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The Meteorological
Society of
Japan
Scientific Online Letters on the Atmosphere (SOLA)
EARLY ONLINE RELEASE
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and accepted for publication. As the article has not yet been
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version may be different from the early online release.
This pre-publication manuscript may be downloaded,
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Commons Attribution 4.0 International (CC BY 4.0) license.
It may be cited using the DOI below.
The DOI for this manuscript is
DOI: 10.2151/sola. 2021-034.
J-STAGE Advance published date: Oct. 4, 2021
The final manuscript after publication will replace the
preliminary version at the above DOI once it is available.SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 1 Analysis of the Tornadic Debris Signatures of the Ichihara 2 Tornado in a Typhoon Environment Using Two Operational 3 C-band Dual-Polarization Weather Radars 4 Akihito Umehara1, Toru Adachi1, Wataru Mahiko1, and Hiroshi Yamauchi2 5 1 Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan 6 2 Japan Meteorological Agency, Tokyo, Japan 7 Corresponding author: Akihito Umehara, Meteorological Research Institute, Japan 8 Meteorological Agency, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan. E-mail: 9 a.umehara@mri-jma.go.jp 10 11 Abstract 12 The tornadic debris signatures (TDSs) of the Ichihara Tornado associated with Typhoon 13 Hagibis (2019) were observed using two operational C-band dual-polarimetric weather 14 radars and an X-band phased-array weather radar (PAWR). This TDS observation was the 15 first to be made over Japan in a typhoon environment. The TDS bins spread over time, 16 and the maximum vertical and aerial extents reached 2.4 km and 9.41 km2, respectively. 17 The estimated rise velocity of the TDS was 8 m·s−1. The first TDS was detected ~1 min 18 before damage reporting began. The TDSs became clearer along with the rotational 19 velocity of the near-surface vortex detected by PAWR. The copolar correlation coefficient 20 reached a minimum (0.27) ~1 min after the tornado passed the most severely damaged 21 area and increased gradually over 4 min. This suggests that heavy and/or dense debris
2 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 was lofted and immediately fell out and/or diffused, whereas light debris remained aloft 2 for ≥4 min. By comparing the PAWR-detected vortex signatures with aerial photographs, 3 we inferred that the first TDS comprised vegetated debris, the clearest TDS mainly 4 comprised destroyed manmade structures. These results indicate that TDS detection is 5 effective both for investigating damage and for recognizing tornado’s occurrence even in 6 a typhoon environment. 7 8 1. Introduction 9 Dual-polarization weather radars derive polarimetric variables from the scatter 10 characteristics of the target. The debris lofted by tornadoes is uniquely characterized by 11 random orientations, irregular shapes, and a wide range of dielectric constants and size 12 distributions. The polarimetric variables have a unique signature—called a “tornadic 13 debris signature” (TDS)—which was originally identified by Ryzhkov et al. (2005). 14 Although various TDS criteria have been proposed (e.g., Ryzhkov et al. 2005; Schultz 15 et al. 2012; Bodine et al. 2013; Van Den Broeke and Jauernic, 2014), a TDS typically 16 presents a moderate-to-high horizontal radar-reflectivity factor (ZHH), a near-zero or low 17 differential reflectivity (ZDR), and a very low copolar cross-correlation coefficient (ρHV), 18 which are co-located with the vortex pattern and hook echo. The specific values are 19 presented in Section 3.1. 20 Previous studies of TDSs included various statistical investigations (e.g., Bodine et a l. 21 2013; Van Den Broeke and Jauernic 2014; Van Den Broeke 2015). Bodine et al. (2013) 22 demonstrated the existence of a proportional relationship between the enhanced Fujita 23 (EF) scale rating and the maximum height of a TDS. Van Den Broeke and Jauernic (2014)
SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 3
1 investigated the relationships between the TDS parameters, EF rating, and land cover for
2 a large number of cases and confirmed Bodine et al.’s (2013) hypothesis that EF ratings
3 are related to the TDS height.
