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. Mean vertical velocity measurements obtained from radars at polar latitudesusing polar mesosphere summer echoes (PMSEs) as an inert tracer have beenconsidered to be non-representative of the mean vertical winds over the lastcouple of decades. We used PMSEs observed with the Middle Atmosphere AlomarRadar System (MAARSY) over Andoya, Norway (69.30 ∘  N,16.04 ∘  E), during summers of 2016 and 2017 to derive mean verticalwinds in the upper mesosphere. The 3-D vector wind components (zonal,meridional and vertical) are based on a Doppler beam swinging experimentusing five beam directions (one vertical and four oblique). The 3-D windcomponents are computed using a recently developed wind retrieval technique.The method includes full non-linear error propagation, spatial and temporalregularisation, and beam pointing corrections and angular pointinguncertainties. Measurement uncertainties are used as weights to obtainseasonal weighted averages and characterise seasonal mean verticalvelocities. Weighted average values of vertical velocities reveal a weakupward behaviour at altitudes ∼84 –87 km after eliminating theinfluence of the speed of falling ice. At the same time, a sharp decrease(increase) in the mean vertical velocities at the lower (upper) edges of thesummer mean altitude profile, which are attributed to the sampling issues ofthe PMSE due to disappearance of the target corresponding to the certainregions of motions and temperatures, prevails. Thus the mean verticalvelocities can be biased downwards at the lower edge, and the mean verticalvelocities can be biased upwards at the upper edge, while at the main centralregion the obtained mean vertical velocities are consistent with expectedupward values of mean vertical winds after considering ice particlesedimentation.

Can VHF radars at polar latitudes measure mean vertical winds in the presence of PMSE?