scholarly journals Evolution of Cloud-to-Ground Lightning and Storm Structure in the Spencer, South Dakota, Tornadic Supercell of 30 May 1998

2003 ◽  
Vol 131 (8) ◽  
pp. 1811-1831 ◽  
Author(s):  
Lawrence D. Carey ◽  
Walter A. Petersen ◽  
Steven A. Rutledge
Keyword(s):  
South Dakota ◽  
Lightning Activity ◽  
Squall Line ◽  
Doppler Velocity ◽  
Lightning Flash ◽  
Flash Rate ◽  
Storm Evolution ◽  
Supercell Storms ◽  
The Difference ◽  
Cg Lightning

Abstract On 30 May 1998, a tornado devastated the town of Spencer, South Dakota. The Spencer tornado (rated F4 on the Fujita tornado intensity scale) was the third and most intense of five tornadoes produced by a single supercell storm during an approximate 1-h period. The supercell produced over 76% positive cloud-to-ground (CG) lightning and a peak positive CG flash rate of 18 flashes min−1 (5-min average) during a 2-h period surrounding the tornado damage. Earlier studies have reported anomalous positive CG lightning activity in some supercell storms producing violent tornadoes. However, what makes the CG lightning activity in this tornadic storm unique is the magnitude and timing of the positive ground flashes relative to the F4 tornado. In previous studies, supercells dominated by positive CG lightning produced their most violent tornado after they attained their maximum positive ground flash rate, whenever the rate exceeded 1.5 flashes min−1. Further, tornadogenesis often occurred during a lull in CG lightning activity and sometimes during a reversal from positive to negative polarity. Contrary to these findings, the positive CG lightning flash rate and percentage of positive CG lightning in the Spencer supercell increased dramatically while the storm was producing F4 damage on Spencer. These results have important implications for the use of CG lightning in the nowcasting of tornadoes and for the understanding of cloud electrification in these unique storms. In order to further explore these issues, the authors present detailed analyses of storm evolution and structure using Sioux Falls, South Dakota, (KFSD) Weather Surveillance Radar-1988 Doppler (WSR-88D) radar reflectivity and Doppler velocity and National Lightning Detection Network (NLDN) CG lightning data. The analyses suggest that a merger between the Spencer supercell and a squall line on its rear flank may have provided the impetus for both the F4 tornadic damage and the dramatic increase in positive CG lightning during the tornado, possibly explaining the difference in timing compared to past studies.

scholarly journals Revisiting Lightning Activity and Parameterization Using Geostationary Satellite Observations

2021 ◽  
Vol 13 (19) ◽  
pp. 3866
Author(s):  
Xin Zhang ◽  
Yan Yin ◽  
Julia Kukulies ◽  
Yang Li ◽  
Xiang Kuang ◽  
...  
Keyword(s):  
Robust Statistics ◽  
Detection Efficiency ◽  
Lightning Activity ◽  
Power Relationship ◽  
Lightning Flash ◽  
Flash Rate ◽  
The Difference ◽  
Total Lightning ◽  
The Tropics ◽  
The Relationship

The Geostationary Lightning Mapper (GLM) on the Geostationary Operational Environmental Satellite 16 (GOES-16) detects total lightning continuously, with a high spatial resolution and detection efficiency. Coincident data from the GLM and the Advanced Baseline Imager (ABI) are used to explore the correlation between the cloud top properties and flash activity across the continental United States (CONUS) sector from May to September 2020. A large number of collocated infrared (IR) brightness temperature (TBB), cloud top height (CTH) and lightning data provides robust statistics. Overall, the likelihood of lightning occurrence and high flash density is higher if the TBB is colder than 225 K. The higher CTH is observed to be correlated with a larger flash rate, a smaller flash size, stronger updraft, and larger optical energy. Furthermore, the cloud top updraft velocity (w) is estimated based on the decreasing rate of TBB, but it is smaller than the updraft velocity of the convective core. As a result, the relationship between CTH and lightning flash rate is investigated independently of w over the continental, oceanic and coastal regimes in the tropics and mid-latitudes. When the CTH is higher than 12 km, the flash rates of oceanic lightning are 38% smaller than those of both coastal and continental lightning. In addition, it should be noted that more studies are necessary to examine why the oceanic lightning with low clouds (CTH < 8 km) has higher flash rates than lightning over land and coast. Finally, the exponents of derived power relationship between CTH and lightning flash rate are smaller than four, which is underestimated due to the GLM detection efficiency and the difference between IR CTH and 20 dBZ CTH. The results from combining the ABI and GLM products suggest that merging multiple satellite datasets could benefit both lightning activity and parameterization studies, although the parallax corrections should be considered.

