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 ◽  
...  

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.

2011 ◽  
Vol 11 (4) ◽  
pp. 1355-1366 ◽  
Author(s):  
N. Kaifler ◽  
G. Baumgarten ◽  
J. Fiedler ◽  
R. Latteck ◽  
F.-J. Lübken ◽  
...  

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 not detected by the radar due to the reduced electron density.


2008 ◽  
Vol 26 (12) ◽  
pp. 4013-4022 ◽  
Author(s):  
P. Hoffmann ◽  
M. Rapp ◽  
J. Fiedler ◽  
R. Latteck

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.


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 ◽  
...  

2021 ◽  
Author(s):  
Michael Gerding ◽  
Gerd Baumgarten ◽  
Franz-Josef Lübken ◽  
Matthias Clahsen ◽  
Marius Zecha

<p>Noctilucent Clouds (NLC) are observed since 1997 by a RMR lidar at a mid-latitude site at Kühlungsborn/Germany (54°N, 12°E). In June 2019, we detected the brightest NLC so far, having a backscatter coefficient at 532 nm of ~50<sup>-10</sup> /m/sr, while 2.5<sup>-10</sup> /m/sr is a typical value at this location. Another three NLC in that period reached a backscatter coefficient of more than 20<sup>-10</sup> /m/sr. These strong NLC allow, e.g., for high-resolved studies with temporal resolution of 10 seconds and vertical resolution of 45 m. We will show examples of high-frequency oscillations in our data that cannot be found with typical integration times of several minutes. The period in June 2019 was not only unique in terms of NLC brightness, but also regarding NLC occurrence. While the all-year average is ~6 %, the occurrence rate in 2019 was 13 % and, and 20% if we consider June only. In the past, we found an anti-correlation between solar activity and NLC occurrence: Increasing solar UV radiation results in enhanced radiative heating and photolytic water vapor destruction. However, the high number of NLC in 2019 can only partly be explained by solar activity, even if the Lyman-alpha flux was slightly lower compared to previous years. TIMED/SABER monthly averaged temperature profiles showed an unusual low mesopause in June 2019, related to lower-than-average temperatures below 83 km. We claim that this as the main reason for the comparatively frequent and bright NLC. At the same time, meridional wind data of our nearby meteor radar show only weak southward winds and even a wind reversal at 93 km, which is not typical for the season. We will discuss potential reasons for the strange dynamical situation. We note that the weather dependent lidar observations are in good agreement with the radar observations of ice particles, so-called Mesospheric Summer Echoes (MSE). Co-located radar observations also showed unusually large occurrence rates of MSE in June 2019 as well as the occasion of many MSE below 83 km altitude.</p>


2008 ◽  
Vol 26 (9) ◽  
pp. 2795-2806 ◽  
Author(s):  
R. Latteck ◽  
W. Singer ◽  
R. J. Morris ◽  
W. K. Hocking ◽  
D. J. Murphy ◽  
...  

Abstract. Polar Mesosphere Summer Echoes (PMSE) have been observed in the high latitudes of the Northern and Southern Hemisphere for several years using VHF radars located at Andenes/Norway (69° N, 16° E), Resolute Bay/Canada (75° N, 95° W), and Davis/Antarctica (69° S, 78° E). The VHF radars at the three sites were calibrated using the same methods (noise source and delayed transmitting signal) and identical equipment. Volume reflectivity was derived from the calibrated echo power and the characteristics of the seasonal variation of PMSE were estimated at the sites for the years 2004 to 2007. The largest peak volume reflectivity of about 2×10−9 m−1 was observed at Andenes compared with their counterparts at Davis (~4×10−11 m−1) and Resolute Bay (~6×10−12 m−1). The peak of the PMSE height distribution is 85.6 km at Davis which is about 1 km higher than at Andenes. At Resolute Bay the height distribution peaks at about 85 km but only a few layers were found below 84 km. The mean PMSE occurrence rate is 83% at Andenes, 38% at Davis with larger variability and only 18% at Resolute Bay (in late summer). The duration of the PMSE season varies at Andenes from 104 to 113 days and at Davis from 88 to 93 days. In general the PMSE seasons starts about 5 days later at Davis and ends about 10 days earlier compared to Andenes. In all three seasons the PMSE occurrence suddenly drops to a much lower level at Davis about 32 days after solstice whereas the PMSE season decays smoothly at Andenes. The duration of the PMSE season at Andenes and Davis is highly correlated with the presence of equatorward directed winds, the observed differences in PMSE occurrence are related to the mesospheric temperatures at both sites.


2007 ◽  
Vol 25 (12) ◽  
pp. 2487-2496 ◽  
Author(s):  
E. Belova ◽  
P. Dalin ◽  
S. Kirkwood

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.


Radio Science ◽  
1992 ◽  
Vol 27 (3) ◽  
pp. 417-428 ◽  
Author(s):  
S. J. Franke ◽  
J. Röttger ◽  
C. LaHoz ◽  
C. H. Liu

2000 ◽  
Vol 18 (12) ◽  
pp. 1599-1612 ◽  
Author(s):  
P. B. Chilson ◽  
S. Kirkwood ◽  
I. Häggström

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)


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