scholarly journals Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

2000 ◽  
Vol 18 (12) ◽  
pp. 1599-1612 ◽  
Author(s):  
P. B. Chilson ◽  
S. Kirkwood ◽  
I. Häggström
Keyword(s):  
Frequency Domain ◽  
Middle Atmosphere ◽  
Lower Boundary ◽  
Doppler Velocity ◽  
Vhf Radar ◽  
Radio Science ◽  
First Results ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Frequency Coherence

Abstract. During the summer of 1997 investigations into the nature of polar mesosphere summer echoes (PMSE) were conducted using the European incoherent scatter (EISCAT) VHF radar in Norway. The radar was operated in a frequency domain interferometry (FDI) mode over a period of two weeks to study the frequency coherence of the returned radar signals. The operating frequencies of the radar were 224.0 and 224.6 MHz. We present the first results from the experiment by discussing two 4-h intervals of data collected over two consecutive nights. During the first of the two days an enhancement of the FDI coherence, which indicates the presence of distinct scattering layers, was found to follow the lower boundary of the PMSE. Indeed, it is not unusual to observe that the coherence values are peaked around the heights corresponding to both the lower- and upper-most boundaries of the PMSE layer and sublayers. A Kelvin-Helmholtz mechanism is offered as one possible explanation for the layering structure. Additionally, our analysis using range-time-pseudocolor plots of signal-to-noise ratios, spectrograms of Doppler velocity, and estimates of the positions of individual scattering layers is shown to be consistent with the proposition that upwardly propagating gravity waves can become steepened near the mesopause.Key words: Ionosphere (polar ionosphere) · Meteorology and Atmospheric Dynamics (middle atmosphere dynamics) · Radio Science (Interferometry)

scholarly journals Arctic and Antarctic polar mesosphere summer echoes observed with oblique incidence HF radars: analysis using simultaneous MF and VHF radar data

2004 ◽  
Vol 22 (12) ◽  
pp. 4049-4059 ◽  
Author(s):  
T. Ogawa ◽  
S. Nozawa ◽  
M. Tsutsumi ◽  
N. F. Arnold ◽  
N. Nishitani ◽  
...  
Keyword(s):  
Oblique Incidence ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Radar Data ◽  
Hf Radar ◽  
Doppler Velocity ◽  
Vhf Radar ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Mf Radar

Abstract. Polar mesosphere summer echoes (PMSEs) have been well studied using vertical incidence VHF radars at northern high-latitudes. In this paper, two PMSE events detected with the oblique incidence SuperDARN HF radars at Hankasalmi, Finland (62.3° N) and Syowa Station, Antarctica (69.0° S), are analyzed, together with simultaneous VHF and medium-frequency (MF) radar data. Altitude resolutions of the HF radars in the mesosphere and the lower thermosphere are too poor to know exact PMSE altitudes. However, a comparison of Doppler velocity from the HF radar and neutral wind velocity from the MF radar shows that PMSEs at the HF band appeared at altitudes within 80-90km, which are consistent with those from previous vertical incidence HF-VHF radar results. The HF-VHF PMSE occurrences exhibit a semidiurnal behavior, as observed by other researchers. It is found that in one event, PMSEs occurred when westward semidiurnal winds with large amplitude at 85-88km altitudes attained a maximum. When the HF-VHF PMSEs were observed at distances beyond 180km from MF radar sites, the MF radars detected no appreciable signatures of echo enhancement. Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

scholarly journals Aspect sensitivity measurements of polar mesosphere summer echoes using coherent radar imaging

2002 ◽  
Vol 20 (2) ◽  
pp. 213-223 ◽  
Author(s):  
P. B. Chilson ◽  
T.-Y. Yu ◽  
R. D. Palmer ◽  
S. Kirkwood
Keyword(s):  
Middle Atmosphere ◽  
Radar Imaging ◽  
Brightness Distribution ◽  
High Signal ◽  
Vhf Radar ◽  
Radio Science ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Coherent Radar ◽  
Aspect Sensitivity

Abstract. The Esrange VHF radar (ESRAD), located in northern Sweden (67.88° N, 21.10° E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar’s probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to derive estimates of the prevailing three-dimensional wind associated with the observed PMSE. It is shown that regions within the PMSE with enhanced aspect sensitivity have a correspondingly high signal-to-noise ratio (SNR). Although this relationship has been investigated in the past, the present study allows for an estimation of the aspect sensitivity independent of the assumed scattering models and avoids the complications of comparing echo strengths from vertical and off-vertical beams over large horizontal separations, as in the Doppler Beam Swinging (DBS) method. Regions of enhanced aspect sensitivity were additionally shown to correlate with the wave-perturbation induced downward motions of air parcels embedded in the PMSE.Key words. Ionosphere (polar ionosphere) Meteorology and Atmospheric Dynamics (middle atmosphere dynamics) Radio Science (Interferometry)

Frequency domain interferometry of polar mesosphere summer echoes with the EISCAT VHF radar: A case study