Thermodynamic Contribution to Lightning Activity in the Fourth Chimney

2021 ◽  
Author(s):  
Earle Williams ◽  
Diego Enore ◽  
Enrique Mattos ◽  
Yen-Jung Joanne Wu
Keyword(s):  
Convective Available Potential Energy ◽  
Lightning Activity ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Lightning Flash ◽  
Schumann Resonance ◽  
Flash Rate ◽  
Zonal Wavenumber ◽  
Usual Behavior ◽  
Total Lightning

&lt;p&gt;Lightning activity over oceans is normally greatly suppressed in comparison with continents.&amp;#160; The most conspicuous region of enhanced lightning activity over open ocean is found in the equatorial Pacific (150 W) in many global lightning climatologies (OTD, LIS, WWLLN, GLD360, RHESSI, Schumann resonance Q-bursts) and is associated with the South Pacific Convergence Zone (SPCZ).&amp;#160; This oceanic lightning anomaly completes the zonal wavenumber-4 structure of continent-based lightning maxima (with nominal 90-degree longitudinal separation between sources), and so is appropriately named &amp;#8220;the fourth chimney&amp;#8221;.&amp;#160; This region is now under continuous surveillance by the Geostationary Lightning Mapper (GLM) on the GOES-17 satellite (at 137 W).&amp;#160; This total lightning activity is compared with Convective Available Potential Energy (CAPE) from ERA-5 reanalysis.&amp;#160; These CAPE values are correlated with values extracted from thermodynamic soundings at proximal stations Atuona, Rikitea and Tahiti. &amp;#160;The shape of the regional climatology of CAPE resembles that of the SPCZ and is oblique to the equator.&amp;#160; The total lightning flash rate is positively correlated with CAPE, and lightning locations are found preferentially in regions of elevated CAPE on individual days.&amp;#160; The diurnal variation of total lightning for January exceeds a factor-of-two and shows a phase at odds with the usual behavior of oceanic lightning near continents.&lt;/p&gt;

scholarly journals The 30 May 1998 Spencer, South Dakota, Storm. Part I: The Structural Evolution and Environment of the Tornadoes

2005 ◽  
Vol 133 (1) ◽  
pp. 72-97 ◽  
Author(s):  
Curtis R. Alexander ◽  
Joshua Wurman
Keyword(s):  
South Dakota ◽  
Detailed Comparison ◽  
Squall Line ◽  
Doppler Velocity ◽  
Time Interval ◽  
Moist Convection ◽  
Atmospheric Conditions ◽  
Surface Shear ◽  
Near Surface ◽  
Vertical Vorticity