4 TDS provides strong evidence for the occurrence of a tornado. The tornadic vortex
5 pattern that can be provided by single polarization Doppler weather radars do not provide
6 evidence for the occurrence of a tornado, because a tornado (by definition) must
7 touchdown on the ground surface. By contrast, a TDS is result of tornado’s touchdown.
8 Moreover, an upstream TDS can provide valuable information that will allow downstream
9 or leeward areas to avoid danger (e.g., long-life tornadoes and/or large debris falls).
10 Although not all tornadoes have a TDS (Van Den Broeke and Jauernic 2014), TDS
11 detection is important for estimating the EF scale and damage area, providing evidence
12 for the occurrence of a tornado, and issuing tornado warnings.
13 The effects of land cover on TDSs have been studied in the United States (e.g., Van
14 Den Broeke and Jauernic 2014; Van Den Broeke 2015). As clarified from the context in
15 which the Japanese EF (JEF) scale was developed, the characteristics of the land cover
16 and artificial structures in Japan and the United States are different. However, only one
17 TDS event has been reported over a Japanese land cover (Yamauchi et al. 2013).
18 Yamauchi et al. (2013) reported the time–height distribution of TDSs produced by a
19 Fujita-scale-3 (F-3) tornado in Tsukuba City, Ibaraki, Japan. They also reported that the
20 parent storm of the Tsukuba tornado was a classic supercell and that the TDS was not
21 embedded in rain. For practical application, more information on the characteristics of
22 TDSs within various environments must be accumulated. However, there are no detailed
23 studies of TDSs within tropical cyclones.
24 The tornado associated with Typhoon Hagibis caused severe (JEF-2 scale) damage in
34 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 Ichihara City, Chiba, Japan. The event was observed using two operational C-band dual- 2 polarimetric weather radars and an X-band phased-array weather radar (PAWR). 3 The purpose of the present study is to clarify the characteristics of the TDSs of the 4 Ichihara tornado using two dual-polarization weather radars and determine the 5 relationship between the damage and the TDS distribution by comparing the TDSs with 6 both the tornadic vortexes detected by the PAWR and the land cover. 7 8 2. Damage situation 9 The Ichihara tornado was produced by a miniature supercell (Suzuki et al. 2000) 10 generated on the outer rain band of Typhoon Hagibis (2019) (Adachi and Mashiko 2020; 11 Morotomi et al. 2020). According to a field-survey report (Choshi Local Meteorological 12 Office 2021), damage incurred by the Ichihara tornado in Ichihara City, Chiba Prefecture, 13 began around 08:08 JST on October 12, 2019. The estimated length and width of the 14 damaged area were 1.6 km and 520 m, respectively. The tornado was rated JEF-2 (3-s 15 gusts of 53–66 m·s−1) on the JEF scale. The tornado completely destroyed 12 houses, 16 partially destroyed 23 houses, and partially damaged 54 houses. Much damage and 17 scatterings of tiled and tin roofs were reported. The tornado was observed using two 18 Doppler radars for airport weather (DRAWs) operated by the Japan Meteorological 19 Agency and a PAWR owned by Japan Radio Co., Ltd. The damage start point was 39.3 20 km from Tokyo International Airport (Haneda-DRAW), 33.8 km from Narita 21 International Airport (Narita-DRAW), and
SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 5
1 3. Methodology for the TDS study
2 3.1 TDS detection
3 Under the TDS criteria of Ryzkov et al. (2005) (Table 1), many TDSs were missed
4 because they fell below the ZHH threshold (Snyder and Ryzhkov 2015). Snyder and
5 Ryzhkov (2015) found that setting the upper bound of ρHV at ≤0.8 resulted in missed TDS
6 detections and many misclassifications as rain or hail (RH) or as unknown (UK) along
7 the TDS periphery, where rain may have mixed with the debris. These tendencies may be
8 important to tornadoes embedded in typhoon rain. To alleviate these problems, we tried
9 relaxing the detection conditions when confirming the temporal and spatial continuities.
