Observations of noctilucent clouds from Lithuania

Dubietis, A.; Dalin, Peter; Balčiūnas, Ričardas; Cernis, K.

doi:10.1016/j.jastp.2010.07.004

Cited by 19 publications

(27 citation statements)

References 36 publications

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“…A slightly positive statistically insignificant trend is derived for Lithuanian data, and a nearly zero trend for Canadian data. All the regression coefficients and their 95% confidence levels as well as phase lag vs. Ly alpha flux are summarized in Figures 1b, 3b, and 4b are caused by different approaches taking into account tropospheric cloudiness as described in detail by Romejko et al (2003) for the Moscow data, Dubietis et al (2010) for the Lithuanian data, and Zalcik et al (2014) for the Canadian data. Nevertheless, in all cases, within the considered time period (1990 to 2013), there was no statistically significant trend in both the weather-corrected NLC number over a season and the weather-corrected NLC brightness.…”

Section: Long-term Ground-based Nlc Observations: Variables Time Sermentioning

confidence: 99%

“…The methodology and data sets of ground-based NLC observations in Moscow (Russia), Vilnius (Lithuania), and La Ronge (Canada) are outlined in papers by Romejko et al (2002), Romejko et al (2003), Dubietis et al (2010), Dubietis et al (2011), andZalcik et al (2014). All three databases were published and discussed previously but never were considered together.…”

Section: Long-term Ground-based Nlc Observations: Variables Time Sermentioning

confidence: 99%

“…However, the different approaches arrived to controversial conclusions on the subject which suggest either continuously increasing NLC numbers over Western Europe (Gadsden 1990(Gadsden , 1998 and PMC activity for sub-polar and polar latitudes (DeLand et al 2006(DeLand et al , 2007Shettle et al 2009) or zero-trends derived from ground-based observations (Romejko et al 2002(Romejko et al , 2003Dalin et al 2006;Kirkwood et al 2008;Dubietis et al 2010). The main reasons for these differences are attributed to different analyzed variables, different time intervals and latitude range used for the analysis and inhomogeneity of the datasets (Dalin et al 2006;Kirkwood et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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Noctilucent clouds observed from the ground: sensitivity to mesospheric parameters and long-term time series

et al. 2014

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Long-term systematic observations of noctilucent clouds in the regions of Moscow (Russia), Vilnius (Lithuania), and La Ronge (Canada) are considered. Variables, describing the seasonal activity of noctilucent clouds, are discussed. It is shown that there are no statistically significant trends within time intervals of several recent decades. This result is compared to other known findings on trends in mesospheric clouds. Based on the data of the modern ground-based noctilucent cloud observing network in the northern hemisphere and simultaneous satellite data on mesospheric temperature and humidity, we estimate sensitivity of noctilucent clouds to the relative humidity of the upper mesosphere. Such an approach allows us to discuss possible changes of the upper-mesospheric relative humidity, which are consistent with a zero secular trend in noctilucent cloud activity.

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Section: Long-term Ground-based Nlc Observations: Variables Time Sermentioning

confidence: 99%

Section: Long-term Ground-based Nlc Observations: Variables Time Sermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Noctilucent clouds observed from the ground: sensitivity to mesospheric parameters and long-term time series

et al. 2014

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“…Indeed, a direct relationship between the NLC occurrence frequency and solar activity is now reliably established. Ample long-term groundbased [16][17][18][19][20] and satellite observations [21,22] revealed that NLC characteristics vary inversely with the solar activity: in general, NLC occurrence frequency and brightness increase in the years of solar minimum, and vice versa. In this regard, another important issue concerns the long-term trends in variability of NLCs.…”

Section: Noctilucent Cloud Formationmentioning

confidence: 99%

Noctilucent clouds: modern ground-based photographic observations by a digital camera network

et al. 2011

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Noctilucent, or "night-shining," clouds (NLCs) are a spectacular optical nighttime phenomenon that is very often neglected in the context of atmospheric optics. This paper gives a brief overview of current understanding of NLCs by providing a simple physical picture of their formation, relevant observational characteristics, and scientific challenges of NLC research. Modern ground-based photographic NLC observations, carried out in the framework of automated digital camera networks around the globe, are outlined. In particular, the obtained results refer to studies of single quasi-stationary waves in the NLC field. These waves exhibit specific propagation properties-high localization, robustness, and long lifetime-that are the essential requisites of solitary waves.

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“…On the other hand, ground-based observations of noctilucent clouds have not been able to discern any significant trend (e.g. Kirkwood et al, 2008a;Dubietis et al, 2010), nor have direct observations of temperature (e.g. Lübken, 2000).…”

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confidence: 99%

Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

et al. 2013

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The relationship between polar mesosphere summer echoes (PMSE) and geomagnetic disturbances (represented by magnetic <I>K</I> indices) is examined. Calibrated PMSE reflectivities for the period May 2006–February 2012 are used from two 52.0/54.5 MHz radars located in Arctic Sweden (68° N, geomagnetic latitude 65°) and at two different sites in Queen Maud Land, Antarctica (73°/72° S, geomagnetic latitudes 62°/63°). In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH) there is a strong increase in mean PMSE reflectivity between quiet and disturbed geomagnetic conditions. Mean volume reflectivities are slightly lower at the SH locations compared to the NH, but the position of the peak in the lognormal distribution of PMSE reflectivities is close to the same at both NH and SH locations, and varies only slightly with magnetic disturbance level. Differences between the sites, and between geomagnetic disturbance levels, are primarily due to differences in the high-reflectivity tail of the distribution. PMSE occurrence rates are essentially the same at both NH and SH locations during most of the PMSE season when a sufficiently low detection threshold is used so that the peak in the lognormal distribution is included. When the local-time dependence of the PMSE response to geomagnetic disturbance level is considered, the response in the NH is found to be immediate at most local times, but delayed by several hours in the afternoon sector and absent in the early evening. At the SH sites, at lower magnetic latitude, there is a delayed response (by several hours) at almost all local times. At the NH (auroral zone) site, the dependence on magnetic disturbance is highest during evening-to-morning hours. At the SH (sub-auroral) sites the response to magnetic disturbance is weaker but persists throughout the day. While the immediate response to magnetic activity can be qualitatively explained by changes in electron density resulting from energetic particle precipitation, the delayed response can largely be explained by changes in nitric oxide concentrations. Observations of nitric oxide concentration at PMSE heights by the Odin satellite support this hypothesis. Sensitivity to geomagnetic disturbances, including nitric oxide produced during these disturbances, can explain previously reported differences between sites in the auroral zone and those at higher or lower magnetic latitudes. The several-day lifetime of nitric oxide can also explain earlier reported discrepancies between high correlations for average conditions (year-by-year PMSE reflectivities and <I>K</I> indices) and low correlations for minute-to-day timescales

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Observations of noctilucent clouds from Lithuania

Cited by 19 publications

References 36 publications

Noctilucent clouds observed from the ground: sensitivity to mesospheric parameters and long-term time series

Noctilucent clouds observed from the ground: sensitivity to mesospheric parameters and long-term time series

Noctilucent clouds: modern ground-based photographic observations by a digital camera network

Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

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