scholarly journals Radar Nowcasting of Cloud-to-Ground Lightning over Houston, Texas

2011 ◽  
Vol 26 (2) ◽  
pp. 199-212 ◽  
Author(s):  
Richard M. Mosier ◽  
Courtney Schumacher ◽  
Richard E. Orville ◽  
Lawrence D. Carey
Keyword(s):  
Convective Cell ◽  
Lead Times ◽  
Lightning Flash ◽  
Critical Success ◽  
Lightning Detection ◽  
Doppler Data ◽  
Cloud To Ground Lightning ◽  
A Cell ◽  
Convective Cells ◽  
Critical Success Index

Abstract Ten years (1997–2006) of summer (June–August) daytime (1400–0000 UTC) Weather Surveillance Radar-1988 Doppler data for Houston, Texas, were examined to determine the best radar-derived predictors of the first cloud-to-ground lightning flash from a convective cell. Convective cells were tracked using a modified version of the Storm Cell Identification and Tracking (SCIT) algorithm and then correlated to cloud-to-ground lightning data from the National Lightning Detection Network (NLDN). Combinations of three radar reflectivity values (30, 35, and 40 dBZ) at four isothermal levels (−10°, −15°, −20°, and updraft −10°C) and a new radar-derived product, vertically integrated ice (VII), were used to optimize a radar-based lightning forecast algorithm. Forecasts were also delineated by range and the number of times a cell was identified and tracked by the modified SCIT algorithm. This study objectively analyzed 67 384 unique cells and 1 028 510 lightning flashes to find the best lightning forecast criteria. Results show that using 30 dBZ at the −15° or −20°C isotherm on cells within 75 km of the radar that have been tracked for at least two consecutive scans produces the best lightning forecasts with a critical success index (CSI) of 0.68. The best VII predictor values were 0.42 or 0.58 kg m−2 on cells within 75 km of the radar that have been tracked for at least two consecutive scans, producing a CSI of 0.67. Lead times for these predictors were 10.0 and 13.4 min, respectively. Lead times greater than 10 min occurred with less stringent predictors (e.g., 30 dBZ at −10°C or VII greater than 0.25 kg m−2 on cells within 125 km with a minimum track count of 2), but lower CSI values result. In general, cells tracked for multiple scans provide higher CSIs and lead times than decreasing the range from the radar or changing the reflectivity threshold and height.

scholarly journals A Total Lightning Trending Algorithm to Identify Severe Thunderstorms

2010 ◽  
Vol 27 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Patrick N. Gatlin ◽  
Steven J. Goodman
Keyword(s):  
Severe Weather ◽  
Lightning Flash ◽  
Severe Thunderstorm ◽  
Critical Success ◽  
Severe Thunderstorms ◽  
Weather Events ◽  
Total Lightning ◽  
Jump Algorithm ◽  
Early Indication ◽  
Critical Success Index

Abstract An algorithm that provides an early indication of impending severe weather from observed trends in thunderstorm total lightning flash rates has been developed. The algorithm framework has been tested on 20 thunderstorms, including 1 nonsevere storm, which occurred over the course of six separate days during the spring months of 2002 and 2003. The identified surges in lightning rate (or jumps) are compared against 110 documented severe weather events produced by these thunderstorms as they moved across portions of northern Alabama and southern Tennessee. Lightning jumps precede 90% of these severe weather events, with as much as a 27-min advance notification of impending severe weather on the ground. However, 37% of lightning jumps are not followed by severe weather reports. Various configurations of the algorithm are tested, and the highest critical success index attained is 0.49. Results suggest that this lightning jump algorithm may be a useful operational diagnostic tool for severe thunderstorm potential.

scholarly journals A 10-Year Study on the Characteristics of Thunderstorms in Belgium Based on Cloud-to-Ground Lightning Data

