An official website of the United States government
Abstract Two dimensional (2‐D) histogram distributions of lightning flashes relative to radar reflectivity and altitude were created using a total of 41,180 intercloud/intracloud (IC) flashes, 3,326 cloud‐to‐ground (CG) flashes, and 4,349 hybrid (HY) flashes that originated in multicells; 111,479 IC flashes, 8,588 CG flashes, and 11,699 HY flashes that originated in mesoscale convective systems; and 91,283 IC flashes, 3,023 CG flashes, and 7,872 HY flashes that originated in supercells that occurred over northern Alabama and southern Tennessee. It was shown that although CG flashes initiate and propagate at the same altitude irrespective of storm type, IC flashes could have differences of up to 10 °C, while for HY flashes these differences increased to up to 20 °C relative to storm type. Further, IC, CG, and HY flashes propagated in lower reflectivities than where they initiated, while CG flashes initiated and propagated within higher reflectivities than IC and HY flashes. HY flashes were also twice as large as IC flashes and ~40% larger than CG flashes, and flashes that originated in mesoscale convective systems had larger overall sizes as compared to multicells and supercells. When comparing the new 2‐D histogram distributions to the legacy distributions used for the calculation of lightning‐produced nitrogen oxides (LNOx), it was shown that the new distributions perform much better, with higher Pearson product moment correlation coefficient values and much lower root‐mean‐square errors. These new distributions are thus more appropriate to use when modeling LNOx and will lead to more accurate LNOx estimations than using the legacy distributions.
more »
« less
Radar Reflectivity and Altitude Distributions of Lightning Flashes as a Function of Three Main Storm Types
Abstract In an effort to improve our knowledge on the horizontal and vertical distribution of lightning initiation and propagation, ~500 multicells (producing a total of 72,619 flashes), 27 mesoscale convective systems (producing 214,417 flashes) and 23 supercells (producing 169,861 flashes) that occurred over northern Alabama and southern Tennessee were analyzed using data from the North Alabama Lightning Mapping Array and the Multi‐Radar Multi‐Sensor suite. From this analysis, two‐dimensional (2‐D) histograms of where flashes initiated and propagated relative to radar reflectivity and altitude were created for each storm type. The peak of the distributions occurred between 8.0 and 10.0 km (−24.0 to −38.5 °C) and between 30 and 35 dBZfor flashes that initiated within multicellular storms. For flashes that initiated within mesoscale convective systems, these peaks were 8.0–9.0 km (−27.1 to −34.6 °C) and 30–35 dBZ, respectively, and for supercells, they were 10.0–12.0 km (−42.6 to −58.1 °C) and 35–40 dBZ, respectively. The 2‐D histograms for the flash propagations were slightly different than for the flash initiations and showed that flashes propagated in lower reflectivities as compared to where they initiated. The 2‐D histograms were also compared to test cases; the root‐mean‐square errors and the Pearson product moment correlation coefficient (R) were calculated with several of the comparisons havingRvalues >0.7 while the root‐mean‐square errors were always ≤0.017 (≤10%), irrespective of storm type. Finally, the mean flash sizes for the multicell, mesoscale convective system, and supercell flashes were 8.3, 9.9, and 7.4 km, respectively.
