Journal of Geophysical Research: Atmospheres
RESEARCH ARTICLE
10.1029/2018JD028716
Key Points:• Positive PB pulses (the same initialpolarity as the positive return stroke)in 40 +CGs and negative PB pulses in
6 +CGs were located• Positive PB pulses were produced by
upward negative leaders andnegative PB pulses by downward
negative leaders• Negative leaders producing negative
PB pulses in +CGs ﬁrst developed
downward but would move backupward before the return stroke

Supporting Information:• Supporting Information S1
Correspondence to:T. Wu,
tingwu@gifu-u.ac.jp

Citation:
Wu, T., Wang, D., & Takagi, N. (2018).
Locating preliminary breakdown pulses
in positive cloud-to-ground lightning.
Journal of Geophysical Research:
Atmospheres, 123, 7989–7998. https://doi.org/10.1029/2018JD028716
Received 25 MAR 2018
Accepted 24 JUL 2018
Accepted article online 1 AUG 2018
Published online 14 AUG 2018

Locating Preliminary Breakdown Pulses in Positive
Cloud-to-Ground Lightning
Ting Wu1
1, Daohong Wang1, and Nobuyuki Takagi1

Department of Electrical, Electronics and Computer Engineering, Gifu University, Gifu, Japan

Abstract This paper provides the ﬁrst concrete evidence that preliminary breakdown (PB) pulses of either
polarity in positive cloud-to-ground (+CG) lightning are produced by negative leaders. Three-dimensional
location results of PB pulses in 46 +CG ﬂashes are analyzed. The majority (40) of the +CG ﬂashes started
with positive PB pulses (+PBPs), the same polarity as the positive return stroke. Location results showedthat +PBPs were produced by leaders propagating upward, which were determined to be negative leaders
based on PB pulse polarities. Similarly, for the negative PB pulses ( PBPs) found in six +CG ﬂashes,
location results showed that they were produced by leaders propagating downward, and we determinedthat these were also negative leaders. Upward negative leaders producing +PBPs in +CG lightning are very
similar to those in intracloud lightning. They usually propagate upward before turning in a horizontal
direction. Downward negative leaders producing PBPs in +CG lightning are more complicated. They
usually move back upward after a period of downward propagation. Positive leaders could not be
detected, but their possible propagations are analyzed along with possible charge structures for different
types of PB pulses. We also demonstrate that PB pulse studies based on single-site records arepotentially unreliable.

Plain Language Summary Lightning ﬂashes usually start with a train of bipolar pulses called
preliminary breakdown (PB) pulses. In negative cloud-to-ground ( CG) ﬂashes, PB pulses usually havenegative initial polarity, the same as the negative return stroke. However, in +CG ﬂashes, PB pulses with either
polarity have been observed by many studies. PB pulses in +CG ﬂashes are usually explained by the
movement of positive leaders because a positive leader connecting the ground is always necessary for a +CG
ﬂash. In this study, we provide the ﬁrst concrete evidence that PB pulses of both polarities are produced bynegative leaders. Speciﬁcally, positive PB pulses are produced by upward-propagating negative leadersand negative PB pulses are produced by downward-propagating negative leaders. Possible charge structures
for different types of PB pulses in +CG ﬂashes are also discussed.

1. Introduction
On wideband electric ﬁeld change (E-change) waveforms, lightning ﬂashes usually start with a series ofbipolar pulses called preliminary breakdown (PB) pulses or initial breakdown pulses. Numerous studies havebeen devoted to the analysis of PB pulse characteristics (Johari et al., 2016, and references therein). With thedevelopment of low-frequency (LF) lightning locating systems, PB pulses in both negative cloud-to-ground( CG) lightning and intracloud (IC) lightning have been located in three dimensions (3-D), and it is now veryclear that PB pulses in CG lightning and IC lightning are usually produced by negative leaders going
downward and upward, respectively, from a negative charge region (Bitzer et al., 2013; Karunarathne et al.,2013; Wu et al., 2015). However, location results of PB pulses in positive CG (+CG) lightning have not yet beenreported in any study, mainly due to the paucity of +CG ﬂashes.

©2018. American Geophysical Union.
All Rights Reserved.

WU ET AL.