Abstract On the evening of 30 May 1998 atmospheric conditions across southeastern South Dakota led to the development of organized moist convection including several supercells. One such supercell was tracked by both a Weather Surveillance Radar-1988 Doppler (WSR-88D) from Sioux Falls, South Dakota (KFSD), and by a Doppler On Wheels (DOW) mobile radar. This supercell remained isolated for an hour and a half before being overtaken by a developing squall line. During this time period the supercell produced at least one strong and one violent tornado, the latter of which passed through Spencer, South Dakota, despite the absence of strong low-level environmental wind shear. The two tornadoes were observed both visually and with the DOW radar at ranges between 1.7 and 12.9 km. The close proximity to the tornadoes permitted the DOW radar to observe tornado-scale structures on the order of 35 to 100 m, while the nearest WSR-88D only resolved the parent mesocyclone in the supercell. The DOW observations revealed a persistent Doppler velocity couplet and associated ring reflectivity signature at the tip of the hook echo. The DOW radar data contained tornado strength winds over 35 m s−1 within 100 m AGL approximately 180 s prior to both the first spotter report and visual confirmation of the first tornado associated with this supercell. Following the formation of the second tornado, the DOW radar observations revealed a tornado-strength Doppler velocity couplet within 150 m AGL between two separate tornado tracks determined by a National Weather Service (NWS) damage survey. Based upon the DOW Doppler velocity data it appears that the second and third damage tracks from this supercell are produced from a single tornado. The time–height evolution of the Doppler velocity couplet spanning both tornadoes revealed a gradual increase in vertical vorticity across each tornado's core region within a few hundred meters AGL from near 0.2 to over 2.0 s−1 over a 45-min period. A corresponding reduction in vertical vorticity was observed aloft especially near 1000 m AGL where vorticity values decreased from near 1.0 to about 0.5 s−1 during this same time interval. The shear across the Doppler velocity couplet appears to undergo strengthening both at the surface and aloft during both tornadoes. An oscillatory fluctuation in the near-surface shear across the tornado core developed during the second tornado, with peak shear values as high as 206 m s−1, Doppler velocities over 106 m s−1, and peak ground-relative wind speeds reaching 118 m s−1. The period of this intensity oscillation appears to be around 120 s and was most prominent just prior to and during the passage of the tornado through Spencer. Coincident with the tornado passage through Spencer was a rapid descending of the reflectivity eye in the core of the tornado. A detailed comparison of surveyed tornado damage and radar-calculated tornado winds in Spencer is discussed in Part II.

scholarly journals Characteristics of cloud-to-ground lightning activity over Seoul, South Korea in relation to an urban effect

2007 ◽  
Vol 25 (10) ◽  
pp. 2113-2118 ◽  
Author(s):  
S. K. Kar ◽  
Y.-A. Liou ◽  
K.-J. Ha
Keyword(s):  
South Korea ◽  
Correlation Coefficients ◽  
Lightning Activity ◽  
Lightning Flash ◽  
Urban Effect ◽  
Percentage Decrease ◽  
Lightning Detection ◽  
Cloud To Ground Lightning ◽  
The City ◽  
Cg Lightning

Abstract. Cloud-to-ground (CG) lightning flash data collected by the lightning detection network installed at the Korean Meteorological Administration (KMA) have been used to study the urban effect on lightning activity over and around Seoul, the largest metropolitan city of South Korea, for the period of 1989–1999. Negative and positive flash density and the percentage of positive flashes have been calculated. Calculation reveals that an enhancement of approximately 60% and 42% are observed, respectively, for negative and positive flash density over and downwind of the city. The percentage decrease of positive flashes occurs over and downwind of Seoul and the amount of decrease is nearly 20% compared to upwind values. The results are in good agreement with those obtained by Steiger et al. (2002) and Westcott (1995). CG lightning activities have also been considered in relation to annual averages of PM10 (particulate matter with an aerodynamic diameter smaller than 10 μm) and sulphur dioxide (SO2) concentrations. Interesting results are found, indicating that the higher concentration of SO2 contributes to the enhancement of CG lightning flashes. On the other hand, the contribution from PM10 concentration has not appeared in this study to be as significant as SO2 in the enhancement of CG lightning flashes. Correlation coefficients of 0.33 and 0.64 are found between the change in CG lightning flashes and the PM10 and SO2, respectively, for upwind to downwind areas, suggesting a significant influence of the increased concentration of SO2 on the enhancement of CG flashes.

scholarly journals Microphysical retrievals from simultaneous polarimetric and profiling radar observations

2009 ◽  
Vol 27 (12) ◽  
pp. 4435-4448 ◽  
Author(s):  
M. P. Morris ◽  
P. B. Chilson ◽  
T. J. Schuur ◽  
A. Ryzhkov
Keyword(s):  
Remote Sensing Data ◽  
Weather Radar ◽  
Ground Truth ◽  
Ambient Air ◽  
Exponential Model ◽  
Squall Line ◽  
Doppler Velocity ◽  
Wind Profiler ◽  
Polarimetric Weather Radar ◽  
Velocity Spectra