more »
« less
- Award ID(s):
- 1063573
- PAR ID:
- 10459279
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 123
- Issue:
- 22
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Global satellite studies show a maximum in deep convection and lightning downstream of the Andes in subtropical South America. The Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign was designed to investigate the physical processes that contribute to the rapid development of deep convection and mesoscale convective systems (MCSs) in Argentina. A lightning mapping array (LMA) was deployed to Argentina as part of RELAMPAGO to collect lightning observations from extreme storms in the region. This study combines lightning data from the LMA and the Geostationary Lightning Mapper onboardGOES‐16with 1‐km gridded radar data to examine the electrical characteristics of a variety of convective storms throughout their life cycle observed during RELAMPAGO. Results from the full campaign show 48% of flashes are associated with deep convection that occurs along the eastern edge of the Sierras de Córdoba (SDC) overnight. These flashes are 65 km2smaller on average compared to stratiform flashes, which occur most frequently 50–100 km east of the SDC in the early morning hours, consistent with the upscale growth of MCSs off the terrain. Analysis of the 13–14 December MCS shows that sharp increases in flash rates correspond to deep and wide convective cores that have high graupel and hail mass, 35‐dBZ volume, and ice water path. This work validates previous satellite studies of lightning in the region, but also provides higher spatial and temporal resolution information across the convective life cycle that has not been available in previous studies.more » « less
-
Abstract A positive cloud‐to‐ground (+CG) lightning flash containing a single stroke with a peak current of approximately +310 kA followed by a long continuing current triggered seven upward lightning flashes from tall structures. The flashes were observed on 4 June 2016 at the Tall Object Lightning Observatory in Guangzhou, Guangdong Province, China. The optical and electric field characteristics of these flashes were analyzed using synchronized two‐station data from two high‐speed video cameras, one total‐sky lightning channel imager, two lightning channel imagers, and two sets of slow and fast electric field measuring systems. Three upward flashes were initiated sequentially in the field of view of high‐speed video cameras. One of them was initiated approximately 0.35 ms after the return stroke of +CG flash from the Canton Tower, the tallest structure within a 12‐km radius of the +CG flash, while the other two upward flashes were initiated from two other, more distant tall objects, approximately 18 ms after the +CG flash stroke. The initiation of the latter two upward flashes could be caused by the combined effect of the return stroke of +CG flash, its associated continuing current, and K process in the cloud. Each of these three upward flashes contained multiple downward leader/upward return stroke sequences, with the first leader/return stroke sequence of the second and third flashes occurring only after the completion of the last leader/return stroke sequence of the preceding flash. The total number of strokes in the three upward flashes was 13, and they occurred over approximately 1.5 s.more » « less
-
Abstract The Córdoba Argentina Marx Meter Array (CAMMA), consisting of 10 second‐generation Huntsville Alabama Marx Meter Array (HAMMA 2) sensors, operated at Córdoba, Argentina, during the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign in late 2018. Initial results obtained from the campaign demonstrate that the new sensor is able to provide a significantly more detailed depiction of various lightning processes than its first generation. The lightning flashes mapped by the CAMMA and a colocated Lightning Mapping Array (LMA) were compared. The overall flash structures mapped by the CAMMA and the LMA look similar for most of the flashes. However, comparisons at smaller time scale show that the majority of CAMMA and LMA sources are not concurrent, indicating that unmatched sources were possibly due to different physical processes in leader propagation dominating different frequencies and differences in data processing and location techniques.more » « less
-
Polarimetric and Electrical Structure of the 19 May 2013 Edmond–Carney, Oklahoma, Tornadic SupercellAbstract We demonstrate the utility of transient polarimetric signatures (ZDRandKDPcolumns, a proxy for surges in a thunderstorm updraft) to explain variability in lightning flash rates in a tornadic supercell. Observational data from a WSR-88D and the Oklahoma lightning mapping array are used to map the temporal variance of polarimetric signatures and VHF sources from lightning channels. It is shown, via three-dimensional and cross-sectional analyses, that the storm was of inverted polarity resulting from anomalous electrification. Statistical analysis confirms that mean flash area in theZDRcolumn region was 10 times smaller than elsewhere in the storm. On an average, 5 times more flash initiations occurred withinZDRcolumn regions, thereby supporting existing theory of an inverse relationship between flash initiation rates and lightning channel extent. Segmentation and object identification algorithms are applied to gridded radar data to calculate metrics such as height, width, and volume ofZDRandKDPcolumns. Variability in lightning flash rates is best explained by the fluctuations inZDRcolumn volume with a Spearman’s rank correlation coefficient value of 0.72. The highest flash rates occur in conjunction with the deepestZDRcolumns (up to 5 km above environmental melting level) and largest volumes ofZDRcolumns extending up to the −20°C level (3 km above the melting level). Reduced flash rates toward the end of the analysis are indicative of weaker updrafts manifested as lowZDRcolumn volumes at and above the −10°C level. These findings are consistent with recent studies linking lightning to the interplay between storm dynamics, kinematics, thermodynamics, and precipitation microphysics.more » « less