2014 ◽  
Vol 142 (12) ◽  
pp. 4839-4849 ◽  
Author(s):  
Dieter R. Poelman
Keyword(s):  
Cell Tracking ◽  
Total Activity ◽  
The West ◽  
European Cooperation ◽  
Lightning Detection ◽  
Cloud To Ground Lightning ◽  
A Cell ◽  
Direction Of Movement ◽  
Temporal And Spatial ◽  
The Individual

Abstract Temporal and spatial distributions of cloud-to-ground (CG) lightning in Belgium are analyzed. Based on data from the European Cooperation for Lightning Detection (EUCLID) network, spanning a period of 10 years between 2004 and 2013, mean CG flash densities vary between 0.3 km−2 yr−1 in the west up to 2.4 km−2 yr−1 toward the east of Belgium, with an average flash density of 0.7 km−2 yr−1. The same behavior is found in terms of thunderstorm days and hours, where in the east most of the activity is observed, with a drop-off toward the coast. The majority of lightning activity takes place in the summer months between May and August, accounting for nearly 90% of the total activity. Furthermore, the thunderstorm season reaches its highest activity in July in terms of CG detections, while the diurnal cycle peaks between 1500 and 1600 UTC. A correlation is found between the estimated peak currents and altitude, with on average higher absolute peak currents at lower elevations and vice versa. In addition, a cell tracking algorithm is applied to the data to monitor the behavior of the individual cells. It is found that the lightning cells travel at an average speed of about 25 km h−1, with a preferred northeasterly direction of movement. At last, CG flash rates are strongly related to the cell area.

scholarly journals Diurnal Variations of NLDN-Reported Cloud-to-Ground Lightning in the United States

2014 ◽  
Vol 142 (3) ◽  
pp. 1037-1052 ◽  
Author(s):  
Ronald L. Holle
Keyword(s):  
United States ◽  
The United States ◽  
Maximum Activity ◽  
Lightning Flash ◽  
Diurnal Changes ◽  
Lightning Detection ◽  
Cloud To Ground Lightning ◽  
Local Mean ◽  
Composite Maps ◽  
Mean Time

Abstract National maps of cloud-to-ground lightning flash density (in flashes per square kilometer per year) for one or more years have been produced since the National Lightning Detection Network (NLDN) was first deployed across the contiguous United States in 1989. However, no single publication includes maps of cloud-to-ground flash density across the domain and adjacent areas during the entire diurnal cycle. Cloud-to-ground lightning has strong and variable diurnal changes across the United States that should be taken into account for outdoor lightning-vulnerable activities, particularly those involving human safety. For this study, NLDN cloud-to-ground flash data were compiled in 20 km by 20 km grid squares from 2005 to 2012 for the lower 48 states. A unique feature of this study is that maps were prepared to coincide with local time, not time zones. NLDN flashes were assigned to 2-h time periods in 5° longitude bands. Composite maps of the 2-h periods with the most lightning in each grid square were also prepared. The afternoon from 1200 to 1800 local mean time provides two-thirds of the day’s lightning. However, lightning activity starts before noon over western mountains and onshore along the Atlantic and Gulf of Mexico coasts. These areas are where recurring lightning-vulnerable recreation and workplace activities should expect the threat at these times, rather than view them as an anomaly. An additional result of the study is the midday beginning of lightning over the higher terrain of the western states, then the maximum activity moves steadily eastward. These storms pose a threat to late-afternoon and evening recreation. In some Midwest and plains locations, lightning is most frequent after midnight.

scholarly journals Radar-Based Automatic Identification and Quantification of Weak Echo Regions for Hail Nowcasting

Atmosphere ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 325 ◽  
Author(s):  
Junzhi Shi ◽  
Ping Wang ◽  
Di Wang ◽  
Huizhen Jia
Keyword(s):  
Cross Section ◽  
Real Data ◽  
Vital Role ◽  
Vertical Cross Section ◽  
Automatic Identification ◽  
Identification Algorithm ◽  
Critical Success ◽  
Radar Echo ◽  
Convective Cells ◽  
Critical Success Index

