2004

Diendorfer, G., H. Pichler:
Properties of lighting discharges to an instrumented tower and their implication on the location of those flashes by lightning location systems

International Workshop on Physics of Lightning (IWPL), Guadeloupe, Caribbean, 2004

Since 1998 direct lighting strikes to a radio tower are measured at Gaisberg, a mountain next to the City of Salzburg in Austria. During the period 2000 - 2003 we recorded 129 negative flashes containing 723 strokes with amplitudes greater than 2 kA. From these 129 negative flashes 114 were detected by the LLS (88% FDE). Overall stroke detection efficiency (SDE) - typically lower than FDE - was determined with 68%. For the subset of ß-strokes, which are assumed to be most similar to subsequent strokes in downward flashes we observed a SDE of 81%.

Locations given by the LLS have a mean location error of 450 m. For the correlation of peak currents provided by the LLS and measured directly at the tower we have determined a regression line I_ALDIS = 1.07*I_GB for a-strokes and I_ALDIS = 1.02 * I_GB for ß-strokes.

PDF File (348 KB)

Pichler, H., G. Diendorfer, M. Mair:
Statistics of Lightning Current Parameters Measured at the Gaisberg Tower

18th International Lightning Detection Conference (ILDC), Helsinki, Finland, 2004

201 lightning flashes with a total of 1015 strokes were recorded at the Gaisberg tower from January 2000 to September 2002. From these 201 recorded flashes 62 (31%) did not show any impulse current superimposed on or following the initial continuing current (ICC) being typical for upward initiated lighting.

From the remaining 139 events showing pronounced current pulses, 129 flashes were classified as upward discharges, 10 as downward flashes. This classification is based on the measured lightning channel current prior to the first stroke current pulse. Unfortunately video images showing the direction of channel branching are not available for many events due to bad visibility. The classification from the current flow only may be questionable in some cases.

In the presentation we will show cumulative frequency distributions for the different lightning current parameters as total charge (see Fig) and impulse charge (Q), peak current (Ip), specific energy (W/R) and current steepness (di/dt). The statistical analysis is done separately for the so called a -pulses (superimposed on the ICC) and ß-pulses (following a period of no current in the lightning channel).

In the contribution we will also discuss the differences and similarities to published current parameters measured at other elevated objects as the CN tower or the Peissenberg tower.

PDF File (275 KB)

Schulz, W., G. Diendorfer:
Lightning Peak Currents Measured on Tall Towers and Measured with Lightning Location Systems

18th International Lightning Detection Conference (ILDC), Helsinki, Finland, 2004

Recently Diendorfer et al. [2002] compared lightning peak currents measured at the Gaisberg tower with correlated lightning peak currents reported by the Austrian lightning location system ALDIS. They found a surprisingly good agreement between the measurements at the tower and the amplitudes reported by the lightning location system (LLS).

There are several factors which might influence the relation between the directly measured current at the tower and the current reported by the LLS. The effect of the striking object height and the field attenuation are the key elements for a comparison between the two current values. In this paper we will show the possible range of influence for some of the most important parameters.

PDF File (171 KB)

Heidler, F., G. Diendorfer, W. Zischank:
Examples of severe destruction of trees caused by lightning

27th International Conference on Lightning Protection (ICLP), Avignon, France, 2004

The paper presents two examples of trees severely damaged by lightning strikes. The trees literally burst, when the lightning current passed through the trunk. Huge fragments were blasted away from the trunk and the roots, over distances of several tens of meters. The bursts even caused considerable damage in the surroundings, e.g. removing large patches of bark from nearby trees, when hit by fragments at high speed. The data of lightning location systems revealed that the trees were most likely struck by high amplitude positive cloud-to-ground lightning.

PDF File (1,6 MB)

Schulz, W. and G. Diendorfer:
Performance Improvement of the German Lightning Location System during the 11 Years of Operation

27th  International Conference on Lightning Protection (ICLP), Avignon, France, 2004

The German lightning location system (LLS) BLIDS (BLitz Informations Dienst von Siemens) is now in service for more than 11 years. During this time the system was improved several times. In this paper we are showing the effect of the performance improvements of the system by evaluating some lightning parameters given by the system during the individual years.

PDF File (168 KB)

Schulz, W. and G. Diendorfer:
Lightning field peaks radiated by lightning to tall towers

International Conference on Grounding and Earthing and 1st International Conference on Lightning Physics and Effects (Ground/LPE), Belo Horizonte, Brazil, 2004

Recently Diendorfer et al. [2002] compared lightning peak currents measured at the Gaisberg tower with correlated lightning peak currents reported by the Austrian lightning location system ALDIS. They found a surprisingly good agreement between the measurements at the tower and the peak currents reported by the lightning location system (LLS).

These lightning strikes to the tower radiate higher field peaks due to the presence of two current wavefronts traveling in opposite directions when an elevated object is struck by lightning [Diendorfer and Uman, 1990]. Therefore also the peak currents reported by the LLS should be enhanced compared to lightning to flat ground.

In this paper we will show the reason why there is no significant enhancement in the LLS data. We will do this with the aid of a return stroke model for field calculation and taking into account finite ground conductivity along the propagation path. In addition the limited sensor bandwidth affects the value of measured peak field and therefore the inferred peak current of the strokes.

PDF File (163 KB)

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