Many studies have found that PB pulses in +CG lightning are much more complicated than those in CG
lightning. While the initial polarity of PB pulses in CG lightning is usually negative (using the physics sign
convention), the same as the negative return stroke, the initial polarity of PB pulses in +CG lightning canbe either positive or negative (Gomes & Cooray, 2004; Johari et al., 2016; Nag & Rakov, 2012; Qie et al.,2013; Schumann et al., 2013; Ushio et al., 1998; Wu et al., 2013; Zhang et al., 2013). To further complicate thisproblem, some studies reported observations of PB pulses with no clear polarity (Gomes & Cooray, 2004; Qieet al., 2013) and multiple pulse trains with opposite polarities (Gomes & Cooray, 2004; Johari et al., 2016;
Zhang et al., 2013).

7989

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

The above studies also propose various theories to explain the physicalprocesses responsible for different types of PB pulses in +CG lightning.
As a positive leader connecting the ground is always a necessary part in
a +CG ﬂash, PB pulses in +CG lightning are usually explained by thedevelopment of a positive leader (Nag & Rakov, 2012; Qie et al., 2013;
Wu et al., 2013). For example, Nag and Rakov (2012) attributed the positive PB pulses (the same polarity as the positive return stroke) to thedownward movement of a positive leader. They also noted that there
was no explanation for PB pulses exhibiting both polarities.

Figure 1. Twelve sites of FALMA during the summer observation of 2017 andlocations of all return strokes produced by 46 positive cloud-to-ground ﬂashes
analyzed in this paper. Black rectangles represent sites of FALMA. The latitude
and longitude of the site at (0, 0) is (35.475°E, 136.960°N). Red pluses represent
positive return strokes. Blue triangles represent negative return strokes.
FALMA = Fast Antenna Lightning Mapping Array.

However, there is accumulating evidence that +CG ﬂashes usually startwith a negative leader going upward similar to IC ﬂashes as revealed by
the Lightning Mapping Array (LMA) (Lu et al., 2009; van der Velde et al.,2014; van der Velde & Montanyà, 2013; Wiens et al., 2005). The positive
leader still exists; according to the bidirectional leader concept (e.g.,
Mazur & Ruhnke, 1993), as the negative leader develops upward, thepositive leader develops simultaneously in the opposite direction.
However, the positive leader usually radiates much more weakly inradio frequencies than the negative leader does and thus cannot beeffectively located on most occasions (e.g., Shao et al., 1999).
Considering the above evidence, it is very likely that PB pulses in +CG
lightning are produced by negative leaders.

In fact, the idea that a +CG ﬂash starts with both positive and negative
leaders and the negative leader produces the PB pulses was suggested by Kawasaki and Mazur (1992) morethan 20 years ago, but this idea seems to have been overlooked by recent research. In this study, we will provide the ﬁrst concrete evidence that PB pulses of both polarities in +CG lightning are produced by negative
leaders based on the 3-D location results of PB pulses in 46 +CG ﬂashes.

2. Observation and Data
Data in this study were obtained with an LF lightning mapping system, the Fast Antenna Lightning Mapping
Array (FALMA) established in Gifu, Japan. During the summer of 2017, FALMA was comprised of 12 fastantenna sites as indicated by the black squares in Figure 1. The fast antenna receives radio waves in the frequency range of about 500 Hz to 500 kHz and has a time constant of about 200 μs. A sampling rate of 25 MS/s
was used in order to achieve a high timing accuracy. The time-of-arrival technique was employed for lightning locating, but we also used waveform correlation to match peaks at different sites, similar to the technique used by Lyu et al. (2014). In order to reduce noise and increase location accuracy, only the frequency
band of 200 to 500 kHz was used for locating. These efforts have signiﬁcantly improved location results overtraditional LF systems. The location accuracy of FALMA in the horizontal direction over the network is estimated to be around 20 m. More details of FALMA can be found in Wu et al. (2018).
A total of 46 +CG ﬂashes are analyzed in this study. These are +CG ﬂashes produced inside or near the
network of FALMA and can be located relatively accurately.
PB pulses in this study are deﬁned as a series of consecutive pulses with the same initial polarity at the beginning of a lightning ﬂash. According to our data, it seems that all lightning ﬂashes start with multiple pulses
with the same initial polarity, and we treat these pulses as PB pulses. This deﬁnition is similar to that in Wu
et al. (2015). Note that location results are needed to identify the beginning of a lightning ﬂash as it happensthat multiple ﬂashes at different locations occur in the same period and produce overlapping waveforms.
Sometimes PB pulses in +CG lightning are weak and precede the return stroke by a long time. As a result, thedata acquisition system, which has a pretrigger time of 100 ms, failed to record these PB pulses. Such records
usually start with small pulses not triggering the system and therefore the beginning of the ﬂash cannot be
determined. These instances are not included in this paper. According to our data, it seems that all +CG
ﬂashes start with PB pulses. Marshall et al. (2014) suggested that all CG ﬂashes start with PB pulses, andwe speculate that it is possible to extend this conclusion to +CG ﬂashes. However, caution is needed as
the deﬁnition of PB pulses may be different in different studies.