Radio Science ◽  
1992 ◽  
Vol 27 (3) ◽  
pp. 417-428 ◽  
Author(s):  
S. J. Franke ◽  
J. Röttger ◽  
C. LaHoz ◽  
C. H. Liu
Keyword(s):  
Frequency Domain ◽  
Vhf Radar ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes

scholarly journals Occurrence frequencies of polar mesosphere summer echoes observed at 69° N during a full solar cycle

2013 ◽  
Vol 11 ◽  
pp. 327-332 ◽  
Author(s):  
R. Latteck ◽  
J. Bremer
Keyword(s):  
Middle Atmosphere ◽  
Wave Radiation ◽  
Signal Power ◽  
Water Vapour Content ◽  
Vhf Radar ◽  
The North ◽  
Initial Stage ◽  
Significance Levels ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes

Abstract. Polar mesosphere summer echoes (PMSE) are strong enhancements of received signal power at very high radar frequencies occurring at altitudes between about 80 and 95 km at polar latitudes during summer. PMSE are caused by inhomogeneities in the electron density of the radar Bragg scale within the plasma of the cold summer mesopause region in the presence of negatively charged ice particles. Thus the occurrence of PMSE contains information about mesospheric temperature and water vapour content but also depends on the ionisation due to solar wave radiation and precipitating high energetic particles. Continuous and homogeneous observations of PMSE have been done on the North-Norwegian island Andøya (69.3° N, 16.0° E) from 1999 until 2008 using the ALWIN VHF radar at 53.5 MHz. In 2009 the Leibniz-Institute of Atmospheric Physics in Kühlungsborn, Germany (IAP) started the installation of the Middle Atmosphere Alomar Radar System (MAARSY) at the same location. The observation of mesospheric echoes could be continued in spring 2010 starting with an initial stage of expansion of MAARSY and is carried out with the completed installation of the radar since May 2011. Since both the ALWIN radar and MAARSY are calibrated, the received echo strength of PMSE from 14 yr of mesospheric observations could be converted to absolute signal power. Occurrence frequencies based on different common thresholds of PMSE echo strength were used for investigations of the solar and geomagnetic control of the PMSE as well as of possible long-term changes. The PMSE are positively correlated with the solar Lyman α radiation and the geomagnetic activity. The occurrence frequencies of the PMSE show slightly positive trends but with marginal significance levels.

scholarly journals Finland HF and Esrange MST radar observations of polar mesosphere summer echoes

2003 ◽  
Vol 21 (4) ◽  
pp. 1047-1055 ◽  
Author(s):  
T. Ogawa ◽  
N. F. Arnold ◽  
S. Kirkwood ◽  
N. Nishitani ◽  
M. Lester
Keyword(s):  
Middle Atmosphere ◽  
Spectral Width ◽  
Hf Radar ◽  
Doppler Velocity ◽  
Short Period ◽  
Mst Radar ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Thermospheric Dynamics ◽  
Atmospheric Gravity

Abstract. Peculiar near range echoes observed in summer with the SuperDARN HF radar in Finland are presented. The echoes were detected at four frequencies of 9, 11, 13 and 15 MHz at slant ranges of 105–250 km for about 100 min. Interferometer measurements indicate that the echoes are returned from 80–100 km altitudes with elevation angles of 20°–60°. Echo power (< 16 dB), Doppler velocity (between –30 and + 30 ms-1) and spectral width (< 60 ms-1) fluctuate with periods of several to 20 min, perhaps due to short–period atmospheric gravity waves. When the HF radar detected the echoes, a vertical incidence MST radar, located at Esrange in Sweden (650 km north of the HF radar site), observed polar mesosphere summer echoes (PMSE) at altitudes of 80–90 km. This fact suggests that the near range HF echoes are PMSE at HF band, although both radars did not probe a common volume. With increasing radar frequency, HF echo ranges are closer to the radar site and echo power becomes weaker. Possible mechanisms to explain these features are discussed.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides; instruments and techniques)

scholarly journals Studies of polar mesosphere summer echoes by VHF radar and rocket probes

1994 ◽  
Vol 14 (9) ◽  
pp. 139-148 ◽  
Author(s):  
U.-P. Hoppe ◽  
T.A. Blix ◽  
E.V. Thrane ◽  
F.-J. Lübken ◽  
J.Y.N. Cho ◽  
...  
Keyword(s):  
Vhf Radar ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes

Implementation of frequency domain interferometry at the SOUSY VHF radar: First results

Radio Science ◽  
1996 ◽  
Vol 31 (2) ◽  
pp. 263-272 ◽  
Author(s):  
Phillip B. Chilson ◽  
Gerhard Schmidt
Keyword(s):  
Frequency Domain ◽  
Vhf Radar ◽  
First Results

scholarly journals Polar mesosphere summer echoes: a comparison of simultaneous observations at three wavelengths

2007 ◽  
Vol 25 (12) ◽  
pp. 2487-2496 ◽  
Author(s):  
E. Belova ◽  
P. Dalin ◽  
S. Kirkwood
Keyword(s):  
Short Interval ◽  
Beam Width ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Theory Model ◽  
Turbulence Theory ◽  
Vhf Radar ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Uhf Radar