The identification of some radar reflectivity signatures plays a vital role in severe thunderstorm nowcasting. A weak echo region is one of the signatures that could indicate updraft, which is a fundamental condition for hail production. However, this signature is underutilized in automatic forecasting systems due to the lack of a reliable detection method and the uncertain relationships between different weak echo regions and hail-producing thunderstorms. In this paper, three algorithms related to weak echo regions are proposed. The first is a quasi-real-time weak echo region morphology identification algorithm using the radar echo bottom height image. The second is an automatic vertical cross-section-making algorithm. It provides a convenient tool for automatically determining the location of a vertical cross-section that exhibits a visible weak echo region to help forecasters assess the vertical structures of thunderstorms with less time consumption. The last is a weak echo region quantification algorithm mainly used for hail nowcasting. It could generate a parameter describing the scale of a weak echo region to distinguish hail and no-hail thunderstorms. Evaluation with real data of the Tianjin radar indicates that the critical success index of the weak echo region identification algorithm is 0.61. Statistics on these data also show that when the weak echo region parameters generated by the quantification algorithm are in a particular range, more than 85% of the convective cells produced hail.

scholarly journals The Daily Cloud-to-Ground Lightning Flash Density in the Contiguous United States and Finland

2011 ◽  
Vol 139 (5) ◽  
pp. 1323-1337 ◽  
Author(s):  
Antti Mäkelä ◽  
Pekka Rossi ◽  
David M. Schultz
Keyword(s):  
United States ◽  
Detection Efficiency ◽  
Quantitative Measure ◽  
The United States ◽  
Lightning Flash ◽  
Upper Midwest ◽  
Lightning Detection ◽  
Operational Forecasting ◽  
Central United States ◽  
Cloud To Ground Lightning

A method is developed to quantify thunderstorm intensity according to cloud-to-ground lightning flashes (hereafter ground flashes) determined by a lightning-location sensor network. The method is based on the ground flash density ND per thunderstorm day (ground flashes per square kilometer per thunderstorm day) calculated on 20 km × 20 km fixed squares. Because the square size roughly corresponds to the area covered by a typical thunderstorm, the flash density for one square defines a unit thunderstorm for the purposes of this study. This method is tested with ground flash data obtained from two nationwide lightning-location systems: the National Lightning Detection Network (NLDN) in the contiguous United States and the portion of the Nordic Lightning Information System (NORDLIS) in Finland. The distribution of daily ground flash density ND is computed for all of Finland and four 800 000 km2 regions in the United States (identified as western, central, eastern, and Florida). Although Finland and all four U.S. regions have median values of ND of 0.01–0.03 flashes per square kilometer per thunderstorm day—indicating that most thunderstorms produce relatively few ground flashes regardless of geographical region—the most intense 1% of the storms (as measured by the 99th percentiles of the ND distributions within each region) show much larger differences among regions. For example, the most intense 1% of the ND distributions is 1.3 flashes per square kilometer per thunderstorm day in the central U.S. region, but only 0.2 flashes per square kilometer per thunderstorm day in Finland. The spatial distribution of the most intense 1% of the ND distributions illustrates that the most intense thunderstorm days occur in the central United States and upper Midwest, which differs from the maxima of the average annual flash density NA and the number of thunderstorm days TD, both of which occur in Florida and along the coast of the Gulf of Mexico. This method for using ND to quantify thunderstorm intensity is applicable to any region as long as the detection efficiency of the lightning-location network is high enough or known. This method can also be employed in operational forecasting to provide a quantitative measure of the lightning intensity of thunderstorms relative to climatology.

scholarly journals Cell-tracking with lightning data from LINET

2008 ◽  
Vol 17 ◽  
pp. 55-61 ◽  
Author(s):  
H. D. Betz ◽  
K. Schmidt ◽  
W. P. Oettinger ◽  
B. Montag
Keyword(s):  
Cell Tracking ◽  
Planning Stage ◽  
Lightning Detection ◽  
University Of Munich ◽  
A Cell ◽  
Storm Cells ◽  
Total Lightning ◽  
Convective Cells ◽  
The University ◽  
Tracking Module

