  Betelgeuse is a pulsating red supergiant whose brightness is semi
periodically variable and in February 2020 reached a historical minimum, the
Great Dimming. The aims of this study are to characterize Betelgeuse's
variability based on available archival data and to study possible causes of
light variability. Many spectra, from ultraviolet and optical regions, were
evaluated for spectral analysis. The spectra were used primarily to determine
radial velocities from different layers of atmosphere and their long{-}term
evolution. Additionally, photometric data were analyzed in different filters as
well, to construct light curves and to determine periods of the variability.
Spectroscopic and photometric variability are compared to each other and given
into a context with the Great Dimming.
  The two most dominant photometric periods are $ P_{1} = 2190 \pm 270 \: \rm d
$ and $ P_{2} = 417 \pm 17 \: \rm d $, while the dominant optical radial
velocity periods are $ P_{1, v_{\rm r}} = 2510 \pm 440 \: \rm d $ and $ P_{2,
v_{\rm r}} = 415 \pm 11 \: \rm d $. In the same time, the radial velocity
determined from ultraviolet spectra also shows variability and is distinctively
different from the variability of photospheric velocity, undergoing longer
periods of variability. We attribute these velocities to the velocities at the
base of outflowing wind. We also report a maximum of stellar wind velocity
during the Great Dimming, accompanied by the previously reported minimum of
brightness and the maximum of photospheric radial velocity. After the Dimming,
Betelgeuse mode of variability has fundamentally changed and is now instead
following a shorter period of $ \sim 200 \: \rm d $.
