Lightning! Memphis AMS/NWA Chapter meeting March 23, 2010

Overview History of electrification History of electrification Charge development and lightning formation Charge development and lightning formation Measurement tools Measurement tools National Lightning Detection Network National Lightning Detection Network Lightning Mapping Arrays Lightning Mapping Arrays Satellite Satellite Current research Current research Severe weather Severe weather Lightning warnings/cessation Lightning warnings/cessation

Lightning: A brief history Benjamin Franklin performed the first study of lightning in September Kite experiment May 10, 1752 This experiment was successfully repeated in 1752 by French scientist Thomas Francois D'Alibard In July 1753 Swedish scientist G. W. Richmann was killed when trying to recreate the Franklin experiment. Little was done between the late 1700s until the early 1900s Image adapted from MacGorman and Rust (1998) The Electrical Nature of Storms

Lightning: a brief history C.T.R. Wilson was the first to use electric field measurements to estimate the structure of thunderstorm charges involved in lightning discharges. C.T.R. Wilson was the first to use electric field measurements to estimate the structure of thunderstorm charges involved in lightning discharges. Wilson formulated the hypothesis that a thunderstorm consisted of a dipole Wilson formulated the hypothesis that a thunderstorm consisted of a dipole Wilson also won the Nobel Peace Prize for the creation of his cloud chamber Wilson also won the Nobel Peace Prize for the creation of his cloud chamber Lightning research took off in the early 1960s with the development of the space program Lightning research took off in the early 1960s with the development of the space program Image adapted from

Charge Development The non-inductive charging mechanism primarily responsible for thunderstorm charging. The non-inductive charging mechanism primarily responsible for thunderstorm charging. Temperature difference causes charge difference Temperature difference causes charge difference Collisions cause charge separation Collisions cause charge separation Sign of charge transferred depends on: Sign of charge transferred depends on: temperature temperature effective liquid water contents effective liquid water contents rime accretion rate rime accretion rate relative velocity between particles relative velocity between particles Figure above adapted from Saunders (1993) Combination of results from Takahashi (1978) and Saunders et al. (1991)

Lightning Formation 3/6+ Step process 3/6+ Step process Corona Corona Stepped Leader Stepped Leader 50 m jumps, tip of leader is corona point 50 m jumps, tip of leader is corona point Cloud to Ground also includes Cloud to Ground also includes Upward Leader Upward Leader Junction process Junction process Return stroke Return stroke dart leader dart leader dart stepped leader dart stepped leaderVIDEO(S) Interferometer measurement of in cloud lightning. Adapted from Shao and Krehbiel (1996)

Lightning Measurements

National Lightning Detection Network First developed in the early 1980s Originally used TOA system (LPATS) Direction finder network created by early 1990s 2 antennas Companies merged, and merged systems, and now this is owned by Vaisala, Inc. New sensor is a combination of both IMPACT sensor (left) Images courtesy

3-D Lightning Mapping Above – The Northern Alabama 3-D VHF Lightning Mapping Array VHF antenna locations (green dots). Image provided by the NASA SPoRT (Short-term Prediction Research and Transition Center) website. ( Adapted from Thomas et al. (2004) depicting a lightning flash in space and time. Cool colors represent the early parts of the flash, while warmer colors indicate flash propagation in the latter part of the flashes history Lightning mapping arrays measure the electrical breakdown process using VHF sources in 80 μs intervals to detect lightning in three dimensions Operates using TV channel 5 (76-82 MHz) Accuracy out to 150 km, <50 m

LMA Flash examples Movies taken from: March , 0809 UTCMarch , 0819 UTC

Precursors to the Satellite Era Video taken from the space shuttle over Argentina. Courtesy Dr. William Koshak, MSFC U2 observation of a thunderstorm over Georgia, in June Vonnegut et al. (1989)

Satellite Observations Lightning can be observed from space Lightning can be observed from space Two satellites have been used to observe lightning Two satellites have been used to observe lightning Tropical Rainfall Measuring Mission Tropical Rainfall Measuring Mission Optical Transient Detector Optical Transient Detector Uses a thin oxygen line to observe lightning flashes Uses a thin oxygen line to observe lightning flashes Future real time observations of total lightning will be on the GOES-R satellite Future real time observations of total lightning will be on the GOES-R satellite (Images courtesy Tropical Rainfall Measuring Mission Satellite Total lightning observed by TRMM

Part 3: Current Research KBMX RSA 68 km KGWX UAH/NSSTC THOR Center and Hazardous Weather Testbed MIPS/NSSTC ARMOR KHTX 75 DD lobe 1 km Res. 1.5 km Res. LMA m LMA Antenna NEXRAD ARMOR MIPS Profiler MAX ? MAX 2144

Correlating Lightning to Severe Weather Goodman et al demonstrated that total lightning peaked prior to the onset of a microburst Goodman et al demonstrated that total lightning peaked prior to the onset of a microburst Williams et al showed that the peak total flash rate correlated with the maximum vertical extent of pulse thunderstorms, and preceded maximum outflow velocity by several minutes Williams et al showed that the peak total flash rate correlated with the maximum vertical extent of pulse thunderstorms, and preceded maximum outflow velocity by several minutes Adapted from Williams et al. (1989) Adapted from Goodman et al. (1988)

Previous Work Williams et al. (1999) once again illustrates the usefulness of total lightning data in determination of storm severity in Florida thunderstorms. Williams also proposed 60 flashes min -1 or greater for separation between severe and non-severe thunderstorms. Adapted from Williams et al. (1999)