Abstract. The character of precipitation detected at the surface is the final product of many microphysical interactions in the cloud above, the combined effects of which may be characterized by the observed drop size distribution (DSD). This necessitates accurate retrieval of the DSD from remote sensing data, especially radar as it offers large areal coverage, high spatial resolution, and rigorous quality control and testing. Combined instrument observations with a UHF wind profiler, an S-band polarimetric weather radar, and a video disdrometer are analyzed for two squall line events occuring during the calendar year 2007. UHF profiler Doppler velocity spectra are used to estimate the DSD aloft, and are complemented by DSDs retrieved from an exponential model applied to polarimetric data. Ground truth is provided by the disdrometer. A complicating factor in the retrieval from UHF profiler spectra is the presence of ambient air motion, which can be corrected using the method proposed by Teshiba et al. (2009), in which a comparison between idealized Doppler spectra calculated from the DSDs retrieved from KOUN and those retrieved from contaminated wind profiler spectra is performed. It is found that DSDs measured using the distrometer at the surface and estimated using the wind profiler and polarimetric weather radar generally showed good agreement. The DSD retrievals using the wind profiler were improved when the estimates of the vertical wind were included into the analysis, thus supporting the method of Teshiba et al. (2009). Furthermore, the the study presents a method of investigating the time and height structure of DSDs.

scholarly journals The spatio-temporal distribution of lightning over Israel and the neighboring area and its relation to regional synoptic systems

2011 ◽  
Vol 11 (8) ◽  
pp. 2125-2135 ◽  
Author(s):  
S. Shalev ◽  
H. Saaroni ◽  
T. Izsak ◽  
Y. Yair ◽  
B. Ziv
Keyword(s):  
Spatial Distribution ◽  
Mediterranean Sea ◽  
Temporal Distribution ◽  
Lightning Activity ◽  
Eastern Coast ◽  
Synoptic Situation ◽  
Lightning Flash ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
Neighboring Area

Abstract. The spatio-temporal distribution of lightning flashes over Israel and the neighboring area and its relation to the regional synoptic systems has been studied, based on data obtained from the Israel Lightning Location System (ILLS) operated by the Israel Electric Corporation (IEC). The system detects cloud-to-ground lightning discharges in a range of ~500 km around central Israel (32.5° N, 35° E). The study period was defined for annual activity from August through July, for 5 seasons in the period 2004–2010. The spatial distribution of lightning flash density indicates the highest concentration over the Mediterranean Sea, attributed to the contribution of moisture as well as sensible and latent heat fluxes from the sea surface. Other centers of high density appear along the coastal plain, orographic barriers, especially in northern Israel, and downwind from the metropolitan area of Tel Aviv, Israel. The intra-annual distribution shows an absence of lightning during the summer months (JJA) due to the persistent subsidence over the region. The vast majority of lightning activity occurs during 7 months, October to April. Although over 65 % of the rainfall in Israel is obtained during the winter months (DJF), only 35 % of lightning flashes occur in these months. October is the richest month, with 40 % of total annual flashes. This is attributed both to tropical intrusions, i.e., Red Sea Troughs (RST), which are characterized by intense static instability and convection, and to Cyprus Lows (CLs) arriving from the west. Based on daily study of the spatial distribution of lightning, three patterns have been defined; "land", "maritime" and "hybrid". CLs cause high flash density over the Mediterranean Sea, whereas some of the RST days are typified by flashes over land. The pattern defined "hybrid" is a combination of the other 2 patterns. On CL days, only the maritime pattern was noted, whereas in RST days all 3 patterns were found, including the maritime pattern. It is suggested that atmospheric processes associated with RST produce the land pattern. Hence, the occurrence of a maritime pattern in days identified as RST reflects an "apparent RST". The hybrid pattern was associated with an RST located east of Israel. This synoptic type produced the typical flash maximum over the land, but the upper-level trough together with the onshore winds it induced over the eastern coast of the Mediterranean resulted in lightning activity over the sea as well, similar to that of CLs. It is suggested that the spatial distribution patterns of lightning may better identify the synoptic system responsible, a CL, an "active RST" or an "apparent RST". The electrical activity thus serves as a "fingerprint" for the synoptic situation responsible for its generation.

scholarly journals Distinct aerosol effects on cloud-to-ground lightning in the plateau and basin regions of Sichuan, Southwest China