10 The data range for TDSs overlaps with the following: RH, the melting layer, ground
11 clutter, and nonuniform beam filling (NBF, Ryzhkov 2007) (Snyder and Ryzhkov 2015).
12 The melting layer, ground clutter, and NBF can be excluded via quality control (e.g.,
13 filtering on the basis of the textures of differential phases between the copolar received
14 signals (ΨDP) and Vr). The remaining is RH. Schultz et al. (2012) noted that for C-band
15 radar, the typical ZDR values of RH are 2–3 dB or higher, while those of rain are ≥1 dB.
16 Thus, ZDR is useful for discriminating between TDS and RH. However, some previous
17 studies (e.g., Schultz et al. 2012) omitted the ZDR because of the difficulty of maintaining
18 its quality (Table 1). In those cases, because it is difficult to distinguish TDS from RH,
19 those studies tightened the ρHV condition (e.g., Schultz et al., 2012). Conversely, if the
20 ZDR can filter out RH, the ρHV threshold can be relaxed.
21 In this study, we therefore detected TDSs using the following conditions: ZHH > 40
22 dBZ, ρHV < 0.9, ZDR < 1.0 dB, MAD (Vr) > 5 m·s−1, MAD (ΨDP) < 20°, co-location with
23 hook echo, and a rotational Vr field (Table 1). Here, MAD denotes the median absolute
24 deviation. The MADs were used as texture data. The corrected ZHH and ZDR were used
56 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan
1 (details are in Supplement 1).
2
3 3.2 Parameters of TDS and tornadic vortex
4 As the TDS parameters, Bodine et al. (2013) and Wakimoto et al. (2020) adopted the
5 10th percentile of ZDR (q0.1{ZDR}), the 10th percentile of ρHV (q0.1{ρHV}), and the 90th
6 percentile of ZHH (q0.9{ZHH}) those variables that meet the TDS thresholds. To describe
7 the relationship between a TDS and an EF-scale rating, Bodine et al. (2013) also used the
8 maximum vertical extent and maximum volume. Van Den Broeke and Jauernic (2014)
9 demonstrated a clear relationship between the EF-scale rating and the aerial extent of
10 TDSs. In this study, we specified the following TDS parameters for detailed
11 characterizations of TDSs: minimum ZDR and q0.1{ZDR}, minimum ρHV, q0.1{ρHV},
12 maximum ZHH, q0.9{ZHH}, maximum vertical extent, TDS volume, and aerial extent
13 (defined as the area of the convex hull of the TDS bins). As the TDS volume, we used the
14 total sampling volumes of the TDS bins because the plan-position-indicator (PPI) scan
15 was not always volumetric. To obtain the representative values of the TDS, we also used
16 the median values of ZDR, ρHV, and ZHH.
17 As the tornadic vortex parameters, we used the radius and rotational velocity (Vrot) of
18 the pseudo-vortex calculated from the lowest and highest velocity peaks of the Doppler
19 velocity fields (Adachi et al. 2016; Adachi and Mashiko 2020). In this study, the tornadic
20 vortex parameters were derived only from PAWR data. Hereafter, “vortex” denotes the
21 counterclockwise vortex of a counter-rotating vortex pair, as described by Adachi and
22 Mashiko (2020). This includes both tornadoes and tornado cyclones (Burgess et al. 2002).
23SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 7
1 4. Results and discussion
2 4.1 Spatiotemporal distribution of the TDSs
3 In addition to a clear hook echo and a vortex pattern, we observed a region with low
4 ρHV and low or near-zero ZDR satisfying the TDS extraction conditions (Fig. 1). A TDS
5 satisfying the criteria of Ryzkov et al. (2005, colored purple in Fig. 1) was detected only
6 from 0808:51 to 0812:01 JST. However, the spatiotemporal continuities of ZHH, ZDR, and
7 ρHV indicate that the TDS-consistent region persisted. Under the conditions of the present
8 study, the limits on ZHH, ZDR, and ρHV were relaxed (Table 1) so that the TDS-detection
9 criteria identified the TDS-consistent region (the orange points in Fig. 1).
