U.S. agency and agency-sponsored programs for lightning detection are listed. Research and development in the area of lightning sensors is described

Hovey, Russell L.

English

NASA Technical Reports Server

LIGHTNING DETECTION 
AND LOCATING SYSTEMS 
Russell L. Hovey 
Office of the Federal Coordinator 
for Meteorology (DOCIN WS) 
Introduction 
In September 1983, the Office of Inspector General (OIG), Office of Audits 
(OA), Denver Regional Office (DRO), and the United States Department of Com- 
merce (DOC), published a management audit report entitled, "Thunderstorm Killers 
- Flash Floods and Lightning, Need to Improve Severe Weather Forecasting." The 
purpose of the review was stated to evaluate National Weather Service ( S W S )  se- 
vere weather forecasting and to determine possible improvenlents in forecasting life- 
threatening severe weather, especially flash floods and lightning. The report briefly 
reviewed the historical development of severe storm forecasting, reviews loss-of-life 
statistics due to severe weather, and concludes that lightning has killed more people 
from 1940 through 1981 than tornadoes and hurricanes combined. Specific conclu- 
sions and recommendations were provided which are directed toward improving the 
national capability in providing public warnings of flash flood and lightning. 
Federal agencies have pointed out that there are several coordinating mecha- 
nisms at  work regarding the overall lightning issue. They also agree that improved 
coordination among agencies operating lightning detection systems might be mutu- 
ally advantageous. As a result of this stimulus and general agreement among con- 
cerned agencies, there was a positive response to  a request from DOC members of the 
Interdepartmental Committee for Meteorological Services and Supporting Research 
(ICMSSR) for preparation of a report on present and planned lightning detection 
systems by the Office of the Federal Coordinator for ?vIeteorology (OFChI). 
A report is being prepared under the guidance of the OFCM for containing 
information outlining the present and ~ l a n n e d  lightning detection capability in all 
agencies and discusses opportunities for data sharing and cooperation. 
Agency and Other Programs 
Interest in lightning and lightning detection is evident in the programs of the 
governmental agencies, academia, industry (such as power companies), and the gen- 
eral public as served by T V  stations. Each has particular interests and objectives. 
The following is a brief summary of these interests and programs of government 
agencies. 
https://ntrs.nasa.gov/search.jsp?R=19880015728 2020-03-20T06:46:36+00:00Z
Summary of Agencv Proprams: 
The Western United States and Alaska are essentially covered by an op- 
erational lightning detection network operated and maintained by the De- 
partment of Interior, Bureau of Land Management (BLM) . "Real-time" 
data are provided to other agencies. 
The Eastern United States has a research network operated by the State 
University of New York (SUNY) a t  Albany, New York. It is an expanding 
network funded by the National Science Foundation (NSF), by SUNY and 
partially by private industry and other government agencies. Data are 
made available to government and industry by special arrangement with 
SUNY. 
The Department of Defense, U. S. Navy (DoD/USN), either has or is 
planning significant activities covering the Eastern and Central U. S. These 
facilities are operated at  present as local use facilities and are not in a 
network configuration. 
Other lightning detection facilities exist in the East Central U. S. which 
are not part of network configurations. Incorporating these facilities into 
existing or planned networks will require communications (ground or satel- 
lite) and data processors. 
Detection facilities are of two basically differing techniques: time of arrival 
and magnetic field direction finders (DF), and controversy remains con- 
cerning the relative capability of each. Thus the facilities are not compat- 
ible. but the data from each can be accommodated in a data distribution 
system which would accept processed data from the different detection 
networks. 
The SUNY network (currently characterized as an R&D network), if in- 
cluded as a part of a national network, would require some organiza- 
tional and funding arrangements to accommodate the commitments al- 
ready made by SUNY and to assure availability of the system as part of 
an operational network. 
Currently, there are no federal standards within which the existing sys- 
tems must operate. Use of differing systems raises questions of relative 
accuracies, false alarm rate, etc. Procedural instructions of standards will 
most certainly be required in a network configuration. 
There are no well-established arrangements for archiving operational data 
from existing or planned networks. The Department of Interior (BLM) 
has initiated an arrangement and agreement with the other agencies (De- 
partment of Agriculture, Forest Service, and possibly others) at  its facility 
in Boise, Idaho. 
In some cases, funding of lightning detection research or operations by 
agencies is part of larger funded programs and are not identifiable as 
uniquely funded programs. 
Sensor System Descriptions 
Several lightning detection sensor designs have been developed in recent years 
which are the basis for lightning (sferics) detection systems. The three most preva- 
lent of these design approaches are: 
1. The magnetic direction finding equipment developed by Krider and now 
manufactured by Lightning Location and Protection, Inc. (LLP),  which 
utilizes the angle-of-arrival approach; 
2. A time-of-arrival (TOA) system developed by Bent and manufactured by 
Atlantic Scientific Corporation; 
3. A satellite-borne lightning imager consisting of a fast lens telescope. a nar- 
row band interference filter, and a focal plane photon detector developed 
by NASA. 