Overall Goals – Lightning Jump Algorithm 1. Build on the lightning jump framework set through previous studies. 2. Understand what typically occurs in non-severe convection with respect to increases in lightning. 3. Ultimately develop a lightning jump algorithm for use on the Geostationary Lightning Mapper (GLM) Also for NWS offices with ground based lightning mapping networks available. Adapted from Williams et al. (1999)

Severe Weather Examples April 4, 2007, UTCSeptember 25, UTC

Null Examples/ False Alarms June 14, 2005 LMA Source Data Z 19 June 2007

Lightning Jump Algorithm Update 367 thunderstorms analyzed so far from 367 thunderstorms analyzed so far from 3 different regions of the country 3 different regions of the country 111 severe, 256 non severe 111 severe, 256 non severe Best skill from the 2 sigma configuration Best skill from the 2 sigma configuration NWS skill scores for all severe weather (80-90% POD; FAR ~48%) NWS skill scores for all severe weather (80-90% POD; FAR ~48%) Average Peak flash rate of non severe thunderstorms about 10 flashes per minute Average Peak flash rate of non severe thunderstorms about 10 flashes per minute Next steps: Next steps: Look at other regions of the country Look at other regions of the country Examine warning summaries from NWS to compare to jump signatures Examine warning summaries from NWS to compare to jump signatures Explore combinations of algorithms to see if there is any improvement in the skill scores Explore combinations of algorithms to see if there is any improvement in the skill scores Gatlin 2 Sigma 3 Sigma Threshold 4 Threshold 5 POD FAR CSI HSS

Lightning Warning Products D. Buechler, NASA, MSFC/UAHuntsville

Lightning Cessation

Polarimetric Radar 1.Reflectivity factor Z at horizontal (Z h ) or vertical (Z v ) polarization [Conventional radar measure] - Measure of drop size and concentration; Most sensitive to drop SIZE (D 6 ) 2.Differential reflectivity Z DR a ratio of returned power: (Z h /Z v ) - Measure of median drop diameter→ SIZE/SHAPE - Useful for rain / hail / snow discrimination→ SIZE/SHAPE 3.Propagation differential phase,  DP, and from it, specific propagation differential phase KDP  (k h – k v ) - Measure of water content and drop size→ NUMBER/SHAPE - Immune to radar calibration, attenuation, partial beam blockage 4.Correlation coefficient ρ hv - Indicator of mixed precipitation → SHAPE/PHASE/CANTING (Depolarization) - Useful for identifying non-meteorological scatterers too! Advantages: Better description of various particle types/shapes in a given volume Determine size distribution- more accurate rain rates (improved QPE) Hydrometeor ID and non-meteorological scatterers (clutter!) Consistent calibration Z h, k h Z v, k v We need the measurement in H and V directions! Walter A. Petersen NASA MSFC VP-61 Variables……..

Background Past research has shown strong evidence for ice crystal orientation signatures in polarimetric radar [differential phase] observations of thunderstorms (e.g., Hendry and McCormick 1976, 1979; Hendry and Antar 1982; Krehbiel et al. 1991, 1992, 1996; Metcalf, 1992, 1995; Caylor and Chandrasekar 1996; Galloway et al. 1997; Scott et al. 2001; Marshall et al. 2009). Past research has shown strong evidence for ice crystal orientation signatures in polarimetric radar [differential phase] observations of thunderstorms (e.g., Hendry and McCormick 1976, 1979; Hendry and Antar 1982; Krehbiel et al. 1991, 1992, 1996; Metcalf, 1992, 1995; Caylor and Chandrasekar 1996; Galloway et al. 1997; Scott et al. 2001; Marshall et al. 2009). Theoretical work by Weinheimer and Few (1987) demonstrated that ice crystals up to 1-2 mm could be vertically aligned by strong vertical electric fields (E- fields) of about kV m -1. Theoretical work by Weinheimer and Few (1987) demonstrated that ice crystals up to 1-2 mm could be vertically aligned by strong vertical electric fields (E- fields) of about kV m -1. Strong motivation for our ongoing work is provided by Krehbiel et al. (1993): Strong motivation for our ongoing work is provided by Krehbiel et al. (1993): “[polarimetric radar] signatures have been found to provide an excellent indicator of the potential for lightning in a storm and we have used them to predict the occurrence of numerous lightning discharges. The [polarimetric] measurements have also been used to detect the initial electrification of storms and to determine when a storm is finished producing lightning.” Radar differential phase (specific differential phase, K dp, and its integral  dp or PHIDP) is currently measured by many research (e.g., UAH-NASA ARMOR C-band, UAH MAX X-band) and operational (e.g., new 45WS CCAFS-KSC Radtec TDR 43 ‑ 250 C-band) radars. Radar differential phase (specific differential phase, K dp, and its integral  dp or PHIDP) is currently measured by many research (e.g., UAH-NASA ARMOR C-band, UAH MAX X-band) and operational (e.g., new 45WS CCAFS-KSC Radtec TDR 43 ‑ 250 C-band) radars. L. D. Carey, ESSC, ST2009

6.2 km 7.2 km  DP   6.2 km 7.2 km  DP   Height Time Sector scans: Examine time and height changes in ice orientation (change of  DP with range-red circle) in a lightning-producing cloud. [UAH X-band dual-pol data from August 18, 2009] UTC 1632 UTC Before flashAfter flash

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