Produce SSW composites for SH events

[kuchaale]

Related to #11.

[kuchaale]

Let's focus on the event from 18 September 2019 (Rao et al., 2020) when all station measurements are available.

[gast-ben]

Analysis was done for the SSW event with onset on 18 September 2019 from 40 days before to 40 days after the onset (09.08.2019 to 28.10.2019). The results can be found in the notebooks for each station.

The northernmost stations (Sodankyla and Kiruna) show an increase in southward wind around the SSW onset corresponding to a peak in the PW activity at the same time.
The NH stations at lower latitudes (CMA and Collm) reproduce the course of the zonal wind of the SH stations during an SSW event on the NH, albeit with different sign.
The SH stations do not show a clear peak of PW activity around the SSW onset how it was the case at the NH for events on the NH. But this may attributed to the fact, that the regarded event is no major one and maybe therefore the forcing may not reach the altitudes above 80 km, which are observed here.