Can VHF radars at polar latitudes measure mean vertical winds in the presence of PMSE?
<p>Mean vertical velocity measurements obtained from radars at polar latitudes using polar mesosphere summer echoes (PMSEs) as an inert tracer have been considered to be non-representative of the mean vertical winds over the last couple of decades. We used PMSEs observed with the Middle Atmosp...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/4485/2019/acp-19-4485-2019.pdf |
| Summary: | <p>Mean vertical velocity measurements obtained from radars at polar latitudes
using polar mesosphere summer echoes (PMSEs) as an inert tracer have been
considered to be non-representative of the mean vertical winds over the last
couple of decades. We used PMSEs observed with the Middle Atmosphere Alomar
Radar System (MAARSY) over Andøya, Norway (69.30<span class="inline-formula"><sup>∘</sup></span> N,
16.04<span class="inline-formula"><sup>∘</sup></span> E), during summers of 2016 and 2017 to derive mean vertical
winds in the upper mesosphere. The 3-D vector wind components (zonal,
meridional and vertical) are based on a Doppler beam swinging experiment
using five beam directions (one vertical and four oblique). The 3-D wind
components are computed using a recently developed wind retrieval technique.
The method includes full non-linear error propagation, spatial and temporal
regularisation, and beam pointing corrections and angular pointing
uncertainties. Measurement uncertainties are used as weights to obtain
seasonal weighted averages and characterise seasonal mean vertical
velocities. Weighted average values of vertical velocities reveal a weak
upward behaviour at altitudes <span class="inline-formula">∼84</span>–87 km after eliminating the
influence 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 the
summer mean altitude profile, which are attributed to the sampling issues of
the PMSE due to disappearance of the target corresponding to the certain
regions of motions and temperatures, prevails. Thus the mean vertical
velocities can be biased downwards at the lower edge, and the mean vertical
velocities can be biased upwards at the upper edge, while at the main central
region the obtained mean vertical velocities are consistent with expected
upward values of mean vertical winds after considering ice particle
sedimentation.</p> |
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| ISSN: | 1680-7316 1680-7324 |