|The authors put a lot of effort into the revision of the paper, whose presentation is now much improved, and they responded well to my earlier comments. The intention of the paper now comes out clearly and the methodology is very well explained. The paper provides an important step forward in terms of diagnostic indices for MCAOs and identifying regions favourable for PL development. And it is an excellent showcase for the potential of 3D interactive analysis in meteorology. Hence, I am convinced it provides a valuable contribution to WCD. |
I have one main comment and a few minor comments, as detailed in the following:
The collocation of the maximum MCAO depth and the occurrence of a PL is perhaps not too surprising given that PLs often require for their genesis some upper-level forcing in the form of a positive potential vorticity anomaly, as you outline in 3.2.3. Such upper-level positive potential vorticity anomalies are generally associated with an upward doming of the underlying isentropic surfaces (e.g., Hoskins et al. 1985) and, hence, also of the zero-isosurface m_theta_p, leading to reduced stability (and lifting). This relationship is the likely reason why the new MCAO index performs well in predicting PL occurrence; via the upward doming of the upper boundary of the MCAO, it contains implicit information on upper-level forcing. The conventional MCAO index does not contain such information and instead it is purely a measure of the coldness of the CAO air relative to the sea surface. The coldness of the air is likely not the most critical parameter for PL development as long as upper-level forcing is absent. I think the authors should discuss this aspect.
- L50: MCOA -> MCAO
- L80: Even though 3D depiction of atmospheric fields is not the standard, meteorologist are well aware of the potential of 3D visualization since a long time, see for example Figs. 6.12 and 6.14 in Uccellini (1990).
- L102: No need to mention the 37 standard pressure levels on which ERA5 output is available since you are anyway using data on model levels.
- Caption Table 1: Briefly mention in the caption the meaning of the different symbols (e.g., p_tr, p0, p* etc...)
- L173: Maybe rephrase as "... if the lower-level instability extends all the way to the tropopause." or similar. I don't think an MCAO induces an instability, but the instability is rather a defining characteristic of an MCAO.
- L195: Fig. B1 suggests that the lysis point is selected randomly within a circle with a radius corresponding to the mean track distance around the genesis point. Is this correct? The way it is written now, one may think that several such increments are computed.
- L238: Suggest to remove "more realistic insights". I don't think one way or the other of depicting meteorological data is more realistic, but the 3D approach is certainly useful for an interactive exploration.
- L289: delete "in"
Hoskins, B. J., M. E. McIntyre, and A. W. Robertson, 1985: On the use and significance of isentropic potential vorticity maps.
Quart. J. Roy. Meteor. Soc., 111, 877–946, doi:10.1002/qj.49711147002.
Uccellini, L. W., 1990: Processes contributing to the rapid development of extratropical cyclones. Extratropical Cyclones. The Erik Palmen Memorial Volume, C. W. Newton, and E. O. Holopainen, Eds., American Meteorological Society, Boston, USA, 81–105.