10 The TDS detection began ~1 min before (at Narita-DRAW) or immediately when (at
11 Haneda-DRAW) the vortex reached the damage-reported area, and the TDSs spread
12 horizontally and vertically over time (Fig. 2). In the latter half of the period (0805:00
13 JST + 300 s), they spread south–southwest with respect to the center of the vortex. The
14 total TDS distributions from Narita and Haneda-DRAW are consistent (Fig. 2), which
15 indicates that the quality of the input data is reliable. Note that the altitudes of the TDSs
16 depended on the scan sequence. The maximum vertical and aerial extents reached 2.4
17 km and 9.41 km2, respectively. (See the Supplement 2 for more detail).
18 Adachi et al. (2021) investigated the genesis of the Ichihara tornado and reported an
19 onset time of 0805:59 JST. Assuming that the first TDS (at 550 m ASL, 0807:01 JST)
20 was derived from the tornado onset (at 50 m, 0805:59 JST), we estimated the TDS rise
21 velocity to be 8 m·s−1, consistent with the rise velocity estimated by Bodine et al.
22 (2013). The time lag between the surface and the lowest PPI was estimated to be 1 min.
23
24 4.2 Temporal behavior of the TDS parameters
78 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan
1 Strong signatures (low q0.1{ρHV} and q0.1{ZDR} and high q0.9{ZHH}) appeared from
2 0808:51 to 0811:02 JST, ~1 min behind the period of strengthening of the surface vortex
3 [Fig. 3(a)(b)(c)(e)]. The ρHV minima and q0.1{ρHV} were smallest from 0810:02 to
4 0811:02 JST. After 0811:02 JST, they approached unity, and the TDS volume no longer
5 increased at Narita-DRAW [Fig. 3(c)].
6 At Narita, both the ZDR minima and the q0.1{ZDR} were minimized at 0811:02 JST
7 [Fig. 3 (b)]. The negative ZDR can be explained by the resonance effects (Ryzhkov et al.
8 2005; Bodine et al. 2014) or common vertical alignment of plate-like debris (Umeyama
9 et al. 2018). In the present case, alignment may have not occurred because the median
10 ZDR was almost stable at 0 dB [Fig. 3(b)], and the ZDR values varied from negative to
11 positive (see Section 4.4). Therefore, we considered resonance effects to be a more
12 reasonable explanation for the negative ZDR.
13 Except at 0811:02 and 0812:02 JST, the TDS volumes and the areas of the convex
14 hull were consistent between Narita and Haneda [Fig. 3(d)]. The TDS volume detected
15 by Narita-DRAW increased toward 0811:02 JST and began decreasing after 0812:02
16 JST. The convex-hull area continued to increase even after the TDS volume peaked.
17 This is probably because the spatial density of the TDS points was reduced by diffusion.
18 The decrease in the median ZHH and increase in the median ρHV [Fig. 3(b)(c)] support
19 debris diffusion. Note that the differences between the Narita- and Haneda-DRAWs
20 were assumed to result from differences in the debris distribution within the sampling
21 volume caused by time changes (~6 s) or from differences in the beam height and/or
22 resolution.
23
24 4.3 Correspondence of the TDS to the land coverSOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 9
1 At the touchdown time (0805:59 JST, estimated by Adachi et al. 2021), the lowest
2 vortex was passing over an area of deciduous or coniferous vegetation (Fig. 4).
