  Despite swift progress in the characterisation of exoplanet atmospheres in
composition and structure, the study of atmospheric dynamics has not progressed
at the same speed. While theoretical models have been developed to describe the
lower layers of the atmosphere and, disconnected, the exosphere, little is
known about the intermediate layers up to the thermosphere.
  We aim to provide a clearer picture of atmospheric dynamics for the class of
ultra hot Jupiters, highly-irradiated gas giants, on the example of WASP-76~b.
  We analysed two datasets jointly, obtained with the HARPS and ESPRESSO
spectrographs, to interpret the resolved planetary sodium doublet. We then
applied an updated version of the MERC code, with added planetary rotation,
also provides the possibility to model the latitude dependence of the wind
patterns.
  We retrieve the highest Bayesian evidence for an isothermal atmosphere,
interpreted as a mean temperature of $3389\pm227$ K, a uniform day-to-night
side wind of $5.5^{+1.4}_{-2.0}\,$ km/s in the lower atmosphere with a vertical
wind in the upper atmosphere of $22.7^{+4.9}_{-4.1}\,$ km/s, switching
atmospheric wind patterns at $10^{-3}$ bar above the reference surface pressure
($10$ bar).
  Our results for WASP-76~b are compatible with previous studies of the lower
atmospheric dynamics of WASP-76~b and other ultra hot Jupiters. They highlight
the need for vertical winds in the intermediate atmosphere above the layers
probed by global circulation model studies to explain the line broadening of
the sodium doublet in this planet. This work demonstrates the capability of
exploiting the resolved spectral line shapes to observationally constrain
possible wind patterns in exoplanet atmospheres, an invaluable input to more
sophisticated 3D atmospheric models in the future.
