Article

Preliminary Lightning Observations over Greece

Journal of Geophysical Research Atmospheres (Impact Factor: 3.43). 01/2011; 117(D3). DOI: 10.1029/2011JD017063

ABSTRACT

The first Precision Lightning Network, monitoring the Cloud-to-Ground (CG) lightning stroke activity over Greece and surrounding waters is operated and maintained by the Hellenic National Meteorological Service. This paper studies the regional (land/water interface), seasonal and diurnal variability of the CG strokes as a function of density, polarity and peak current. Additional investigation uniquely links the CG stroke current to sea surface salinity and cloud electrical capacitance. In brief, this study's major findings area as follows: (1) The seasonal maps of thunder days agree well with the regional climatic convective characteristics of the study area, (2) the CG diurnal variability is consistent with the global lightning activity observations over land and ocean, (3) the maxima of monthly averaged CG counts are located over land and water during typical summer and fall months respectively for both polarities, (4) CG peak currents show a distinct seasonality with larger currents during relatively colder months and smaller currents during summer months, and (5) strong linear trends between -CGs and sea surface salinity; (6) this trend is absent for +CGs data analysis of the employed database relate to the thunderstorm's RC constant and agrees with previous numerical modeling studies.

    • "1b. Chronis (2012) found stroke density ranging between 0.33 and 10 for the region of Greece and the adjacent sea using data from a Precision Lightning Network (PLN), which detects approximately 95% of the overall CG activity. This difference can be attributed to the fact that the author analysed only one year of data but mainly to the fact that the PLN is a local system and suffers less by underdetection than the long-range detection systems. "
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    ABSTRACT: Lightning activity is analysed in a sector covering the Eastern Mediterranean (16–32°E, 34–46°N) for the years 2005–2014. The study is based on the use of cloud-to-ground (CG) lightning activity data retrieved from ZEUS system, operated by the National Observatory of Athens, and examines the seasonal, diurnal and spatial variability of the lightning activity. The effect of elevation, terrain slope, vegetation cover and convective available potential energy (CAPE) on the distribution of the CG lightning strokes is also investigated. Lightning is modulated by the diurnal cycle of insolation and the underlying topographic features of the region. The lightning strokes are more numerous over the mainland than over the sea. CG lightning activity is dominant over the land and the coastal areas during spring and summer while during the coldest period of the year it is dominant over the sea. The maximum value of lightning activity is observed in June and mostly in the afternoon. The orography and the terrain slope affect the distribution of lightning. During the warmest period of the year, the forested areas have an increased “lightning yield”. The number of CG lightning strokes increases with increasing CAPE and the high correlation between them indicates that CAPE values could be used as a proxy for the presence of lightning activity, at least over the eastern Mediterranean region.
    No preview · Article · Jul 2015 · Atmospheric Research
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    • "In the subject of lightning, their main parameters as well as the process of their development from the leader stroke to the return stroke, including possible multiplicity, are presented in several works [8] [9]; as well, a large observational evidence exist about the connection between lightning and tornadoes, such as summarized in Price[10]where it was tornadoes are associated with certain lightning signatures, in particular with a " jump " in total lightning (IC + CG) few minutes before tornado touchdown and a shift in the CG lightning polarity to a positive one around the time of tornado sightings. The prevalence of the otherwise relatively rare positive cloud to ground lightning flashes (+CG) around the time of tornado formation or touchdown is especially relevant because +CG carry on average one order of magnitude larger electric currents than their negative counterparts (- CG) with peak currents up to more than 200kA[9] [11] [12]. "
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    ABSTRACT: Whereas the basic physical mechanisms leading to the onset and evolution of tornadoes have been well established, some progress can still be useful to identify the conditions supporting the development of a tornado towards a violent or catastrophic stage, as well as possible specific and observable events triggering the onset of a tornado in a generally favorable atmospheric environment. On the basis of an assumed global anisotropy of the physical spaceand the associated non-gauge byuon theory, an additional mechanism of energy accumulation in the process of development of a tornado to its mature stage is proposedand its consistency is checked against a dataset of individual tornadoes as well as of tornado outbreaks. The results point to a significant link between the angle formed by the cosmological vector potentialrepresenting the global anisotropy of the physical space and the surface tangent to the local Earth’s surface and the occurrence of the most energetic tornadoes; as a consequence, such tornadoes are shown to occur only at specific times of the day depending on latitude, longitude and day of the year. Moreover, a further additional mechanism is proposed for the early origin of a tornado, on the basis of the interaction of a large peak current lightning discharge with the cosmological vector potential introduced by the byuon theory. It is shown how, in the framework of the proposed theory, a fraction of the energy of a tornado at its onset stage can originate from the self-energy associated with the formation of the physical space of elementary particles located along the lightning discharge. The verification of the proposed mechanism for the onset of tornadoes is delayed to later time when suitable data sets will be available.
    Full-text · Article · Apr 2014
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    • "In the subject of lightning, their main parameters as well as the process of their development from the leader stroke to the return stroke, including possible multiplicity, are presented in several works [8] [9]; as well, a large observational evidence exist about the connection between lightning and tornadoes, such as summarized in Price[10]where it was tornadoes are associated with certain lightning signatures, in particular with a " jump " in total lightning (IC + CG) few minutes before tornado touchdown and a shift in the CG lightning polarity to a positive one around the time of tornado sightings. The prevalence of the otherwise relatively rare positive cloud to ground lightning flashes (+CG) around the time of tornado formation or touchdown is especially relevant because +CG carry on average one order of magnitude larger electric currents than their negative counterparts (- CG) with peak currents up to more than 200kA[9] [11] [12]. "

    Full-text · Article · Jan 2013
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