Abstract. On 5 July 2005, simultaneous observations of Polar Mesosphere Summer Echoes (PMSE) were made using the EISCAT VHF (224 MHz) and UHF (933 MHz) radars located near Tromsø, Norway and the ALWIN VHF radar (53.5 MHz) situated on Andøya, 120 km SW of the EISCAT site. During the short interval from 12:20 UT until 12:26 UT strong echoes at about 84 km altitude were detected with all three radars. The radar volume reflectivities were found to be 4×10−13 m−1, 1.5×10−14 m−1 and 1.5×10−18 m−1 for the ALWIN, EISCAT-VHF and UHF radars, respectively. We have calculated the reflectivity ratios for each pair of radars and have compared them to ratios obtained from the turbulence-theory model proposed by Hill (1978a). We have tested different values of the turbulent energy dissipation rate ε and Schmidt number Sc, which are free parameters in the model, to try to fit theoretical reflectivity ratios to the experimental ones. No single combination of the parameters ε and Sc could be found to give a good fit. Spectral widths for the EISCAT radars were estimated from the spectra computed from the autocorrelation functions obtained in the experiment. After correction for beam-width broadening, the spectral widths are about 4 m/s for the EISCAT-VHF and 1.5–2 m/s for the UHF radar. However, according to the turbulence theory, the spectral widths in m/s should be the same for both radars. We also tested an incoherent scatter (IS) model developed by Cho et al. (1998), which takes into account the presence of charged aerosols/dust at the summer mesopause. It required very different sizes of particles for the EISCAT-VHF and UHF cases, to be able to fit the experimental spectra with model spectra. This implies that the IS model cannot explain PMSE spectra, at least not for monodisperse distributions of particles.

scholarly journals Coincident measurements of PMSE and NLC above ALOMAR (69° N, 16° E) by radar and lidar from 1999–2008

2010 ◽  
Vol 10 (10) ◽  
pp. 25081-25116 ◽  
Author(s):  
N. Kaifler ◽  
G. Baumgarten ◽  
J. Fiedler ◽  
R. Latteck ◽  
F.-J. Lübken ◽  
...  
Keyword(s):  
Lower Layer ◽  
Occurrence Rate ◽  
Noctilucent Clouds ◽  
Raman Lidar ◽  
Vhf Radar ◽  
Lidar Measurements ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Radar Measurements ◽  
Sublimation Rates

Abstract. Polar Mesosphere Summer Echoes (PMSE) and Noctilucent Clouds (NLC) have been routinely measured at the ALOMAR research facility in Northern Norway (69° N, 16° E) by lidar and radar, respectively. 2900 h of lidar measurements by the ALOMAR Rayleigh/Mie/Raman lidar were combined with almost 18 000 h of radar measurements by the ALWIN VHF radar, all taken during the years 1999 to 2008, to study simultaneous and common-volume observations of both phenomena. PMSE and NLC are known from both theory and observations to be positively linked. We quantify the occurrences of PMSE and/or NLC and relations in altitude, especially with respect to the lower layer boundaries. The PMSE occurrence rate is with 75.3% considerably higher than the NLC occurrence rate of 19.5%. For overlapping PMSE and NLC observations, we confirm the coincidence of the lower boundaries and find a standard deviation of 1.26 km, hinting at very fast sublimation rates. However, 10.1% of all NLC measurements occur without accompanying PMSE. Comparison of occurrence rates with solar zenith angle reveals that NLC without PMSE mostly occur around midnight indicating that the ice particles were invisible to the radar due to the reduced electron density.

scholarly journals Influence of tides and gravity waves on layering processes in the polar summer mesopause region

2008 ◽  
Vol 26 (12) ◽  
pp. 4013-4022 ◽  
Author(s):  
P. Hoffmann ◽  
M. Rapp ◽  
J. Fiedler ◽  
R. Latteck
Keyword(s):  
Gravity Waves ◽  
Lower Layer ◽  
Vhf Radar ◽  
Remarkable Feature ◽  
Ice Cloud ◽  
Radar Echoes ◽  
Layer Structures ◽  
Short Period ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes

Abstract. Polar Mesosphere Summer Echoes (PMSE) have been studied at Andenes (69° N, 16° E), Norway, using VHF radar observations since 1994. One remarkable feature of these observations is the fact that {during 50% of the time,} the radar echoes occur in the form of two or more distinct layers. In the case of multiple PMSE layers, statistical analysis shows that the lower layer occurs at a mean height of ~83.4 km, which is almost identical to the mean height of noctilucent clouds (NLC) derived from observation with the ALOMAR Rayleigh/Mie/Raman lidar at the same site. To investigate the layering processes microphysical model simulations under the influence of tidal and gravity waves were performed. In the presence of long period gravity waves, these model investigations predict an enhanced formation of multiple PMSE layer structures, where the lower layer is a consequence of the occurrence of the largest particles at the bottom of the ice cloud. This explains the coincidence of the lowermost PMSE layers and NLC. During periods with enhanced amplitudes of the semidiurnal tide, the observed NLC and PMSE show pronounced tidal structures comparable to the results of corresponding microphysical simulations. At periods with short period gravity waves there is a tendency for a decreasing occurrence of NLC and for variable weak PMSE structures.

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