3 Considering the time lag between surface touchdown and the occurrence of the lowest
4 TDS (~1 min), the first TDS detected at 0807:02 was likely to be composed mainly of
5 plant-derived debris (Fig. 4).
6 After reaching the residential area, the TDSs were well clarified (through either vortex
7 strengthening or the effects of the land cover). The minimum ρHV (0.27) and lower ρHV
8 among the TDS series were observed ~1 min after the tornado passed the most severely
9 damaged area (Fig. 4), and gradually increased over the next 4 min (Fig. 3(c) and Fig. 4),
10 suggesting that the heavy and/or dense debris was lofted and immediately fell out and/or
11 diffused, whereas the light debris remained airborne for at least 4 min. This ρHV
12 distribution is consistent with the findings of Wakimoto et al. (2020), who reported that
13 low ρHV occurred near the surface where debris loading was the greatest.
14 When the lowest vortex was most strengthened, the vortex was passing over cropland
15 outside the damage-reported region (the magenta two-way arrow in the middle panel of
16 Fig. 4). However, the absence of a damage report does not always imply the absence of
17 tornadic damage. According to Fig. 3(d), the TDS volume at 550 ASL (m) ceased to
18 increase at 0811:02 JST. Considering the time lag required to loft the debris, these
19 results are non-contradictory, even if the debris supply (i.e., the ground contact) were to
20 have continued until around 0810:00 JST. When the tornado again reached a residential
21 area after passing through cropland, the lowest vortex was > 60 m above ground level
22 and no damage report was filed. Therefore, tornado dissipation during 0809:29 and
23 0809:59 JST is reasonable estimation.
24
910 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan
1 4.4 Characteristics of the polarimetric variables in data space
2 At the lowest ρHV in each scan, ZDR was close to zero [Fig. 5(a)], but the value of ZHH
3 did not necessarily increase with decreasing ZDR [Fig. 5(b)] or with decreasing ρHV [Fig.
4 5(c)]. That is, the clarity of the TDS (such as low ρHV observed closer to the damaged
5 area) was not necessarily proportional to ZHH. Moreover, the results suggest the
6 limitations of using ZHH alone to discuss debris behavior.
7 Data dispersion was marked during the period 0808:35–0811:02 JST. After 0812:01
8 JST, the TDS points were concentrated above ρHV = 0.8. This concentration can be
9 explained by the increased fraction of rain content within the sampling volume as the
10 debris diffused (Schwarz and Burgess 2011; Bodine et al. 2013; Van Den Broeke and
11 Jauernic, 2014). We thus consider data dispersion as another useful indicator of TDS
12 behavior.
13 The q0.1{ρHV} and the q0.1{ZDR} were 0.69 and −0.87 dB, respectively, and the
14 q0.9{ZHH} was 50.29 dBZ. Similar parameters were derived for the EF-2-scale Stillwater
15 tornado and the EF-3-scale Lookeba tornado reported by Bodine et al. (2013).
16 Therefore, the relationships between the EF scale and the TDS parameters found by
17 Bodine et al. (2013) may also apply to the Japanese tornadoes with typhoon
18 backgrounds.
19
20 5. Summary
21 We analyzed the TDSs of the Ichihara tornado associated with Typhoon Hagibis
22 (2019). The data were observed using two operational C-band dual-polarimetric weather
23 radars and an X-band PAWR. This study was the first to conduct a detailed analysis ofSOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 11
1 the TDSs observed in a tropical cyclone. Moreover, we are the first to present
2 observations using two operational dual-polarimetric weather radars over Japanese land
3 cover.
4 The TDS bins spread horizontally and vertically over time, and the maximum vertical
5 extent was 2.4 km. The rise velocity was estimated as 8 m·s−1. The maximum aerial
6 extent reached 9.41 km2 at an elevation angle of 1.0° (the second-lowest elevation
7 angle).