WU ET AL.

7990

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Figure 2. A positive cloud-to-ground ﬂash starting with positive preliminary breakdown pulses. Figures 2a and 2b show
sources and E-change waveform up to 180 ms from the initiation of this ﬂash. The ﬁrst source is represented by a black
triangle and the return stroke by a red plus sign. Sources before the return stroke are color coded by the time. Sources after
the return stroke are shown in black. Figures 2c and 2d show sources and E-change waveform during the ﬁrst 10 ms of thisﬂash. DU = digital unit; E-change = electric ﬁeld change.

Of the 46 +CG ﬂashes analyzed in this paper, 36 produced only one positive return stroke. In seven +CG
ﬂashes, two positive return strokes were produced, and always with two different terminations. In the remaining three cases, a positive return stroke was followed by one or more negative return strokes, but in only oneof these three cases the negative return strokes had the same termination as the positive return stroke. A
total of 53 positive return strokes and 6 negative return strokes (with three different terminations) are produced by these +CG ﬂashes. Locations of these return strokes are shown in Figure 1.
The physics sign convention is used in this paper, so a positive return stroke produces a positive E-change
pulse. We will call PB pulses with the initial polarity the same as the positive return stroke positive PB pulses(+PBPs) and those with opposite polarity negative PB pulses ( PBPs). Of the 46 +CG ﬂashes, 40 ﬂashes started
with +PBPs and 6 started with PBPs.
As the fast antennas were not calibrated, the magnitude of E-ﬁeld changes is shown in the digital unit.

3. Results
3.1. Location Results of +PBPs
The majority (40 out of 46) of +CG ﬂashes analyzed in this study started with +PBPs. This is in agreement withprevious studies (Gomes & Cooray, 2004; Nag & Rakov, 2012; Qie et al., 2013; Schumann et al., 2013; Zhang
et al., 2013). Initial leaders producing +PBPs in +CG ﬂashes seem to be very similar. We will provide two examples to illustrate their characteristics.
3.1.1. Example One
Figure 2 shows a typical example of a +CG ﬂash starting with +PBPs. This ﬂash lasted for 527 ms and produced one positive return stroke at 125.1 ms as indicated by the red plus sign in Figure 2. Sources up to

WU ET AL.

7991

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Figure 3. The second example of a positive cloud-to-ground ﬂash starting with positive preliminary breakdown pulses.
Subplots are arranged as in Figure 2. This ﬂash lasts for a short time, and Figures 3a and 3b include all sources of thisﬂash. DU = digital unit; E-change = electric ﬁeld change.

