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| Titel |
Comparison of LINET and LIS Lightning Characteristics |
| VerfasserIn |
Hartmut Höller, Hans-Dieter Betz, Kersten Schmidt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037809
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| Zusammenfassung |
| Lightning causes different kinds of emissions along the electromagnetic spectrum. In this
study we compare the long wave sferics emissions in the VLF/LF band as measured by
LINET (Lightning Location Network) to the optical emissions at 777 nm as detected by
the LIS (Lightning Imaging Sensor) aboard the TRMM satellite. LINET detects
the impulsive radiation connected to strokes from intra-cloud (IC) as well from
cloud-to-ground (CG) activity. These emissions can be attributed to predominantly vertically
oriented channels with sufficiently large electric currents. Optical emission can be
connected to these channels as well to a many other components of a flash not seen in
VLF/LF.
Studying the relations between radio wave and optical emissions by lightning is of large
interest not only for general understanding of lightning processes but also with respect to
future applications of planned lightning detectors operating from space. As for some other
satellites, an optical lightning detector is foreseen to be part of the MTG (Meteosat Third
Generation) payload. The sensor will work similar to the LIS sensor which is in low earth
orbit over the tropics and thus can only provide 90 sec snapshots of the lightning history from
an individual thunderstorm.
The present study investigates data obtained from a series of field campaigns performed
with the DLR 6-stations LINET system during TROCCINOX in Brazil (Jan/Feb 2005),
SCOUT-O3 and TWP-ICE in Northern Australia (Nov 2005 - Feb 2006) and AMMA in
W-Africa (June-Nov 2006). In total from all the observations there were around 150 LIS
overpasses of the respective wider LINET network areas during lightning activity. The
LINET data have been restricted to those observed during LIS view time and then have been
clustered into flashes.
It was found that in many cases a LINET stroke was directly followed in time by a LIS
group which was recorded within 2 ms after the stroke. This delay can only partly be
attributed to the scattering processes of light within the thunderstorm, but is otherwise
due to the limited LIS sampling rate which is determined by the 2 ms integration
time of the CCD array. The inter-stroke optical activity is of a much more irregular
nature, thus statistical representation will be adequate. The coincident events did
not show strong correlations between LINET stroke peak current and LIS group
radiance. As LINET can discriminate CG and IC strokes and can also indicate IC
stroke height, a stratification of the data along these categories was performed. The
statements made above for the overall sample did not show distinctive differences in
these categories. This indicates that also CG strokes might produce enough optical
radiation at cloud top, possibly due to large enough in-cloud channel extension. |
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