7.3 Recent Improvements in Lightning Reporting at 45TH Weather Squadron (original) (raw)
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Recent Improvements in Lightning Reporting at 45 TH Weather Squadron
2010
The 45th Weather Squadron (45 WS) is the United States (U.S.) Air Force unit that provides weather support to America’s space program at Cape Canaveral Air Force Station (CCAFS), National Aeronautics and Space Administration (NASA) Kennedy Space Center (KSC), and Patrick AFB (PAFB). The weather requirements of the space program are very stringent (Harms et al., 1999). In addition, the weather in east central Florida is very complex. This is especially true of summer thunderstorms and associated hazards. Central Florida is ‘Lightning Alley’, the area of highest lightning activity in the U.S. (Huffines and Orville, 1999). The 45 WS uses a dense network of various weather sensors to meet the operational requirements in this environment (Roeder et al., 2003). The 45 WS is especially well instrumented with lightning detection sensors. The Four Dimensional Lightning Surveillance System (4DLSS) (Murphy et al., 2008) included a major upgrade to the total lightning detection Lightning Detect...
2010 30th International Conference on Lightning Protection (ICLP), 2010
A new comprehensive lightning instrumentation system has been designed for Launch Complex 39B at the Kennedy Space Center, Florida. This new instrumentation system includes the synchronized recording of six high-speed video cameras, currents through the nine downconductors of the new lightning protection system, four B-dot, 3-axis measurement stations, and five D-dot stations composed of two antennas each. The instrumentation system is composed of centralized transient recorders and digitizers that located close to the sensors in the field. The sensors and transient recorders communicate via optical fiber. The transient recorders are triggered by the B-dot sensors, the E-dot sensors, or the current through the downlead conductors. The high-speed cameras are triggered by the transient recorders when the latter perceives a qualified trigger.
A Review of Operational Lightning Detection: Comparison of Ground vs. Satellite-based Observations
Lightning generated by convective storms, and identified as a formidable hazard to life and property, results from strong storms lofting liquid-phase hydrometeors to high altitudes where freezing occurs and collisions between drops, graupel, and ice crystals lead to electrification. Among the most widely accepted theories of convective storm electrification is the " charge transfer-separation process " by which interaction (esp. collision) between ice crystals and graupel particles result in the establishment and stratification of positive and negative charge centers within the convective cloud, respectively. Differing growth processes between ice crystals (i.e. deposition of water vapor) and graupel (accretion of supercooled water) result in differing molecular structure and electron arrangement, and subsequently, favor the transfer of electrons with negative charge from an ice crystal to a graupel particle. In general, negative charge accumulates in the middle levels of the convective storm cloud, referred to as the " main negative charge " charge center, while positive charge accumulates in the upper layer and anvil (if present) region and is referred to as the " upper positive charge " center. Other secondary charge centers may develop in a convective storm, such as the " lower positive charge " center that results from falling hail, however, the main electric field built within the storm results from the separation of the main negative and upper positive charge centers. When the electric field strength (E) between the storm cloud and the ground eventually increases to the threshold value of electric breakdown potential (3 x 10 9 V/km), a stepped leader, defined as a segmented ionized channel, develops and propagates downward toward the ground in steps of 50 to 100 m length. Upon contact of the stepped leader with the ground, a bright return stroke from the ground to the cloud occurs, in which electrons flow downward from progressively higher levels in the channel. The stepped leader and return stroke comprise the lightning strike. The strike with additional return strokes, triggered by a dart leader, then comprise the cloud-to-ground (CG) lightning flash. Intracloud (IC) lightning discharge between the main negative and upper positive charge centers also results from charge separation and electrical breakdown. Ground-based and satellite-based lightning detection systems often detect both IC and CG lightning flashes, with CG strokes a stronger emitter of low frequency (LF) radiation. Lightning detection systems (LDS) have a vital role in the real-time identification of the location of lightning strokes for the purpose of public safety and weather forecasting and warning operations. Archived LDS datasets also provide support to electric utility companies to identify lightning events associated with electric power grid faults and power outages, reduce frequency and duration of power outages, and make improvements to transmission line segments susceptible to lightning damage. More importantly, flash rate and density measurements are necessary for the inference of cloud thermodynamical and microphysical processes that favor severe thunderstorm hazard phenomena including hail, tornadoes, and damaging winds (downbursts).