180 ms after the initiation are shown in Figures 2a and 2b, with sources after the return stroke shown in black.
According to the location results in Figures 2a and 2b, we can see this ﬂash started with a leader progressing
upward and then propagating mainly horizontally with several branches, very similar to an IC ﬂash. This isconsistent with +CG observations with the LMA (Lu et al., 2009; van der Velde et al., 2014; van der Velde &Montanyà, 2013; Wiens et al., 2005) and also agrees with many observations that +CG ﬂashes are usuallyaccompanied by IC ﬂashes (Kong et al., 2008; Saba et al., 2009; Shao et al., 1999). From Figure 2b we cansee the negative leader progressed horizontally away from the initiation location for about 10 km when
the positive return stroke was produced near the initiation location. Some sources were located near thelocation of the return stroke from about 10 ms before the return stroke, but no positive leader progressing
downward to the ground could be identiﬁed. After the return stroke, the horizontal negative leader
seemed to continue progressing, as shown by the black sources in Figure 2b.
Figures 2c and 2d show source heights and E-change waveform at the beginning of this ﬂash. A leader going
upward can be clearly seen, which corresponds to +PBPs. We also conﬁrmed that all sites recorded positive
pulses at the beginning (waveforms recorded by all sites are provided as Figure S1 in the supporting information). When the leader turned to the horizontal direction, the pulse polarity started to change and pulses ofboth polarities were recorded. This type of PB is similar to that in IC ﬂashes (Wu et al., 2015). According to thepulse polarity and the leader direction, we determined that the initial upward leader producing +PBPs was anegative leader.
3.1.2. Example Two
The second example of a +CG ﬂash starting with +PBPs is shown in Figure 3. This is a very simple +CG ﬂash
lasting for only about 166 ms. The positive return stroke was produced at 130.9 ms. Processes before thereturn stroke are very similar to those in Figure 2. The initial leader propagated upward and then turned tothe horizontal direction and progressed away from the initiation location. The positive return stroke was

WU ET AL.

7992

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Figure 4. The ﬁrst example of a positive cloud-to-ground ﬂash starting with negative preliminary breakdown pulses.
Subplots are arranged as in Figure 2. DU = digital unit; E-change = electric ﬁeld change.

also produced near the initiation location. However, in this case, no leader development after the returnstroke could be identiﬁed. Sources after the return stroke seemed to be produced at the tips of existing
branches and only lasted for about 35 ms.
Figures 3c and 3d show the sources and E-change waveform during the ﬁrst 16 ms of this ﬂash. Similar to theexample in Figure 2, the initial upward leader produced +PBPs; after the leader turned to the horizontal direction, the pulse polarity started to change. We conﬁrmed that all sites recorded positive pulses at the beginning of this ﬂash (waveforms are provided in Figure S2 in the supporting information). Based on these results,
we determined that the +PBPs in this ﬂash were also produced by an upward negative leader.
3.2. Location Results of

PBPs

Out of 46 +CG ﬂashes analyzed in this paper, only 6 ﬂashes started with PBPs. However, leaders producing
PBPs seem to be more complicated. In this section, we will analyze three examples to demonstrate that
PBPs in +CG ﬂashes are also produced by negative leaders.
3.2.1. Example One
Figure 4 shows the ﬁrst example of a +CG ﬂash starting with PBPs. This +CG ﬂash lasted for 650 ms, and thepositive return stroke was produced at 70.1 ms. Sources up to 98 ms from the initiation are plotted in
Figures 4a and 4b. This ﬂash is outside of the network of FALMA and height results in Figure 4a are scattered,
but we can still see a leader ﬁrst moving downward for a short time and then gradually propagating upward
until the return stroke. Similar to the examples in Figures 2 and 3, the return stroke was produced near the
initiation location. No sources were located near the return stroke. Sources after the return stroke mainly
showed horizontal propagations, and it seems that the existing leader continued progressing after the returnstroke, but with an abrupt change in direction.
Sources and E-change waveform during the initial downward propagation are shown in Figures 3c and 3d. A
downward leader can be identiﬁed and this leader produced PBPs. We also conﬁrmed that all sites

WU ET AL.

7993

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Figure 5. The second example of a positive cloud-to-ground ﬂash starting with negative preliminary breakdown pulses.
Subplots are arranged as in Figure 2. DU = digital unit; E-change = electric ﬁeld change.

