Geometric considerations of polar mesospheric summer echoes in tilted beams using coherent radar imaging

Sommer, Svenja; Stober, Gunter; Chau, Jorge L.; Latteck, R.

doi:10.5194/ars-12-197-2014

Cited by 8 publications

(9 citation statements)

References 27 publications

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“…The average for a whole month indicates an average drop of −3.5 dB at 25°. The larger drop in power at the edges might be explained by the beam filling effect [ Sommer et al , ] which is not negligible for the oblique beams. We modeled this effect using a thin and homogeneous layer.…”

Section: Resultsmentioning

confidence: 99%

“…As shown in Sommer et al [2014], Δ is small in the middle part of the PMSE, where the beam volume is evenly filled. Δ gets larger toward the upper and lower edges of the PMSE, where the beam filling effect has to be considered.…”

Section: Multibeam Analysismentioning

confidence: 98%

“…Furthermore, we also consider the beam filling factor in tilted beams. As described in Sommer et al [], we calculated the deviation of the mean echo location α from the nominal off‐zenith angle θ , not using coherent radar imaging but the MAOA. The deviation of the mean echo location Δ α = α − θ is calculated for every time and ranges containing PMSE.…”

Section: Multibeam Analysismentioning

confidence: 99%

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On the angular dependence and scattering model of polar mesospheric summer echoes at VHF

2016

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We present measurements of the angular dependence of polar mesospheric summer echoes (PMSE) with the Middle Atmosphere Alomar Radar System in Northern Norway (69.30° N, 16.04° E). Our results are based on multireceiver and multibeam observations using beam pointing directions with off‐zenith angles up to 25° as well as on spatial correlation analysis (SCA) from vertical beam observations. We consider a beam filling effect at the upper and lower boundaries of PMSE in tilted beams, which determines the effective mean angle of arrival. Comparing the average power of the vertical beam to the oblique beams suggests that PMSE are mainly not as aspect sensitive as in contrast to previous studies. However, from SCA, times of enhanced correlation are found, indicating aspect sensitivity or a localized scattering mechanism. Our results suggest that PMSE consist of nonhomogeneous isotropic scattering and previously reported aspect sensitivity values might have been influenced by the inhomogeneous nature of PMSE.

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Section: Resultsmentioning

confidence: 99%

Section: Multibeam Analysismentioning

confidence: 98%

Section: Multibeam Analysismentioning

confidence: 99%

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On the angular dependence and scattering model of polar mesospheric summer echoes at VHF

2016

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“…Although the PMSE occurrence rate reaches almost 100 % during the summer months at Andenes with MAARSY (Latteck and Bremer, 2012), the morphology itself is rather variable. In particular, the layering within PMSE is significant (Sommer et al, 2014) and has to be taken into account when PMSE is used as a tracer for the MLT dynamics. The PMSE layer is affected by tides and GWs, leading to characteristic altitude variations with a minimum occurrence of better strength in the afternoon between 14:00 and 18:00 UTC.…”

Section: Introductionmentioning

confidence: 99%

Observation of Kelvin–Helmholtz instabilities and gravity waves in the summer mesopause above Andenes in Northern Norway

et al. 2018

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Abstract. We present observations obtained with the Middle Atmosphere Alomar Radar System (MAARSY) to investigate short-period wave-like features using polar mesospheric summer echoes (PMSEs) as a tracer for the neutral dynamics. We conducted a multibeam experiment including 67 different beam directions during a 9-day campaign in June 2013. We identified two Kelvin–Helmholtz instability (KHI) events from the signal morphology of PMSE. The MAARSY observations are complemented by collocated meteor radar wind data to determine the mesoscale gravity wave activity and the vertical structure of the wind field above the PMSE. The KHIs occurred in a strong shear flow with Richardson numbers Ri < 0.25. In addition, we observed 15 wave-like events in our MAARSY multibeam observations applying a sophisticated decomposition of the radial velocity measurements using volume velocity processing. We retrieved the horizontal wavelength, intrinsic frequency, propagation direction, and phase speed from the horizontally resolved wind variability for 15 events. These events showed horizontal wavelengths between 20 and 40 km, vertical wavelengths between 5 and 10 km, and rather high intrinsic phase speeds between 45 and 85 m s−1 with intrinsic periods of 5–10 min.

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“…Thus, the number of incoherent integrations is maximized under the condition that the smallest spectral width within PMSE still can be resolved, which was determined for MAARSY to be in the order of 0.8 m/s. The beam pointing was corrected for possible deviations from the nominal beam pointing direction applying Capon radar imaging (Sommer et al, 2014(Sommer et al, , 2016. This corrections seem to be necessary to account for layering tilts and small scale structuring in the PMSE itself.…”

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confidence: 99%

Are mean vertical velocities from PMSE a good representation of mean vertical winds?

Gudadze

Stober

Chau

2018

Preprint

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<p><strong>Abstract.</strong> Mean vertical velocity measurements obtained from Radars at polar latitudes using Polar Mesosphere Summer Echoes (PMSE) as an inert tracer have been considered as non-representative of the mean vertical winds over the last couple of decades. PMSEs observed with the Middle Atmosphere Alomar Radar System (MAARSY) over And&#248;ya, Norway (69.30&#176;&#8201;N, 16.04&#176;&#8201;E) during summers of 2016 and 2017 are used to derive mean vertical winds in the upper mesosphere. The 3D vector wind components (zonal, meridional and vertical) are based on a Doppler beam swinging experiment using 5-beam directions (one vertical and four obliques). The 3D wind components are computed using a recently developed wind retrieval technique. The method includes full non-linear error-propagation, spatial and temporal regularization as well as beam pointing corrections and angular pointing uncertainties. Measurement uncertainties are used as weights to obtain seasonal weighted averages and characterize seasonal mean vertical velocity. Weighted average values of vertical velocities reveal a weak upward behaviour at altitudes 84&#8211;87&#8201;km after eliminating the influence of ice falling speed. At the same time, a sharp decrease/increase in the mean vertical velocities at the lower/upper edges of the summer mean altitude profile prevails, which are attributed to the sampling issues of PMSE due to disappearing of the target corresponding to the certain regions of motions and temperatures. Thus the mean vertical velocities can be biased with decrease up-/down-ward velocity measurements at lower/upper edges, while at the main central region the obtained mean vertical velocities are consistent with expected values of mean vertical winds after considering ice particle sedimentation.</p>

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Geometric considerations of polar mesospheric summer echoes in tilted beams using coherent radar imaging

Cited by 8 publications

References 27 publications

On the angular dependence and scattering model of polar mesospheric summer echoes at VHF

On the angular dependence and scattering model of polar mesospheric summer echoes at VHF

Observation of Kelvin–Helmholtz instabilities and gravity waves in the summer mesopause above Andenes in Northern Norway

Are mean vertical velocities from PMSE a good representation of mean vertical winds?

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