# Elliptical Structures of Gravity Waves Produced by Typhoon Soudelor in 2015 near Taiwan
## 5 Summary and Conclusions
With similar observation [78], two quasi-monochromatic mesoscale GWs with periods of about 6-9 h and varying horizontal and vertical wavelengths of 300 km (600 km) and 3 km (6 km) were captured before (after) the passage of TC Kelly (1987). In addition, earlier overflights of a tropical cyclone during the Stratosphere-Troposphere Exchange Project (STEP) identified two mesoscales GW structures, propagating upward and eastward, with horizontal wavelengths of about 110 km and 250 km and periods of 6 h over the cloud shield in the UT and LS [74]. The mechanism of convective'mountains' was revealed to be in agreement with the generation of such GWs. Reference [76] derived eastward propagating mesoscale GWs with horizontal and vertical wavelengths of 100-700 km and 3-7 km, respectively, from the simulation of TC Ewiniar (2006). The dominant vertical wavelength and period were about 3 km and 6 h, respectively, during the mature stage of the TC. Previously, Reference [72] simulated GWs with horizontal wavelengths of 300-600 km, periods of 6-11 h, and vertical wavelengths of 3-11 km produced by TC Rusa (2002). In addition, the simulated TC Matsa (2005) also supported the generation of eastward propagating GW modes with periods of 12-18 h but with longer horizontal wavelength of about 1000 km in the LS [18] as observed during TC Hudah in 2000 [12]. High-frequency GWs, with periods \(<\)2 h, horizontal wavelengths of 15-300 km and vertical wavelengths of 2.5-8 km, were also found in observation and simulation [16; 18]. More recently, the WACCM (Whole Atmosphere Community Climate Model) model showed that resolved TC-induced GWs can penetrate into the upper atmosphere [80]. Modes with short (\(<\)300 km), medium (300-600 km), and long (\(>\)600 km) wavelengths might contribute more than 40%, 30%, and 15% of the total zonal momentum fluxes, respectively. To conclude, our study supports the notion that TCs are complex sources of multi-scale GWs in the troposphere and LS. A realistic description of the TC with high vertical resolution is now needed to properly characterize TC-induced GWs as well as sources and GW effects during the TC evolution. In particular, the WN1 wind asymmetry was found to be strongly associated with the production of mesoscale GWs in the LS [20] as well as the presence of GWs in the TC core [28; 75]. Finally, our results supported that TC-induced GWs could be indicative of changes in TC dynamics [26]. Today, high-resolution observational data are needed to explore TC cores at fine scales and to validate recent realistic high-resolution TC modelling. In this framework, FormoSat-3/COSMIC RO data may be an alternative means to cross-check the characteristics of GWs in the future studies as demonstrated in the current investigation. The follow-up mission of FormoSat-3/COSMIC, or FormoSat-7/COSMIC-2, is expected to be launched in 2019. Thus more COSMIC RO observations will be available to improve our knowledge of the TC inner core. In perspective, GW sources and momentum fluxes will be investigated. A 3D animation of the simulation from 6 August 18:00 UTC to 7 August 18:00 UTC 2015, produced by the Weather 3D software developed by Meteo-France, is available at [[https://www.youtube.com/watch?v=1](https://www.youtube.com/watch?v=1) aEDfNNsq4 Wc]([https://www.youtube.com/watch?v=1](https://www.youtube.com/watch?v=1) aEDfNNsq4 Wc). Conceptualization, F.C.M. and Y.-A.L. ; methodology and software, F.C.M. and S.J. ; validation and analysis, F.C.M. ; HPC resources, F.C.M. and F.J.; writing-original draft preparation, F.C.M. ; writing-review, F.C.M., S.J. and Y.-A.L. ; editing, F.C.M. and S.J. ; supervision, F.C.M. and Y.-A.L. ; funding acquisition, F.C.M., F.J. and Y.-A.L. ; 3D visualization software and in-situ data provider: D.M. and J.-S.H. This work was financially supported by grants from the ANRT (CIFRE 2015/0876), French ANR (BOOST3R ANR-17-CE01-0016-01) and Taiwanese MOST (105-2221-E-008-056-MY3, 107-2111-M-008-036).