recorded negative pulses, which are provided in Figure S3 in the supporting information. Therefore, we
determined that the PBPs in this ﬂash were produced by a downward negative leader.
3.2.2. Example Two
The second example of a +CG ﬂash starting with PBPs is shown in Figure 5. This ﬂash lasted for 1,192 ms.
Sources up to 178 ms after the initiation are shown in Figures 5a and 5b. The positive return stroke was produced at 144.2 ms. Similar to the example in Figure 4, the initial leader in this ﬂash also ﬁrst moved downward
for a short time and then propagated upward. However, in this example, the leader turned to the horizontal
direction more than 100 ms before the return stroke. There were also some scattered sources at a lower layer,from about 4 to 5 km, probably produced by recoil leaders. From Figure 5b, we cannot identify clear channels.
It seems that the initial leader developed into many channels progressing in different directions. However,the positive return stroke was still located near the initiation location.
Figures 5c and 5d show sources and E-change waveform during the ﬁrst 24 ms of this ﬂash. Similar to theexample in Figure 4, we conﬁrmed that during the downward development of the initial leader, all sites
recorded PBPs (provided in Figure S4 in the supporting information), and we determined that the PBPs
in this ﬂash were also produced by a downward negative leader. It is worth noting that from about 20 ms
in Figures 5c and 5d, a train of positive pulses were recorded, which were produced by the negative leader
propagating upward. This explains reports of PB pulses exhibiting both polarities in the literature (Gomes &Cooray, 2004; Johari et al., 2016; Zhang et al., 2013). It also demonstrates that this type of PB pulse results froma negative leader that ﬁrst propagates downward and then propagates upward.
In fact, we do not think it is appropriate to include the second pulse train, which has the opposite polarity to
the ﬁrst pulse train as a PB pulse train. It seems that as long as a leader has mainly vertical movements, it can
produce a train of pulses with the same polarity, similar to PB pulses, but the leader does not necessarily haveany direct connection to the PB.

WU ET AL.

7994

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Figure 6. The third example of a positive cloud-to-ground ﬂash starting with negative preliminary breakdown pulses.
Subplots are arranged as in Figure 2. DU = digital unit; E-change = electric ﬁeld change.

3.2.3. Example Three
Figure 6 shows the third example of a +CG ﬂash starting with PBPs, which differs signiﬁcantly from thetwo examples discussed above. This ﬂash lasted for 660 ms; sources up to 216 ms after the initiation are
shown in Figures 6a and 6b. The positive return stroke was produced at 161.5 ms. The initial leader ﬁrst kept
moving gradually downward for about 80 ms and descended from 6 km to about 2 km. The leader thengradually moved upward to about 7 km before the positive return stroke. From Figure 6b we can see theleader propagated away from the initiation location with several branches for about 20 km. The positive
return stroke was produced near the initiation location and seemed to have no inﬂuence on theleader development.
Figures 6c and 6d show sources and E-change waveform during the ﬁrst 13 ms of this ﬂash. A downward leader producing negative pulses can be identiﬁed, indicating the PBPs in this ﬂash were also produced by adownward negative leader.
The PB pulses in this example were extremely weak and the E-change waveform in Figure 6d was recorded by
the closest site. Waveforms during the ﬁrst 2 ms recorded by all 12 sites are shown in Figure 7. In waveforms
recorded by many sites, PB pulses are hardly recognizable. On the other hand, a large and slow change can berecognized, which was probably produced by a very distant return stroke. This example illustrates the potential problems for PB pulse studies using single-site records. First, PB pulses can be buried in the backgroundnoise, which can lead to the false conclusion that the ﬂash does not start with PB pulses. This problem wasalso pointed out by Marshall et al. (2014). Second, multiple ﬂashes can occur simultaneously at different locations, which may make the PB pulses in some ﬂashes appear complicated or abnormal. We suspect that this is
the possible reason for the PB pulses with irregular initial polarity reported by Gomes and Cooray (2004) andchaotic-type PB pulses reported by Qie et al. (2013). Three more cases of PB pulses accompanied with waveforms produced by other ﬂashes are shown in Figure S5 in the supporting information. These cases all belong
to the 46 +CG ﬂashes analyzed in this study. In other words, PB pulses in at least 4 of 46 ﬂashes cannot be
WU ET AL.