Although systems for the detection and tracking of lightning bolts have been 
around since the days of Ben Franklin, modern techniques use one of these basic 
sensor designs. 
The physical mechanisms upon which the generation of lightning is based are 
not universally agreed upon; however, it is generally accepted that lightning is 
a thermodynamic process within a cloud resulting in a big spark generator. This 
process sets the stage for cloud-to-ground, cloud-to-cloud, and intracloud discharges. 
The ground-based lightning detection systems now being implemented are de- 
signed for the detection of cloud-to-ground discharges. Except for the Ryan Storm 
Scope, these systems take pains to filter out intra-/intercloud discharges between 
storm cells. 
Cloud-to-ground discharges occur when the cloud potential reaches a level near 
breakdown and a leader or spark is generated between the cloud and earth. The 
leader creates an ionized trail which, when it reaches striking distance to Earth, 
results in the main stroke of approximately 2 0 0 K  amperes from earth to the cloud 
following the ionized trail left by the leader. Four or five return strokes approxi- 
mately 10 microseconds in duration occur for each leader within a few milliseconds. 
These strokes generate an Electromagnetic Pulse (EMP) which radiates radio fre- 
quency (RF) energy or noise which is the signal detected by the sensors. Most of 
the energy is in the Very Low Frequency (VLF) 1 KHz band and is distributed a t  
decreasing amplitudes up through the Ultra High Frequency (UHF) 10 GHz band. 
A similar mechanism occurs for intra-lintercloud discharges between cells within 
a cloud and for cloud-to-cloud discharges. The EMP intensities of these discharges 
are a fraction of the cloud-to-ground discharge. Even so, the electromagnetic fields 
generated by the discharges can induce potentials in power and signal lines which 
have disastrous effects. 
The magnetic direction finding equipment senses the electromagnetic fields of 
the lightning using two orthogonal magnetic loop antennas and a flat plate electric 
field antenna. A wide bandwidth (1 MHz) receiver is used to  preserve the shape of 
the pulse. The system is designed to  respond only to the waveshape characteristic 
of the cloud-to-ground flashes. This equipment outputs the angle with respect to  
north of the observed EMP. The system manufactured by LLP consists of two or 
more gated, wideband magnetic DF stations that are separated by tens-to-hundreds 
of kilometers and transmit lightning direction and signal amplitude data to  a central 
position analyzing (PA) computer. When the PA receives two or more simultaneous 
inputs from the remote DF stations, it computes the location of the lightning source 
by either triangulation or the DF angle vectors (Figure 1). 
The TOA equipment consists basically of two receivers, one to  detect the light- 
ning stroke and the other to detect the highly accurate LORAN timing source. 
The TOA equipment uses a VHF wideband receiver to  detect the lightning and 
the LORAN C 100 KHz receives timing pulses for synchronization. The output of 
this equipment is the arrival time of a lightning pulse with respect to the LORAN 
C synchronization pulse. The system locates the source of the EMP by plotting 
the arrival time of the pulse from two or more receiving stations. As a result, the 
receiving equipment is quite simple. 
Atlantic Scientific Corporation developed a system (LPATS) which uses three 
or more (usually four) TOA sensor stations all synchronized to the same LORAN C 
timing source. These stations are connected via dedicated communications circuits 
to  a central analyzer facility which measures the difference in the times of arrival 
from the geographical dispersed sensors and determines the location of the lightning 
using hyperbola triangulation (Figure 2) .  Tests using TOA systems were conducted 
by the Air Force Wright Aeronautical Laboratories (AFWAL) in 1979, 1980, and 
198 1. 
The Ryan Storm Scope is an  airborne, or may be ground-based, lightning 
detection system which uses the magnetic direction finding crossed loop and sense 
antenna sensor to detect the range and azimuth of lightning discharges. Azimuth 
is determined from the ratio of the two crossed loop antenna inputs. Range is 
determined by measuring the field strength of the lightning discharge with respect 
to a constant. The constant is derived from an assumption that the field strength 
is relatively constant from discharge to discharge and inversely proportional to the 
square of the range. A CRT readout with memory provides a plan position display 
of the lightning strikes. There are about 7,000 storm scopes installed and in use as 
an in-flight weather avoidance and lightning detection system. 
The AFWAL tested the system in the summer of 1981. The results of the tests 
are contained in AFSC Report AFWAL-TR-83-3083. Basically, they concluded that 
the storm scope shows reasonable accuracy in azimuth and fairly large inaccuracies 
(+ or - 25 miles) in range. 
The Ryan Storm Scope Company has been acquired by the 3M Company. The 
3M Company has incorporated several improvements in the Ryan Storm Scope and 
now markets it as a 3M product. 
NASA has developed a lightning imaging system for installation on a GOES- 
type satellite which will detect and locate lightning over large areas of the earth. The 
system has not been implemented and is expected to require additional refinement 
because of the strong background noise produced by sunlight reflection from tops 
of clouds. 
I~rlplementation of any of these systems should consider: 
1. Overall agency requirements 
2. Communications costs. A high-quality dedicated duplex telephone circuit 
costs about $12,000 per year for each PL4 
3. Detection and tracking of both intra- and intercloud lightning 



Lightning detection and locating systems

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