
Lines 423 – 424: ‘This indicates that clouds exhibited larger amplitudes in the 2D simulations and fluctuated more notably than those in the 3D simulations.’ What is the meaning of the amplitude of a cloud?
Line 425: Using the word ‘contrast’ is an overstatement.
Reviewer 2 Report
The authors examined the diurnal variations of IWP/LWP and perturbation kinetic energy (PKE) budget over Kwajalein Is using 2D and 3D CRM simulation. The authors discussed the difference between 2D and 3D simulation of diurnal variations as well as the role of PKE on diurnal cycle of IWP/LWP. Comparisons are also conducted for convective vs stratiform cases. I found the manuscript need to be significantly improved before recommended for publication. I suggest to consider my comments/suggestions before resubmission for publication.
1) The title includes “precipitation”, and the authors used the ratio of IWP to LWP to separate convective rainfall from stratiform rainfall. But no rainfall data has shown in this study. Analysis of the diurnal variation of precipitation would be informative to understand clouds and PKE diurnal cycle.
2) I assume that the analysis of PKE is meant to be used for better understanding of the diurnal cycle of clouds (or precipitation) (Lines 249-250). However, PKE and IWP/LWP are discussed separately. No clear connection between two are discussed, other than timing of diurnal peaks.
3) Lines 72-73: Yuter et al 2005 (J. Applied Metero),and 10.1175/1520-0450(2001)040<2151:CORDFT>2.0.CO;2 & references there in)
4) Lines 150-154: Any references?
5) Lines 161-162 “the model results suitably agreed with the observations”, does “the model” mean the model used in this study? Or, the model used in Shie et al. 2003?
6) Fig. 1a. What is the importance of this map? There is no explanation on this map.
7) Fig.2 and Lines 192, 195 “similarity”, please elaborate it.
8) Fig. 4 – 13. Do these plots show domain average? If so, what is the domain used?
9) Line 236, “a certain”, meaning?
10) Line 238, (2) ïƒ (3)
11) Fig. 4 caption: please check labels (a2, a2, b1, b2 do not match with figures)
12) Line 268, “vertically latitudinal”, what does this mean?
13) Lines 309-312: Any references to support this?
14) Lines 314-315: it is not clear from Fig. 6
15) Fig. 8 & 9 & Lines 324- : How does this help to understand the diurnal cycle of IWP and LWP?
16) Line 330, “uniformly”: in time or in space (vertical)?
17) Line 331-334: IWP & LWP in Fig. 4 doesn’t seem to support this.
18) Line 349, “stratiform rainfall area”, if the cloud ratio used in this study is correct, this means “stratiform clouds” not rainfall. Does rainfall show the consistent diurnal variation?
19) Line 349 and Fig. 6-7: How many cases are used for convective and stratiform conditions for each hours?
20) Line 353, “sea breeze transports” & Line 386 “rainfall proparation towards land”: if domain averaged is used (see also comments 8) and the domain is as large as what used in Fig. 2, sea breeze effect would have been all averaged out (Island is 15km2, but the domain is 100-1000 times larger)
21) Line 363, “rainfall peaks were observed in the afternoon” & Line 365: is this based on model results? Please see my comment #1.
22) Fig 10 caption: “temperature” is not shown. Maybe in Fig. 11?
23) Fig. 12: It seems not consistent with IWP and LWP in Fig. 4. Please explain.
24) Line 392, “also exhibited similar diurnal cycle”: Not consistent with Fig. 5.
25) Lines 421-431. This is only place the authors discussed on why 2D and 3D simulations are different. But it is not clear why this is important and why it leads to strong fluctuation. Please elaborate this. Also, also consider to discuss how domain mean PKE impacts the rainfall diurnal cycle.