7995

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Figure 7. E-change waveforms of the PB pulses of the positive cloud-to-ground ﬂash in Figure 6 recorded at 12 sites. ThesePB pulses were extremely weak and were not recognized by many sites. Time zero corresponds to the time of the ﬁrst
located source in this ﬂash. The waveform in blue color is also plotted in Figure 6d. The horizontal distance between the ﬁrst
source and each site is indicated by the value of d in each subplot. DU = digital unit; E-change = electric ﬁeld change;
PB = preliminary breakdown.

correctly recognized without detailed location results. This result fully shows the potential unreliability of PB
pulse studies based on single-site records.
3.2.4. The Remaining Three Cases
For the remaining three +CG ﬂashes starting with PBPs, one ﬂash is similar to the ﬁrst example in
Figure 4 and another ﬂash is similar to the third example in Figure 6. For the ﬁnal ﬂash, we found thatthe initial leader producing PBPs propagated downward and thus was a negative leader. After the
downward leader, sources were scattered either because of the inaccuracy in location results or complicated branches. In short, we determined that PBPs in all six +CG ﬂashes were produced by downward
negative leaders.

4. Summary and Discussion
Based on the 3-D location results of PB pulses in 46 +CG ﬂashes, this study determined that these PB pulses
were all produced by negative leaders. Out of 46 +CG ﬂashes analyzed in this paper, 40 ﬂashes started with
+PBPs, which were produced by negative leaders propagating upward. The remaining six ﬂashes started with
PBPs, which were produced by negative leaders propagating downward.
Although the possibility that PB pulses in +CG ﬂashes are produced by negative leaders has been rarely
mentioned in previous studies, it is actually an expected result. It is well-known that positive leaders usuallydevelop continuously while negative leaders are stepped. In CG and IC ﬂashes, PB pulses were observed
to correspond to light bursts of negative initial leaders (Stolzenburg et al., 2013), indicating that PB pulses
were produced by the stepping of negative leaders. In +CG ﬂashes, other than the positive initial leaderswhich later contact the ground, there are also negative initial leaders according to the bidirectional

WU ET AL.

7996

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

leader concept (e.g., Mazur & Ruhnke, 1993) and LMA observations (van der Velde et al., 2014). It is a natural
result that PB pulses in +CG ﬂashes are produced by the negative initial leaders rather than the positive
initial leaders.
The +PBPs in +CG ﬂashes are very similar to those in IC ﬂashes, both of which are produced by upwardmoving negative leaders. However, there are also some differences. In the case of IC ﬂashes, the positive leader usually propagates horizontally when the negative leader develops upward. The positive leader usuallycannot be directly detected but can be inferred from the sources of recoil leaders traversing the positive leader channels. To demonstrate that our system can readily detect sources from recoil leaders, an example ofan IC ﬂash is shown in Figure S6 in the supporting information. In the case of +CG ﬂashes starting with +PBPs,
it seems that no sources from recoil leaders can be detected, as can be seen from the examples in Figures 2
and 3. These examples indicate that the positive leader does not have much interaction with negative
charges. Therefore, the possible charge structure for +PBPs in +CG ﬂashes is a relatively small negative charge
region below a larger positive charge region, and these +CG ﬂashes are initiated between these two charge
regions. This result is consistent with the report of the presence of a lower negative charge region in thunderstorms producing +CG ﬂashes (Rust et al., 2005; Wiens et al., 2005).
Only six +CG ﬂashes started with PBPs. We determined that PBPs were produced by downward negative
leaders, but the behavior of these negative leaders was more complicated. It is somewhat difﬁcult to imagine
a +CG ﬂash starting with a downward negative leader because the necessary component for a +CG ﬂash is a
downward positive leader. However, as demonstrated in section 3.2, the downward negative leader always
returns upward before the positive return stroke, so the positive leader may ﬁrst move upward or horizontallyfor a short period before turning downward to the ground. The problem then is determining what kind of
charge structure can produce these types of positive and negative leaders. Considering the fact that
PBPs in +CG ﬂashes are relatively rare, the responsible charge structure should also be rare. It may include
horizontally stacked positive and negative charge regions. The negative leader ﬁrst develops downward fromthe negative charge region. After moving horizontally for a while, it may get to a location below a positive
charge region and then move upward. The positive leader may ﬁrst develop in the negative charge region
in the horizontal or upward direction. Later it is possible to progress out of the negative charge region andturn to the ground.
The above analyses are speculation. Further studies on the charge structure producing different types of PB
pulses are certainly needed. In our future study, we will include all IC ﬂashes and CG ﬂashes produced in thesame thunderstorm as +CG ﬂashes and analyze the thunderstorm charge structure responsible for different
types of PB pulses in +CG ﬂashes.
Acknowledgments
This work was supported by the Ministryof Education, Culture, Sports, Science,
and Technology of Japan (grants
15H02597, 16H04315 and 18K13618).
Location results of +CG ﬂashes reported
in this paper can be downloaded at
http://doi.org/10.5281/zenodo.1205782.
More information of FALMA and more
examples of lightning ﬂashes imaged by
FALMA can be found at https://www1.
gifu-u.ac.jp/~lrg/falma.html.

