the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Comparisons between Polarimetric Radio Occultation Measurements with WRF Model Simulation for Tropical Cyclones
Abstract. A novel radio occultation (RO) technique, polarimetric RO (PRO), has recently been developed to measure differential polarimetric phase shift together with traditional RO products such as temperature and moisture. PRO observations have been shown to be associated with the vertical structure of cloud hydrometeors. With this unique measurement capability, the PRO soundings could potentially be used to evaluate model microphysics. This study compared PRO observations with WRF simulations of three typhoon cases in 2019 and 2021, initialized with ERA5 and NCEP FNL global analysis, respectively, with five microphysics parameterizations (Purdue Lin, WSM6, Goddard, Thompson, and Morrison). There is notable variability in the distribution of the model's hydrometeors, which could be affected by the initial conditions, microphysics parameterization schemes, typhoon locations, and circulation rainbands. The results show that WRF simulation initialized with ERA5 and using the Goddard microphysics scheme performs better in synoptic-scale verification and comparisons with PRO observations. The ensemble mean from 36 ensemble forecasts also exhibits consistent results with the deterministic run. The comparative results demonstrate that PRO data have the potential to evaluate the performance of different microphysics schemes in numerical models.
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RC1: 'Comment on egusphere-2024-3708', Anonymous Referee #1, 21 Mar 2025
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This study explores the use of polarimetric radio occultation (PRO) measurements for validation and verification of different microphysics schemes implemented on a limited area atmospheric model (WRF). Model simulations of typhoon cases are used to simulate the actually observed PRO measurements using a forward observation operator that is similar to the one developed for ECMWF's IFS model previously reported in the AMT journal. The simulated PRO observations are compared to the actual PRO measurements to gain useful insight into which microphysics scheme performs well in simulating PRO observations. Such comparisons will be potentially very useful given the scarcity of measurements direct related to 3-dimensional distribution of hydrometeor particles, and this study is a nice demonstration of this potential.
One of the major difficulties in such a validation approach would be how to account for erroneous representation of the typhoon position in the model. The authors meticulously accounted for this error source by manually relocating the WRF model field so that the model's typhoon position matches with the position from best track data.
The manuscript is very well organized and written in clear language. Flow of logic is also clear and I see no problem in publishing the manuscript as is except for some minor editorial issues.I just point out below some minor edits that the authors may find useful, but I do not think these are essential for acceptance of the manuscript.
Minor comments:
As I understand, when WRF model is initialized, hydrometeor variables are given zero values at the very beginning of the model integration. In such a "cold start" setting for hydrometeor variables, these variables need to be spun-up before any examination is made. It would be informative to readers who may be interested in replicating your experiments or similar experiments if this point (whether the hydrometeor variables were "cold-started") is explicitly explained in section 2.1.
If you did apply cold-start, then I assume the models are integrated for relatively long 18 hours to ensure the model's microphysics is spun-up. If this is the case, this point should also be explained in the manuscript.Figure 8a: Looking from top to below on the right panel, the observed PAZ data is nearly zero at around 2km height and then rapidly increases as the height gets lower, and this behaviour looks unnatural. I suggest the authors check the quality flag for the PAZ data. If the data is flagged unreliable at these heights, I suggest not to show the PAZ data for such lower levels in the graph. Similarly for Figure 8b and Figure 12.
Typographic issues:
Equation (1) and elsewhere: delta phi should be typed with $\Delta \Phi" in LaTeX, not with "\Delta \0" or "\Delta \varnothing" as in the manuscript.
Line 175 and elsewhere: "vortexes" should be "vortices".
Line 177 "Even though": should be replaced with "Despite", or the sentence structure should be revised.
Lines 197, 249 etc. "presented": should be "present"
Line 198 "five schemes however, ...": Start a new sentence with "However", like "...five schemes. However, ..."
Line 269 "-70 degrees": Make it clear that this is Celsius.
Line 296 "contributed by": Probably should be "contributed to by".
Citation: https://doi.org/10.5194/egusphere-2024-3708-RC1
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