8 The first TDS was detected ~1 min before the reported occurrence time of the tornado.
9 The TDSs became clearer (the q0.1{ρHV} and the q0.1{ZDR} decreased and the q0.1{ZHH}
10 increased) along with the Vrot of the near-surface vortex. The minimum ρHV (0.27) was
11 observed ~1 min after the tornado passed the most severely damaged area, and it gradually
12 increased over the next 4 min, suggesting that the heavy and/or debris was lofted and
13 immediately fell out and/or diffused, whereas the light debris remained airborne for at
14 least 4 min.
15 Comparing the TDSs with both the vortex parameters obtained using the PAWR and
16 aerial photographs, it was inferred that the first TDS comprised vegetated debris, the
17 clearest TDS mainly comprised destroyed manmade structures, and the TDS production
18 continued for 30–60 s (until 0809:29 or 0809:59 JST) after the tornado passed damage-
19 reported area.
20 Based on the characteristics of the polarimetric variables in data space, we show the
21 limitation of using ZHH alone to discuss debris behavior. We suggest data dispersion as
22 another useful indicator of TDS behavior. Finally, the relationships between the EF
23 scale and the TDS parameters obtained by Bodine et al. (2013) may be adoptable in the
24 Japanese tornado-with-typhoon scenario.
1112 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 These results, derived from operational radar data within the practical range, 2 demonstrate the efficacy of TDS detection for practical damage investigations and for 3 recognizing tornado’s occurrence. 4 5 Acknowledgments 6 The PAWR data were provided by Japan Radio Co., Ltd. The DRAW data were 7 provided by Atmosphere and Ocean Department, Japan Meteorological Agency. This 8 work was supported by the Japan Society for the Promotion of Science KAKENHI 9 Grant Numbers JP17K13007, JP19K23466, and JP20K04071. 10 11 Supplements 12 Supplement 1: Radar observations for Ichihara tornado. 13 Supplement 2: The detailed explanation of spatial distributions of TDSs. 14 15 References 16 Adachi, T., K. Kusunoki, S. Yoshida, H. Inoue, K. I. Arai, and T. Ushio, 2016: Rapid 17 volumetric growth of misocyclone and vault-like structure in horizontal shear 18 observed by phased array weather radar. Sci. Online Lett. Atmos., 12, 314–319, 19 https://doi.org/10.2151/SOLA.2016-061. 20 Adachi, T., and W. Mashiko, 2020: High Temporal-Spatial Resolution Observation of 21 Tornadogenesis in a Shallow Supercell Associated with Typhoon Hagibis (2019)
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15 List of Figure Captions
16 Fig. 1. Images of the TDS parameters observed using Narita-DRAW at 0.7° elevation.
17 The time (JST) is given at the top of each column: (Top) Vr (m·s−1), (upper middle)
18 ZHH (dBZ), (middle) ZDR, (lower middle) ρHV, and (bottom) TDS. The purple and
19 orange points in (at the bottom) indicate the TDS points satisfying the criteria of
20 Ryzkov et al. (2005) and this study, respectively. Each domain shows the same (10
21 × 10 km2) region, with the damaged area denoted by solid black-edged polygons.