WU ET AL.

References
Bitzer, P. M., Christian, H. J., Stewart, M., Burchﬁeld, J., Podgorny, S., Corredor, D., et al. (2013). Characterization and applications of VLF/LF
source locations from lightning using the Huntsville Alabama Marx Meter Array. Journal of Geophysical Research: Atmospheres, 118,
3120–3138. https://doi.org/10.1002/jgrd.50271
Gomes, C., & Cooray, V. (2004). Radiation ﬁeld pulses associated with the initiation of positive cloud to ground lightning ﬂashes. Journal of
Atmospheric and Solar: Terrestrial Physics, 66(12), 1047–1055. https://doi.org/10.1016/j.jastp.2004.03.015
Johari, D., Cooray, V., Rahman, M., Hettiarachchi, P., & Ismail, M. M. (2016). Characteristics of preliminary breakdown pulses in positive ground
ﬂashes during summer thunderstorms in Sweden. Atmosphere, 7(3), 39. https://doi.org/10.3390/atmos7030039
Karunarathne, S., Marshall, T. C., Stolzenburg, M., Karunarathna, N., Vickers, L. E., Warner, T. A., & Orville, R. E. (2013). Locating initial breakdown
pulses using electric ﬁeld change network. Journal of Geophysical Research: Atmospheres, 118, 7129–7141. https://doi.org/10.1002/
jgrd.50441
Kawasaki, Z.-I., & Mazur, V. (1992). Common physical processes in natural and triggered lightning in winter storms in Japan. Journal ofGeophysical Research, 97(D12), 12,935–12,945. https://doi.org/10.1029/92JD01255
Kong, X., Qie, X., & Zhao, Y. (2008). Characteristics of downward leader in a positive cloud-to-ground lightning ﬂash observed by high-speed
video camera and electric ﬁeld changes. Geophysical Research Letters, 35, L05816. https://doi.org/10.1029/2007GL032764
Lu, G., Cummer, S. A., Li, J., Han, F., Blakeslee, R. J., & Christian, H. J. (2009). Charge transfer and in-cloud structure of large-charge-moment
positive lightning strokes in a mesoscale convective system. Geophysical Research Letters, 36, L15805. https://doi.org/10.1029/
2009GL038880
Lyu, F., Cummer, S. A., Solanki, R., Weinert, J., McTague, L., Katko, A., et al. (2014). A low-frequency near-ﬁeld interferometric-TOA 3-D
Lightning Mapping Array. Geophysical Research Letters, 41, 7777–7784. https://doi.org/10.1002/2014GL061963
Marshall, T., Schulz, W., Karunarathna, N., Karunarathne, S., Stolzenburg, M., Vergeiner, C., & Warner, T. (2014). On the percentage of lightning
ﬂashes that begin with initial breakdown pulses. Journal of Geophysical Research: Atmospheres, 119, 445–460. https://doi.org/10.1002/
2013JD020854
Mazur, V., & Ruhnke, L. H. (1993). Common physical processes in natural and artiﬁcially triggered lightning. Journal of Geophysical Research,98(D7), 12,913–12,930. https://doi.org/10.1029/93JD00626