A New Lightning Climatology for Cape Canaveral Air Force Station and NASA Kennedy Space Center
2017
The 45th Weather Squadron (45 WS) is the U.S. Air Force unit that provides weather support to America’s space program at Cape Canaveral Air Force Station (CCAFS) and National Aeronautics and Space Administration (NASA) Kennedy Space Center (KSC). The weather requirements of the space program are very stringent (Harms et al., 1999). In addition, the weather in east central Florida is very complex. This is especially true of summer thunderstorms and associated hazards. Central Florida is ‘Lightning Alley’, the area of highest lightning activity in the U.S. (Holle et al., 2016). The 45 WS uses a dense network of various weather sensors to meet the operational requirements in this environment (Roeder et al., 2003). A new lightning climatology was developed for CCAFS/KSC. The purpose is to update the previous lightning climatology to improve lightning risk assessment. In particular, a method was developed to infer a new parameter, the density of lightning ground contact points, which is ...
2012 International Conference on Lightning Protection (ICLP), 2012
This is an event driven, 100 MS/s sampling system, which includes six synchronized high-speed video cameras installed atop each of the three towers (two per tower) and one remote high-speed video camera installed about five kilometers southwest of LC39B (temporarily installed in the firing room I of the Launch Control Center (LCe) pending final installation atop the Vehicle Assembly Building (VAB». Current sensors installed at ground level on each of the nine downconductors of the LPS; four dH/dt, 3-axis measurement stations; and five dE/dt stations composed of two antennas each. The electromagnetic sensors are all installed at ground level with elevations The LC39B LPS and its instrumentation are described in detail in [I] and [2], respectively. The LPS can be seen as two independent, but synchronized, data acquisition systems, Lightning and Weather [3] both running 24/7. In general, the LPS consists of a catenary wire system (at about 181 meters above ground level) with nine downconductors connected to ground, supported by three insulators installed atop three towers in a triangular configuration. Field sensors' signals are digitized and transmitted, via fiber optics, to centralized transient recorders located in the Pad Termination Connection Room (PTCR). All the LPS instrumentation, including the digitizers, transient recorders, and computers, are battery backed up.
NASA, at the John F. Kennedy Space Center (KSC), developed and operates a unique high-precision lightning location system to provide lightning-related weather warnings. These warnings are used to stop lightning- sensitive operations such as space vehicle launches and ground operations where equipment and personnel are at risk. The data is provided to the Range Weather Operations (45th Weather Squadron, U.S. Air Force) where it is used with other meteorological data to issue weather advisories and warnings for Cape Canaveral Air Station and KSC operations. This system, called Lightning Detection and Ranging (LDAR), provides users with a graphical display in three dimensions of 66 megahertz radio frequency events generated by lightning processes. The locations of these events provide a sound basis for the prediction of lightning hazards. This document provides the basis for the design approach and data analysis for a system of radio frequency receivers to provide azimuth and elevation...
Journal of Geophysical Research, 2011
1] We evaluated performance characteristics of the U.S. National Lightning Detection Network (NLDN) using rocket-triggered lightning data acquired in 2004-2009 at Camp Blanding, Florida. A total of 37 negative flashes that contained leader/return stroke sequences (a total of 139) were triggered during these years. For all the return strokes, locations of channel terminations on the ground were known exactly, and for 122 of them currents were measured directly using noninductive shunts. The NLDN recorded 105 Camp Blanding strokes in 34 flashes. The resultant flash and stroke detection efficiencies were 92% and 76%, respectively. The median absolute location error was 308 m. The median NLDN-estimated peak current error was −6.1%, while the median absolute value of current estimation error was 13%. Strokes in "classical" triggered flashes are similar to regular subsequent strokes (following previously formed channels) in natural lightning, and hence the results presented here are applicable only to regular negative subsequent strokes in natural lightning. The flash detection efficiency reported here is expected to be an underestimate of the true value for natural negative lightning flashes, since first strokes typically have larger peak currents than subsequent ones.