National Lightning Detection Network (NLDN) of Improved Performance from Combined Technology (IMPACT) Radio Frequency Antenna System

Summary:

The U.S. National Lightning Detection Network is a commercial lightning detection network operated by Global Atmospherics, Inc. (GAI), (formerly Geomet Data Services), since 1991. A network of about 105 antenna stations are connected to a central processor that records the time, polarity, signal strength, and number of strokes of each cloud-to-ground lightning flash detected over the United States. A combination of time-of- arrival and direction finding technology is used to locate the flash. Depending on the location within the network, GAI claims a location average accuracy of 500 meters, with a detection probability between 80-90 percent, varying slightly by region. This document contains information about Improved Performance from Combined Technology (IMPACT) Antennas. IMPACT combines direction finding and time-of-arrival information which determines location and time of a cloud-to-ground lightning flash. The IMPACT antenna system receives radio frequencies. Distribution of this data set is restricted to Earth Observing System (EOS) affiliated investigators.

Table of Contents:

1. Sensor/Instrument Overview:

Sensor/Instrument Long Name, Sensor/Instrument Acronym:

Improved Performance from Combined Technology (IMPACT) Antenna System

Sensor/Instrument Introduction:

The GAI, (formerly Lightning Location and Protection, Inc.), IMPACT Lightning Locating System estimates both the location and time of occurence of the return stroke. Each sensor provides information on azimuth and the time it took the signal to propagate from its origin to the station (absolute arrival time minus the estimated time of occurrence). The azimuth establishes a vector from the sensor to the stroke, while the propagation time establishes distance (range), thus defining a circular locus of possible locations around the sensor. Location and time are determined by iteratively adjusting initial estimates of these parameters so that differences between observed and calculated azimuths and propagation times are minimized. Location accuracy has been estimated as 500 meters or better in areas surrounded by sensors using the IMPACT location algorithm.

Sensor/Instrument Mission Objectives:

IMPACT Lightning Locating Systems are being used to determine the location, movement, and intensity of thunderstorms; to facilitate early detection of lightning-caused fires; to determine whether electric power outages are lightning-caused; to warn of impending lightning hazards; and for a number of other applications and basic research.

Key Variables:

Cloud-to-ground lightning flash
Cloud-to-ground lightning stroke

Scanning or Data Collection Concept/Principles of Operation:

Location and time are determined by iteratively adjusting initial estimates of the parameters so that differences between observed and calculated azimuths and propagation times are minimized. When only two stations detect a flash, there is redundant information for an optimized estimate of location. In that case there are four measured parameters (two azimuths and two arrival times), while only three parameters are estimated (latitude, longitude, and time). Although GAI systems detect and analyze individual return strokes from each flash, they group all strokes that belong to the same flash and provide only one data record per flash. This record contains time, location, and peak signal amplitude of only the first return stroke, but provides multiplicity or number of strokes that made up the flash.

2. Sensor/Instrument Layout, Design, and Measurement Geometry:

List of Sensors:

Improved Performance from Combined Technology (IMPACT) Antenna System

Sensor Description:

The IMPACT location algorithm is a general approach to allow arbitrary combinations of timing-based and angle-based sensors. The only constraint for a location solution is that there are more independent observations of angle and/or time than there are variables to estimate (latitude, longitude, and stroke time). The NLDN is designed to have an average of 6-8 sensors contributing to the location of a stroke.

3. Manufacturer of Sensor/Instrument:

The IMPACT lightning detection equipment is manufactured by Global Atmospherics, Inc. of Tucson, Arizona. GAI operates the National Lightning Detection Network for the continental United States, and sells the data to a variety of users.

4. Calibration:

Specifications:

Tolerance:

Depending on the location within the network, GAI claims a location average accuracy of 500 meters, with a detection probability between 80-90 percent, varying slightly by region. The accuracy of lightning locations depends on:

  • Variability in detection efficiency
  • Variability in peak current estimates
  • Determination of flash multiplicity
     

    • Frequency of Calibration:

    This information is not available at this time.
     

    Other Calibration Information:

    At this time, direct calibration of peak current for positive cloud-to-ground strokes has not been achieved (Cummins, K.L., et al., 1995).
     

    5. References:

    Cummins, K.L., et al., 1995: NLDN'95: A Combined TOA/MDF Technology Upgrade of the U.S. National Lightning Detection Network. Intl. Aerospace & Ground Conference on Lightning and Static Electricity, Williamsburg, VA, USA, Sept. 26-28, 1995.

    Cummins, K.L., R.O. Burnett, W.L. Hiscox, and A.E. Pifer, 1993: Line Reliability and Fault Analysis Using the National Lightning Detection Network. Preprints, Precise Measurements in Power Conference, Arlington, VA, Oct. 27-29, 1993.

    Cummins, K.L., W.L. Hiscox, A.E. Pifer, and M.W. Maier, 1992: Performance Analysis of the U.S. National Lightning Detection Network. Proceedings, 9th International Conference on Atmospheric Electricity. St. Petersburg, Russia. A.I. Voeilkov Main Geophysical Observatory, Karbysheva 7, 194018, St. Petersburg, Russia.

    Holle, R. H. and Lopez, R. E, 1993: Overview of Real-Time Lightning Detection Systems and their Meteorological Uses. NOAA Technical Memorandum ERL NSSL-102, National Severe Storm Laboratory, Norman, Oklahoma, October 1993.

    Maier, M. W., et al., 1983: Locating Cloud-To-Ground Lightning With Wideband Magnetic Direction Finders. Presented at 5th Symposium on Meteorological Observations and Instrumentation. Toronto, Ontario, Canada, April 11-15, 1983.

    Orville, R.E., 1994: Cloud-to-Ground Lightning Flash Characteristics in the Contiguous United States: 1989-1991. Journal of Geophys. Res., Vol. 5., 10833-10841.

    Reap, R.M., D.R. MacGorman, 1989: Cloud-to-Ground Lightning: Climatological Characteristics and Relationships to Model Fields, Radar Observations, and Severe Local Storms. Monthly Wea. Review, 117, 518-535.

    6. Glossary of Terms:

    Please see the GHRC Glossary for terms related to the GHRC and see EOSDIS Acronyms for a general listing of terms related to the Earth Observing System Project.

    7. List of Acronyms:

    Please see the GHRC Glossary for terms related to the GHRC and see EOSDIS Acronyms for a general listing of terms related to the Earth Observing System Project.

    GAI

    Global Atmospherics, Inc.

    IMPACT

    Improved Performance from Combined Technology

    NLDN

    National Lightning Detection Network

    URL

    Uniform Resource Locator

    8. Document Information:

    Document Revision Date:

    November 19, 1999
     
    Document Review Date:
     
    August 22, 1996

    Document ID:

    This information is not available at this time.

    Document Curator:

    GHRC User Services
    ghrc@eos.nasa.gov

    Document URL:

    http://ghrc.msfc.nasa.gov:5721/sensor_documents/NLDN_antenna.html