2020 ◽  
Vol 20 (21) ◽  
pp. 13379-13397
Author(s):  
Pengguo Zhao ◽  
Zhanqing Li ◽  
Hui Xiao ◽  
Fang Wu ◽  
Youtong Zheng ◽  
...  
Keyword(s):  
Cloud Droplet ◽  
Lightning Activity ◽  
Freezing Process ◽  
Plateau Region ◽  
Freezing Level ◽  
Aerosol Loading ◽  
Cloud To Ground Lightning ◽  
Basin Region ◽  
Total Column ◽  
Cg Lightning

Abstract. The joint effects of aerosol, thermodynamic, and cloud-related factors on cloud-to-ground lightning in Sichuan were investigated by a comprehensive analysis of ground-based measurements made from 2005 to 2017 in combination with reanalysis data. Data include aerosol optical depth, cloud-to-ground (CG) lightning density, convective available potential energy (CAPE), mid-level relative humidity, lower- to mid-tropospheric vertical wind shear, cloud-base height, total column liquid water (TCLW), and total column ice water (TCIW). Results show that CG lightning density and aerosols are positively correlated in the plateau region and negatively correlated in the basin region. Sulfate aerosols are found to be more strongly associated with lightning than total aerosols, so this study focuses on the role of sulfate aerosols in lightning activity. In the plateau region, the lower aerosol concentration stimulates lightning activity through microphysical effects. Increasing the aerosol loading decreases the cloud droplet size, reducing the cloud droplet collision–coalescence efficiency and inhibiting the warm-rain process. More small cloud droplets are transported above the freezing level to participate in the freezing process, forming more ice particles and releasing more latent heat during the freezing process. Thus, an increase in the aerosol loading increases CAPE, TCLW, and TCIW, stimulating CG lightning in the plateau region. In the basin region, by contrast, the higher concentration of aerosols inhibits lightning activity through the radiative effect. An increase in the aerosol loading reduces the amount of solar radiation reaching the ground, thereby lowering the CAPE. The intensity of convection decreases, resulting in less supercooled water being transported to the freezing level and fewer ice particles forming, thereby increasing the total liquid water content. Thus, an increase in the aerosol loading suppresses the intensity of convective activity and CG lightning in the basin region.

scholarly journals A Hail Growth Trajectory Model for Exploring the Environmental Controls on Hail Size: Model Physics and Idealized Tests

2020 ◽  
Vol 77 (8) ◽  
pp. 2765-2791 ◽  
Author(s):  
Matthew R. Kumjian ◽  
Kelly Lombardo
Keyword(s):  
Residence Time ◽  
Vertical Wind Shear ◽  
Squall Line ◽  
Model Parameters ◽  
Convective Storms ◽  
Environmental Controls ◽  
Supercell Storm ◽  
Uncertain Model ◽  
Supercell Storms ◽  
Microphysical Processes

Abstract A detailed microphysical model of hail growth is developed and applied to idealized numerical simulations of deep convective storms. Hailstone embryos of various sizes and densities may be initialized in and around the simulated convective storm updraft, and then are tracked as they are advected and grow through various microphysical processes. Application to an idealized squall line and supercell storm results in a plausibly realistic distribution of maximum hailstone sizes for each. Simulated hail growth trajectories through idealized supercell storms exhibit many consistencies with previous hail trajectory work that used observed storms. Systematic tests of uncertain model parameters and parameterizations are performed, with results highlighting the sensitivity of hail size distributions to these changes. A set of idealized simulations is performed for supercells in environments with varying vertical wind shear to extend and clarify our prior work. The trajectory calculations reveal that, with increased zonal deep-layer shear, broader updrafts lead to increased residence time and thus larger maximum hail sizes. For cases with increased meridional low-level shear, updraft width is also increased, but hailstone sizes are smaller. This is a result of decreased residence time in the updraft, owing to faster northward flow within the updraft that advects hailstones through the growth region more rapidly. The results suggest that environments leading to weakened horizontal flow within supercell updrafts may lead to larger maximum hailstone sizes.

