Preliminary Lightning Observations over Greece

Journal of Geophysical Research Atmospheres (Impact Factor: 3.44). 01/2011; DOI: 10.1029/2011JD017063

ABSTRACT Chronis, T.
Preliminary Lightning Observations over Greece
J. Geophys. Res., doi:10.1029/2011JD017063, in press.

(unofficial abstract) Several, PRETTY COOL (if i may add) observations that associate to lightning never (and i mean never) before reported in literature; two words: sea surface salinity and cloud capacitance...

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    ABSTRACT: The effects of finitely conducting ground on the signature of lightning-generated magnetic fields at ground level were evaluated by numerical solution of Sommerfeld's integrals. Results are presented for distances between 10 m to 1 km from the lightning channel and for ground conductivities in the range of 0.01 and 0.0001 S/m. The results obtained from the exact theory are compared with the predictions of two frequently used analytical approximations to Sommerfeld's equations. Based on that comparison, the limits of validity of these approximate theories are obtained.
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    ABSTRACT: Twenty days of lightning activity recorded during winter 2002–2003 in the Mediterranean region with significant rain accumulation in Greece were studied on the basis of the measurements of the UK Met Office long-range VLF sferics Arrival Time Difference (ATD) system and the spaceborne NASA Lightning Imaging Sensor (LIS) sensor onboard the Tropical Rainfall Measurement Mission (TRMM) satellite. Cloud-to-Ground (CG) flash density as well as history of CG activity were investigated on the basis of the sferics fixes. LIS observations were studied to document both intracloud (IC) and CG flashes in terms of extension, duration and development during different TRMM passes over the Mediterranean Sea. The analysis revealed that more than 266,000 CG flashes occurred during the 20 studied days. CG flashes were mostly located over sea, and CG density was found to follow the North African and Turkish shorelines. About 85% of the CG flashes were composed of a single sferics fix while the number of sferics fixes per CG flash was found ranging up to 15. Flash duration was found ranging from a few milliseconds to 2 s on the basis of LIS observations.
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    ABSTRACT: This paper presents a study of the characteristics of lightning activity during the Cyprus low winter storms over the eastern coast of the Mediterranean. The focus is on changes in the nature of thunderstorms crossing the coastline from the sea into the northern and central parts of Israel, as manifested in their electrical activity. It is based on the Lightning Position and Tracking System (LPATS) measurements of lightning ground strikes during four winter seasons between 1995 and 1999. The spatial distribution shows a maximum of lightning ground strikes over Mount Carmel, possibly due to its topographical forcing. The annual variation shows a major maximum in January with two minor peaks, one in November and another in March, which can be explained by changes in the static instability of the atmosphere throughout the rainy period. The average fraction of positive ground flashes was found to be 6% and their average peak current 41 kA. The average peak current of negative ground flashes was 27 kA. Larger frequencies of ground flashes were detected over the sea than over land during the study period. This is probably due to the large heat and humidity fluxes from the sea surface, which destabilize the colder air above and drive cloud convection. The annual distribution shows that during midwinter (December–January– February) there is higher flash density over the sea, while during autumn and spring the flash density is similar above the two regions. The diurnal variation shows that the maximum in maritime lightning activity was at 0500 LST and over land at 1300 LST. The mean peak current of positive ground flashes was higher over land and of negative ground flashes, over the sea.
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