22 The National Land Numerical Information (administrative region data) published by
23 the Ministry of Land, Infrastructure, Transport and Tourism are used for
1516 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 administrative boundaries. 2 Fig. 2. The spatial distribution of the TDSs detected using Narita-DRAW and Haneda- 3 DRAW. (a) TDS distribution (the scale bar indicates the number of seconds from 4 0805:00JST) observed using Narita-DRAW. (b) Longitude–height cross section of 5 (a). (c) and (d) Same as in (a) and (b) but observed using Haneda-DRAW. The 6 damaged area is indicated by the solid black-edged polygon. The solid gray-edged 7 circles in (a) and (b) indicate the diameters of the vortex at a height of 500 m detected 8 using the PAWR. The dotted circular arcs in (a) and (b) indicate the iso-distance 9 radius from each radar (35 km for Narita and Haneda-DRAW, 5 km for the PAWR). 10 The National Land Numerical Information (administrative region data) published by 11 the Ministry of Land, Infrastructure, Transport and Tourism are used for 12 administrative boundaries. 13 Fig. 3. Time series of the TDS parameters at 0.7° elevation observed using Narita-DRAW 14 (blue) and Haneda-DRAW (magenta). Shown are (a) ZHH (dBZ), (b) ZDR (dB), (c) 15 ρHV, (d) area (km2) (dashed lines) and volume (km3) (solid lines), and (e) the 16 rotational velocity (Vrot (m·s−1)) (black solid line) and the altitude of the lowest 17 vortex above ground level (10 km) (black dotted line) obtained using the PAWR. 18 The solid lines in (a) [(b) and (c)] show the maximum (minimum) for each variable. 19 The dashed lines in (a) [(b) and (c)] show the 90th (10th) percentile for each variable. 20 The dotted lines in (a), (b) and (c) show the median for each variable. The lowest 21 PPI (0.7° elevation) was chosen for two reasons: first, the scan was most frequently 22 and the interval was constant (1 min); second, it was expected that the lowest PPI 23 was related to the surface-vortex activity. 24 Fig. 4. (Top) Longitude–height section of the vortex rotational velocities and diameters
SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 17
1 derived using the PAWR. The black solid line indicates the altitude of the lowest
2 vortex above ground level (0.5 km). The gray-filled region represents the terrain.
3 The magenta two-way arrow represents the damage-reported region. (Middle) Land-
4 cover type estimated from an aerial photograph. (Bottom) Aerial photograph with
5 TDSs colored by the ρHV values and the vortex detected by the PAWR. The numbers
6 on the bubble chart and at the centers of the surface-vortex locations correspond to
7 the detection time (in minutes and seconds of JST). The TDSs detected by the Narita
8 (Haneda)-DRAW are indicated by diamonds (squares). The damaged area is
9 indicated by the black-edged closed polygon. The top, middle, and bottom panels
10 share the same horizontal axis (longitude). The “GSI tile” published by Geospatial
11 Information Authority of Japan is used for aerial photograph.
12 Fig. 5. Scatter plots of the TDS parameters observed using the Narita- and Haneda-
13 DRAWs showing (a) ZDR versus ρHV, (b) ZDR versus ZHH, and (c) ZHH versus ρHV.
14 The plot colors indicate the scan times, which are shown in the scale to the right of
15 panel (c). The solid lines delineate the convex hulls of the scattered data at each scan
16 time. The black dotted lines indicate the 10th percentiles (the 90th percentile) of ρHV
17 and ZDR (ZHH), and the gray dotted lines show their 95% confidence intervals based
18 on 1000 bootstrap resamples.
19
20 List of Table Captions
21 Table 1. Comparison of criteria used to identify TDS bins in this and previous studies.
22 The quantities AS, MAD, and STD denote the azimuthal shear, median absolute
23 deviation, and standard deviation, respectively.
1718 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 Table 1: Comparison of criteria used to identify TDS bins in this and previous studies. 2 The quantities AS, MAD, and STD denote the azimuthal shear, median absolute 3 deviation, and standard deviation, respectively. 4 5 6 7 8 9 10 11 12 13
SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 19
1
2 Fig. 1. Images of the TDS parameters observed using Narita-DRAW at 0.7° elevation.
3 The time (JST) is given at the top of each column: (Top) Vr (m·s−1), (upper middle)
4 ZHH (dBZ), (middle) ZDR, (lower middle) ρHV, and (bottom) TDS. The purple and
5 orange points in (at the bottom) indicate the TDS points satisfying the criteria of
6 Ryzkov et al. (2005) and this study, respectively. Each domain shows the same (10
7 × 10 km2) region, with the damaged area denoted by solid black-edged polygons.