Intraseasonal Forcing of Convection and Lightning Activity in the Southern Amazon as a Function of Cross-Equatorial Flow

2006 ◽  
Vol 19 (13) ◽  
pp. 3180-3196 ◽  
Author(s):  
Walter A. Petersen ◽  
Rong Fu ◽  
Mingxuan Chen ◽  
Richard Blakeslee
Keyword(s):  
Wind Shear ◽  
Lightning Activity ◽  
Lightning Flash ◽  
Easterly Wind ◽  
Water Path ◽  
Low Level ◽  
Ice Water Path ◽  
Stratiform Precipitation ◽  
Ice Water ◽  
Thermodynamic Instability

Abstract This study focuses on modulation of lightning and convective vertical structure in the southern Amazon as a function of the South American monsoon V index (VI). Four wet seasons (December–March 1998–2001) of Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) and Precipitation Radar (PR) data are examined together with two wet seasons (2000–01) of ground-based Brazilian Lightning Detection Network (BLDN) data. These observations are composited by VI phase (northerly or southerly) for a region of the southern Amazon and discussed relative to VI-regime environmental characteristics such as thermodynamic instability and wind shear. Relative comparisons of VI-regime convective properties reveal 1) slightly larger (20%–25%) PR pixel-mean rainfall during periods of northerly VI due to increased stratiform precipitation, 2) a factor of 2 or more increase in lightning flash density and the lightning diurnal cycle amplitude during periods of southerly VI, 3) a factor of 1.5–2 increase in the conditional probability of any PR radar reflectivity pixel exceeding 30 dBZ above the −10°C level during periods of southerly VI, and 4) an associated factor of 2 or more increase in southerly VI pixel-mean ice water path, with the ice water path being highly correlated to trends in lightning activity. During periods of southerly VI, convection occurs in an environment of increased thermodynamic instability, weak southeasterly low-level, and deep upper-tropospheric easterly wind shear. During periods of northerly VI, low-level westerly shear opposes stronger deep tropospheric easterly shear in a relatively moist environment of weaker thermodynamic instability, consistent with the occurrence of more widespread stratiform precipitation. The composite results of this study point to 1) regime differences in convective forcing that alter the prevalence of ice processes and, by inference, the vertical profile of latent heating and 2) the utility of lightning observations in delineating convective regime changes.

Assessment of a ground-based lightning detection and near real-time warning system in the rural community of Swayimane, KwaZulu-Natal, South Africa

2021 ◽  
Author(s):  
Maqsooda Mahomed ◽  
Alistair D. Clulow ◽  
Sheldon Strydom ◽  
Tafadzwanashe Mabhaudhi ◽  
Michael J. Savage
Keyword(s):  
South Africa ◽  
Rural Communities ◽  
Warning System ◽  
Lightning Activity ◽  
Lightning Flash ◽  
Short Message ◽  
Remote Server ◽  
Kwazulu Natal ◽  
Education And Awareness ◽  
Multiple Network

AbstractClimate change projections of increases in lightning activity are an added concern for lightning-prone countries such as South Africa. South Africa’s high levels of poverty, lack of education and awareness, as well as a poorly developed infrastructure increases the vulnerability of rural communities to the threat of lightning. Despite the existence of national lightning networks, lightning alerts and warnings are not disseminated well to such rural communities. We therefore developed a community-based early warning system (EWS) to detect and disseminate lightning threats and alerts in a timeous and comprehensible manner within Swayimane, KwaZulu-Natal, South Africa. The system comprised of an electrical field meter and a lightning flash sensor with warnings disseminated via audible and visible alarms on-site and with a remote server issuing short message services (SMSs) and email alerts. Twelve months of data (February 2018-February 2019) were utilized to evaluate the performance of the EWS’s detection and warning capabilities. Diurnal variations in lightning activity indicated the influence of solar radiation, causing convective conditions with peaks in lightning activity occurring during the late afternoon and early evening (between 14h00 and 21h00) coinciding with learners being released from school and when most workers return home. In addition to detecting the threat of lightning, the EWS was beneficial in identifying periods that exhibited above-normal lightning activity with two specific lightning events examined in detail. Poor network signals in rural communities was an initial challenge delaying data transmission to the central server until rectified using multiple network providers. Overall, the EWS was found to disseminate reliable warnings timeously.

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