Determination of the vertical distribution of in-cloud particle shape using SLDR mode 35-GHz scanning cloud radar
Abstract. In this study we present an approach that uses polarimetric variables from a scanning polarimetric cloud radar MIRA-35 in the 45° slanted linear depolarization (SLDR) configuration, to derive the vertical distribution of particle shape (VDPS) between top and base of mixed-phase cloud systems. The polarimetric parameter SLDR was selected for this study due to its strong sensitivity to shape and low sensitivity to the wobbling effect of particles at different antenna elevation angles. For the VDPS method, elevation scans from 90° to 30° elevation angle were deployed to estimate the vertical profile of the particle shape by means of the polarizability ratio, which is a measure of the density-weighted axis ratio. Results were obtained by retrieving the best fit between observed SLDR-vs-elevation dependencies and respective values simulated with a spheroid scattering model. The applicability of the new method is demonstrated by means of three case studies of isometric, columnar and oblate hydrometeor shapes, respectively, which were obtained from measurements at the Mediterranean site of Limassol, Cyprus. The identified hydrometeor shapes are demonstrated to fit well to the cloud and thermodynamic conditions which prevailed at the times of observations. Some observations reveal that in mixed-phased clouds ice particle shapes tend to evolve from a pristine columnar or dendritic state at cloud top toward a more isometric shape at cloud base. Either aggregation or riming processes contribute to this vertical change of microphysical properties. The new height-resolved identification of hydrometeor shape and the potential of the VDPS method to derive its vertical distribution are helpful tools to understand complex processes such as riming or aggregation, which occur particularly in mixed-phase clouds.
Audrey Teisseire et al.
Status: final response (author comments only)
- RC1: 'Comment on egusphere-2022-1431', Anonymous Referee #1, 17 Mar 2023
- RC2: 'Comment on egusphere-2022-1431', Anonymous Referee #2, 13 Apr 2023
Audrey Teisseire et al.
Audrey Teisseire et al.
Viewed (geographical distribution)
In this study, the authors show how the vertical distribution of particle shape can be retrieved from the SLDR configuration. Three cases were presented for demonstration and the presented method is shown to be skillful in identifying ice shapes. The method seems to be reasonable, however, the manuscript is difficult to follow. I feel that this manuscript is suitable for readers who are super familiar with this type of work, but is not friendly for people in other fields. I have been working with cloud radars for many years, but it took me very long time to figure out the innovative point of this manuscript. Therefore, I believe the authors should carefully discuss the research progress of this field and highlight the contribution of this work, instead of simply referring to for example Myagkov et al. (2016a). Different observing modes were mentioned in the manuscript, but no explanations were presented. It would be beneficial to summarize the characteristics of different modes in a table, and show why and how this mode is superior to others.
Please see my comments below.
1. I am frustrated in connecting the symbols used this work to existing works. For example, SLDR is denoted by delta_s, rho_hv by rho_s. And polarization ratio, orientation…I took very long time to connect them to what have been used by Myagkov 2016. Other readers may have similar feelings… I would suggest keeping consistent with Myagkov who is the coauthor of this work.
In addition, I feel the first paragraph in section 2.3 is poorly organized. Please elaborate the used variables before analyzing the results in Fig.2.
2. I believe that the Rayleigh condition at Ka-band should be considered. The theoretical basis is based on the assumption of Ka-band Rayleigh scattering which is satisfied for pristine ice. However, in presence of large aggregates which usually occur at -5 to 0 C or -15 C, this assumption is violated and the retrieval should be made with caution.
3. L160-163. the concept of orientation should be well discussed. The reasons why these assumed K values are applicable should be elaborated.
4. The authors claim that rimed or aggregated ice particles are isometric and speculate that the retrieved polarization ratio around 1 indicates riming or aggregation. I feel that this statement should be used with caution. Firstly, the method may be limited to pristine ice at ka band. The Rayleigh condition at Ka band may not have reached, for example at 1.6 km in figure 10. Therefore, the basic assumption is broken. Secondly, very heavily rimed ice can be isometric. Lightly rimed ice or aggregation has a characteristic aspect ratio.
5. I understand that the authors do not have aircraft observations at hand for validation. Why the retrieved results are consistent with cloud physics should be discussed and the weaknees that no direction comparison was done should be discussed.
1. L109. Do you mean that the spectral line with the highest Scx was used? If so, a figure illustrating the spectral processing is needed, since this has rarely been done. In addition, have you quantified the impact of spectral broadening which can effectively smooth the spectral peak?
2. Fig. 3. add discussions about orientation.
3. Fig. 6. Orientation information is missing
4. L174-175. I do not see the discussions about dendritic in your figures.
5. L178-180. The discussion on isometric particle shape class is lack of ground.