8 The National Land Numerical Information (administrative region data) published by
9 the Ministry of Land, Infrastructure, Transport and Tourism are used for
10 administrative boundaries.
11
12
1920 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 2 Fig. 2. The spatial distribution of the TDSs detected using Narita-DRAW and Haneda- 3 DRAW. (a) TDS distribution (the scale bar indicates the number of seconds from 4 0805:00JST) observed using Narita-DRAW. (b) Longitude–height cross section of 5 (a). (c) and (d) Same as in (a) and (b) but observed using Haneda-DRAW. The 6 damaged area is indicated by the solid black-edged polygon. The solid gray-edged 7 circles in (a) and (b) indicate the diameters of the vortex at a height of 500 m detected 8 using the PAWR. The dotted circular arcs in (a) and (b) indicate the iso-distance 9 radius from each radar (35 km for Narita and Haneda-DRAW, 5 km for the PAWR). 10 The National Land Numerical Information (administrative region data) published by 11 the Ministry of Land, Infrastructure, Transport and Tourism are used for 12 administrative boundaries. 13
SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 21
1
2 Fig. 3. Time series of the TDS parameters at 0.7° elevation observed using Narita-DRAW
3 (blue) and Haneda-DRAW (magenta). Shown are (a) ZHH (dBZ), (b) ZDR (dB), (c)
4 ρHV, (d) area (km2) (dashed lines) and volume (km3) (solid lines), and (e) the
5 rotational velocity (Vrot (m·s−1)) (black solid line) and the altitude of the lowest
6 vortex above ground level (10 km) (black dotted line) obtained using the PAWR.
7 The solid lines in (a) [(b) and (c)] show the maximum (minimum) for each variable.
8 The dashed lines in (a) [(b) and (c)] show the 90th (10th) percentile for each variable.
9 The dotted lines in (a), (b) and (c) show the median for each variable. The lowest
10 PPI (0.7° elevation) was chosen for two reasons: first, the scan was most frequently
11 and the interval was constant (1 min); second, it was expected that the lowest PPI
12 was related to the surface-vortex activity.
2122 Umehara et al., Analysis of Tornadic Debris Signatures of Ichihara Tornado, Japan 1 2 Fig. 4. (Top) Longitude–height section of the vortex rotational velocities and diameters 3 derived using the PAWR. The black solid line indicates the altitude of the lowest 4 vortex above ground level (0.5 km). The gray-filled region represents the terrain. 5 The magenta two-way arrow represents the damage-reported region. (Middle) Land- 6 cover type estimated from an aerial photograph. (Bottom) Aerial photograph with 7 TDSs colored by the ρHV values and the vortex detected by the PAWR. The numbers 8 on the bubble chart and at the centers of the surface-vortex locations correspond to 9 the detection time (in minutes and seconds of JST). The TDSs detected by the Narita 10 (Haneda)-DRAW are indicated by diamonds (squares). The damaged area is 11 indicated by the black-edged closed polygon. The top, middle, and bottom panels 12 share the same horizontal axis (longitude). The “GSI tile” published by Geospatial 13 Information Authority of Japan is used for aerial photograph.
SOLA, 2021, Vol. 17, 196-199(TBA), doi:10.2151/sola.2021-034 23
1
2 Fig. 5. Scatter plots of the TDS parameters observed using the Narita- and Haneda-
3 DRAWs showing (a) ZDR versus ρHV, (b) ZDR versus ZHH, and (c) ZHH versus ρHV.
4 The plot colors indicate the scan times, which are shown in the scale to the right of
5 panel (c). The solid lines delineate the convex hulls of the scattered data at each scan
6 time. The black dotted lines indicate the 10th percentiles (the 90th percentile) of ρHV
7 and ZDR (ZHH), and the gray dotted lines show their 95% confidence intervals based
8 on 1000 bootstrap resamples.
9
10
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