A comparative study of negative cloud‐to‐ground lightning characteristics in São Paulo (Brazil) and Arizona (United States) based on high‐speed video observations

Abstract

[1] There are only a few prior reports that detail accurate measurements of the number of strokes in natural negative cloud-to-ground (CG) lightning flashes. These are known as "accurate-stroke-count" studies, and they have been performed using various instruments and techniques. Here, we will examine the lightning characteristics produced by warm-season thunderstorms in two different climate regimes (southern Arizona, United States, and São Paulo, Brazil) using the same instrumentation. The lightning parameters were obtained from high-speed video recordings and time-correlated data provided by lightning locating systems (LLS). The use of these instruments has allowed us to measure the number of strokes in each flash and their polarity, the interstroke intervals, the number of different ground contacts, and the durations of the continuing currents. Altogether 209 negative flashes were recorded on video in the United States and 223 in Brazil (containing a total of 1681 strokes), and the majority of these flashes had at least one stroke reported by a LLS. Statistical analyses of these data sets as a whole did not show any significant differences in the characteristics of negative CG flashes from warm-season thunderstorms in both locations. The mean values for all data are as follows: video multiplicity, 3.9; single-stroke flashes, 19.5%; flash duration, 226.5 ms; interstroke interval, 61.5 ms; long continuing current, 17.5%; multigrounded flashes, 49.5%. Those characteristics were very similar to the well-accepted values for negative flashes in other regions. However, there were large storm-to-storm variations.

The European lightning location system EUCLID – Part 2: Observations

“…This is an underestimation when compared to ground truth recordings. For instance, based on ground truth recordings in Belgium, Poelman et al (2013a) found a mean multiplicity for negative flashes of 3.7, while similar multiplicities are found in comparable ground truth studies at different regions (Rakov and Huffines, 2003;Saraiva et al, 2010;Ballarotti et al, 2012). Likewise, the high percentage of single stroke negative flashes is an overestimation with respect to ground truth observations, reporting in general values between 20 and 40 % (Fleenor et al, 2009;Biagi et al, 2007;Poelman et al, 2013a).…”

Geographical variations of negative cloud-to-ground lightning parameters: A review

“…The results suggest that the CC average intensity in Brazil is larger than in United States, although more data at other locations are necessary before a definitive conclusion. Figures 7 and 8 show recent results about the duration of the CC obtained in Arizona and Sao Paulo [16], inferred from the duration of the channel luminosity following the return stroke obtained by high speed camera observations using a same camera. Figure 7 shows the distributions of duration for short Cc.…”

“…The flash multiplicity of negative flashes was recently studied by Saraiva et al [16] in Arizona (United States) and Sao Paulo (Brazil) using a same high speed camera. Figure 2 compares the num ber of strokes per flash in Arizona and Sao Paulo.…”

“…However, more recently, Saraiva [15] have showed that when the multiplicity data are sorted by different stonn types in the observations in Arizona and Sao Paulo in [16], a clear storm-to-storm lightning parameter vanatlOn is observed in both places, in agreement with past observations in Russia [23]. Data from lightning location system observations in Austria [24] and United States [5,25,26] and from a slow rotating streak-camera array in United States [27] also suggest significant varIatIOn of this parameter for different thunderstorms.…”

“…Observations of interstroke interval for negative flashes in different regions using an accurate technique have been published recently [15,16]. The measurements were done by a high speed camera including 1210 inter stroke intervals observed in Arizona and Sao Paulo.…”