Abstract. A new lightning detection network (LINET) has been developed at the University of Munich, which locates and reports both cloud discharges and cloud-to-ground strokes with high accuracy. The network started operation in May 2006; since then lightning data for Europe are being delivered to many scientific groups, and to the German Weather Service (DWD) on an operational basis (powered by nowcast GmbH, Germany). Using about 90 lightning sensors in 17 countries, an area from longitude 10° W–25° E to latitude 35° N–65° N is covered. Further expansion is in the planning stage with the aim to attain higher efficiency for Mediterranean storms. The total lightning capability, not readily available otherwise in large areas, is particularly helpful because it can provide useful information about the development of severe weather and strong storm cells. A cell-tracking module has been developed that allows the investigation of lightning parameters for specific convective cells. Present efforts are devoted to the question for what kind of storms and to what extent lightning-based cell tracking allows improved nowcasting. Numerous case studies have been carried out and typical examples will be presented.

scholarly journals Cloud-to-Ground Lightning Flash Parameters Associated with Heavy Rainfall Alarms in the Denver, Colorado, Urban Drainage and Flood Control District ALERT Network

2006 ◽  
Vol 134 (9) ◽  
pp. 2566-2580 ◽  
Author(s):  
S. Jeffrey Underwood
Keyword(s):  
Heavy Rainfall ◽  
Flood Control ◽  
Rainfall Rate ◽  
Urban Drainage ◽  
Lightning Flash ◽  
Flash Duration ◽  
Lower Elevation ◽  
Lightning Detection ◽  
Cloud To Ground Lightning ◽  
The Mean

Abstract Rainfall data from the Denver, Colorado, Urban Drainage and Flood Control District Automated Local Evaluation in Real Time (ALERT) network were used to identify heavy rainfall alarms for the period 1999–2003. Twenty-nine heavy rainfall-rate alarms were identified. Cloud-to-ground (CG) lightning flash data from the National Lightning Detection Network (NLDN) were analyzed for the 90 min prior to each heavy rainfall alarm. Spatial patterns from NLDN data were extracted using a point-polygon topology developed with basic Geographic Information System procedures. The information extracted from the polygons was used to calculated summary statistics for rainfall rates, CG flash rates, and CG flash duration. Heavy rainfall episodes were divided into two groups based on latitude, longitude, and elevation. Heavy rainfall episodes in the higher elevations of the study area produced an average of 29 mm of rainfall per episode and 1095 CG flashes in the 90 min prior to the rainfall-rate alarm. Only five polygons, all closely proximal to the alarm sites, produced significant CG flash rates prior to the rainfall alarms, and areas with CG flash durations greater than 25 min were clustered near the rainfall-rate alarm sites. In the second group (the lower elevation stations) the mean event produced a total of 33 mm of rainfall and 1182 CG flashes during the 90 min prior to the rainfall alarm. Four polygons saw consistent CG flash rates in the 90 min prior to the heavy rainfall alarms and CG flash duration was at its greatest in areas just west of the ALERT stations.

scholarly journals A Cloud-to-Ground Lightning Climatology for Poland

2015 ◽  
Vol 143 (11) ◽  
pp. 4285-4304 ◽  
Author(s):  
Mateusz Taszarek ◽  
Bartosz Czernecki ◽  
Aneta Kozioł
Keyword(s):  
Annual Number ◽  
Lightning Flash ◽  
Grid Cells ◽  
Lake District ◽  
Negative Current ◽  
Lightning Detection ◽  
Cloud To Ground Lightning ◽  
The Mean ◽  
The Baltic ◽  
Cg Lightning