7997

Journal of Geophysical Research: Atmospheres

10.1029/2018JD028716

Nag, A., & Rakov, V. A. (2012). Positive lightning: An overview, new observations, and inferences. Journal of Geophysical Research, 117,
D08109. https://doi.org/10.1029/2012JD017545
Qie, X., Wang, Z., Wang, D., Liu, M., & Xuan, Y. (2013). Characteristics of positive cloud-to-ground lightning in Da Hinggan Ling forest region at
relatively high latitude, northeastern China. Journal of Geophysical Research: Atmospheres, 118, 13,393–13,404. https://doi.org/10.1002/
2013JD020093
Rust, W. D., MacGorman, D. R., Bruning, E. C., Weiss, S. A., Krehbiel, P. R., Thomas, R. J., et al. (2005). Inverted-polarity electrical structures inthunderstorms in the Severe Thunderstorm Electriﬁcation and Precipitation Study (STEPS). Atmospheric Research, 76(1-4), 247–271.
https://doi.org/10.1016/j.atmosres.2004.11.029
Saba, M. M. F., Campos, L. Z. S., Krider, E. P., & Pinto, O. Jr. (2009). High-speed video observations of positive ground ﬂashes produced byintracloud lightning. Geophysical Research Letters, 36, L12811. https://doi.org/10.1029/2009GL038791
Schumann, C., Saba, M. M. F., Da Silva, R. B. G., & Schulz, W. (2013). Electric ﬁelds changes produced by positives cloud-to-ground lightning
ﬂashes. Journal of Atmospheric and Solar: Terrestrial Physics, 92, 37–42. https://doi.org/10.1016/j.jastp.2012.09.008
Shao, X. M., Rhodes, C. T., & Holden, D. N. (1999). RF radiation observations of positive cloud-to-ground ﬂashes. Journal of GeophysicalResearch, 104(D8), 9601–9608. https://doi.org/10.1029/1999JD900036
Stolzenburg, M., Marshall, T. C., Karunarathne, S., Karunarathna, N., Vickers, L. E., Warner, T. A., et al. (2013). Luminosity of initial breakdown inlightning. Journal of Geophysical Research: Atmospheres, 118, 2918–2937. https://doi.org/10.1002/jgrd.50276
Ushio, T., Kawasaki, Z.-I., Matsu-ura, K., & Wang, D. (1998). Electric ﬁelds of initial breakdown in positive ground ﬂash. Journal of GeophysicalResearch, 103(D12), 14,135–14,139. https://doi.org/10.1029/97JD01975
van der Velde, O. A., & Montanyà, J. (2013). Asymmetries in bidirectional leader development of lightning ﬂashes. Journal of GeophysicalResearch: Atmospheres, 118, 13,504–13,519. https://doi.org/10.1002/2013JD020257
van der Velde, O. A., Montanyà, J., Soula, S., Pineda, N., & Mlynarczyk, J. (2014). Bidirectional leader development in sprite-producing positive
cloud-to-ground ﬂashes: Origins and characteristics of positive and negative leaders. Journal of Geophysical Research: Atmospheres, 119,
12,755–12,779. https://doi.org/10.1002/2013JD021291
Wiens, K. C., Rutledge, S. A., & Tessendorf, S. A. (2005). The 29 June 2000 supercell observed during STEPS. Part II: Lightning and charge
structure. Journal of the Atmospheric Sciences, 62(12), 4151–4177. https://doi.org/10.1175/JAS3615.1
Wu, T., Takayanagi, Y., Funaki, T., Yoshida, S., Ushio, T., Kawasaki, Z.-I., et al. (2013). Preliminary breakdown pulses of cloud-to-ground lightning
in winter thunderstorms in Japan. Journal of Atmospheric and Solar: Terrestrial Physics, 102, 91–98. https://doi.org/10.1016/j.
jastp.2013.05.014
Wu, T., Wang, D., & Takagi, N. (2018). Lightning mapping with an array of fast antennas. Geophysical Research Letters, 45, 3698–3705.
https://doi.org/10.1002/2018GL077628
Wu, T., Yoshida, S., Akiyama, Y., Stock, M., Ushio, T., & Kawasaki, Z. (2015). Preliminary breakdown of intracloud lightning: Initiation altitude,
propagation speed, pulse train characteristics, and step length estimation. Journal of Geophysical Research: Atmospheres, 120, 9071–9086.
https://doi.org/10.1002/2015JD023546
Zhang, Y., Zhang, Y., Lü, W., & Zheng, D. (2013). Analysis and comparison of initial breakdown pulses for positive cloud-to-ground ﬂashes
observed in Beijing and Guangzhou. Atmospheric Research, 129-130, 34–41. https://doi.org/10.1016/j.atmosres.2013.03.006

WU ET AL.

7998