Theory and Observations of Controls on Lightning Flash Size Spectra

Carey

Weather and Forecasting

et al. 2017

Thirty-nine thunderstorms are examined using multiple-Doppler, polarimetric and total lightning observations to understand the role of mixed phase kinematics and microphysics in the development of lightning jumps. This sample size is larger than those of previous studies on this topic. The principal result of this study is that lightning jumps are a result of mixed phase updraft intensification. Larger increases in intense updraft volume (≥ 10 m s −1 ) and larger changes in peak updraft speed are observed prior to lightning jump occurrence when compared to other non-jump increases in total flash rate. Wilcoxon-Mann-Whitney Rank Sum testing yields p-values ≤0.05, indicating statistical independence between lightning jump and non-jump distributions for these two parameters. Similar changes in mixed phase graupel mass magnitude are observed prior to lightning jumps and non-jump increases in total flash rate. The p-value for graupel mass change is p=0.096, so jump and non-jump distributions for graupel mass change are not found statistically independent using the p=0.05 significance level. Timing of updraft volume, speed and graupel mass increases are found to be 4 to 13 minutes in advance of lightning jump occurrence. Also, severe storms without lightning jumps lack robust mixed phase updrafts, demonstrating that mixed phase updrafts are not always a requirement for severe weather occurrence. Therefore, the results of this study show that lightning jump occurrences are coincident with larger increases in intense mixed phase updraft volume and peak updraft speed than smaller non-jump increases in total flash rate.

Section: Discussion a The Importance Of Peak Updraft Speed And 10 M mentioning

confidence: 99%

Kinematic and Microphysical Significance of Lightning Jumps versus Nonjump Increases in Total Flash Rate

Carey

Weather and Forecasting

et al. 2017

“…Misplaced or mistimed sources are hard to remedy by flash clustering algorithms (McCaul Jr et al, 2005) and the remaining residual noise should be avoided to correctly estimate flash dimensions. Bruning and MacGorman (2013) calculated the flash horizontal extension by means of a convex hull function (plan view). The convex hull is the polygon produced by allowing a rubber band to contract on all the points constituting the flash (Devadoss and O'Rourke, 2011).…”

Section: Methodsmentioning

confidence: 99%

“…The convex hull is the polygon produced by allowing a rubber band to contract on all the points constituting the flash (Devadoss and O'Rourke, 2011). The convex hull allows defining the geometry instead of imposing an assumed form (Bruning and MacGorman, 2013). However, the polygon defined by the convex hull may have a complicated shape and may contain a lot of nodes, including noisy sources.…”

Section: Methodsmentioning

confidence: 99%

“…Such a measurement is important to estimate NOx per flash among other lightning properties. Bruning and MacGorman (2013) demonstrated studying LMA data that the extension of lightning is related to the storm intensity. They have shown that lightning flashes near strong updrafts, tend to be more frequent and smaller whereas those occurring far from strong vertical drafts were larger and less frequent.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Spatio-temporal dimension of lightning flashes based on three-dimensional Lightning Mapping Array

López

Pineda

Montanyà

et al. 2017

Atmospheric Research

ABSTRACT3D mapping system like the LMA -Lightning Mapping Array -are a leap forward in lightning observation. LMA measurements has lead to an improvement on the analysis of the fine structure of lightning, allowing to characterize the duration and maximum extension of the cloud fraction of a lightning flash. During several years of operation, the first LMA deployed in Europe has been providing a large amount of data which now allows a statistical approach to compute the full duration and horizontal extension of the in-cloud phase of a lightning flash. The "Ebro Lightning Mapping Array" (ELMA) is used in the present study. Summer and winter lighting were analyzed for seasonal periods (Dec-Feb and Jun-Aug). A simple method based on an ellipse fitting technique (EFT) has been used to characterize the spatio-temporal dimensions from a set of about 29,000 lightning flashes including both summer and winter events. Results show an average lightning flash duration of 440 ms (450 ms in winter) and a horizontal maximum length of 15.0 km (18.4 km in winter). The uncertainties for summer lightning lengths were about ± 1.2 km and ± 0.7 km for the mean and median values respectively. In case of winter lightning, the level of uncertainty reaches up to 1 km and 0.7 km of mean and median value. The results of the successful correlation of CG discharges with the EFT method, represent 6.9% and 35.5% of the total LMA flashes detected in summer and winter respectively. Additionally, the median value of lightning lengths calculated through this correlative method was approximately 17 km for both seasons. On the other hand, the highest median ratios of lightning length to CG discharges in both summer and winter were reported for positive CG discharges.

“…Both the LMA and GLM provide spatial and temporal information for each lightning flash, which can be used to derive a flash's footprint (e.g., Bruning and MacGorman 2013, Calhoun et al 2013, Schultz et al 2015). An example of how a lightning flash observed by NALMA and the NLDN might appear in the GLM framework is found in Fig.…”

Section: Translating Findings To Glm's Resolutionmentioning

confidence: 99%

Lightning Decision Support Using VHF Total Lightning Mapping and NLDN Cloud-to-Ground Data in North Alabama

Schultz¹,

Stano²,

Meyer³

et al. 2017

J. Operational Meteor.