Abstract This research focuses on the climatology of cloud-to-ground (CG) lightning flashes based on PERUN lightning detection network data from 2002 to 2013. To present various CG lightning flash characteristics, 10 km × 10 km grid cells are used, while for estimating thunderstorm days, circles with radii of 17.5 km in the 1 km × 1 km grid cells are used. A total of 4 328 892 CG lightning flashes are used to analyze counts, density, polarity, peak current, and thunderstorm days. An average of 151 days with thunderstorm (appearing anywhere in Poland) occurs each year. The annual number of days with thunderstorms increases southeasterly from the coast of the Baltic Sea (15–20 days) to the Carpathian Mountains (30–35 days). The mean CG lightning flash density varies from 0.2 to 3.1 flashes km−2 yr−1 with the highest values in the southwest–northeast belt from Kraków-Częstochowa Upland to the Masurian Lake District. The maximum daily CG lightning flash density in this region amounted to 9.1 km−2 day−1 (3 July 2012). The monthly variation shows a well-defined thunderstorm season extending from May to August with July as the peak month. The vast majority of CG lightning flashes were detected during the daytime (85%) with a peak at 1400 UTC and a minimum at 0700 UTC. Almost 97% of all CG lightning flashes in the present study had a negative current, reaching the highest average monthly values in February (55 kA) and the lowest in July (24 kA). The percentage of positive CG lightning flashes was the lowest during the summer (2%–3%) and the highest during the winter (10%–20%).

Summertime Cloud-to-Ground Lightning Activity around Major Midwestern Urban Areas

1995 ◽  
Vol 34 (7) ◽  
pp. 1633-1642 ◽  
Author(s):  
Nancy E. Westcott
Keyword(s):  
Urban Areas ◽  
Cloud Condensation Nuclei ◽  
Thunderstorm Activity ◽  
Lightning Activity ◽  
Lightning Flash ◽  
Storm Activity ◽  
Topographic Features ◽  
Activity Frequency ◽  
Lightning Detection ◽  
Cloud To Ground Lightning

Abstract Cloud-to-ground lightning flash data collected by the National Lightning Detection Network were analysed in and around 16 central U.S. cities for the period 1989–92. Lightning data are well suited to study storm activity in and around large urban areas since their continuity and coverage in space and time is superior to historical, spatially limited records of thunderstorm activity. Frequency of cloud-to-ground lightning flashes (of negative and positive polarity) in the area immediately upwind, within, and immediately downwind of the cities were compared. An enhancement of lightning frequency on the order of 40%–85% was found over and downwind of many of these cities. A number of possible urban-related causal factors were examined including effects of increased urban concentrations of cloud condensation nuclei, urban population and size, and the presence of distinct topographic features in and around the cities. Various factors, physical and anthropogenic, appeared to interact in diverse ways to account for changes in lightning flash frequency. The enhancement of lightning activity was largest during the afternoon hours when the urban–rural temperature differences are usually smallest, but when the atmosphere is generally the most unstable and when there is often a maximum in convective activity. The spatial distribution of the first 50 lightning flashes from each storm suggested that the urban area did not initiate new lightning storms. Thus, the overall results suggested that existing thunderstorms were the most strongly affected.

scholarly journals Where Is the Real Cloud-to-Ground Lightning Maximum in North America?

2005 ◽  
Vol 20 (2) ◽  
pp. 125-133 ◽  
Author(s):  
Martin J. Murphy ◽  
Ronald L. Holle
Keyword(s):  
Detection Efficiency ◽  
Local Maximum ◽  
Propagation Model ◽  
Model Parameters ◽  
Lightning Flash ◽  
Lightning Detection ◽  
Cloud To Ground Lightning ◽  
Northwestern Mexico ◽  
Signal Normalization ◽  
Relative Detection

Abstract A local maximum in cloud-to-ground (CG) lightning flash density over northwestern Mexico as measured by the U.S. National Lightning Detection Network is examined in detail. Corrections are derived for the relative detection efficiency of the network in this region that is outside the perimeter of the sensors. The need to adjust the parameters of the signal normalization model used for the network is also documented. New propagation model parameters are employed to derive relative detection efficiency corrections for northwestern Mexico and these are then used to show that the actual CG flash density over the region significantly exceeds that observed in Florida, the area with the highest flash density within the perimeter of the network.

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