Potter T.D., Colman B.R. (co-chief editors). The handbook of weather, climate, and water: dynamics, climate physical meteorology, weather systems, and measurements
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Recent litigation
8
resulting from a six-death crash of a private plane attempting a
nighttime VFR landing at a Florida airport hinged on whether the sky condition
‘‘measured’’ by a human observer was ‘‘measured 600 foot broken clouds’’ (cover-
ing 6=10ths of the sky with opaque clouds), technically IFR conditions, or whether
these clouds had moved away, allowing the field to become VFR.
The case was complicated by a number of conflicting eyewitness postaccident
statements regarding the sky condition at the airport at the time of the accident. Two
testifying forensic meteorologists offered very differing opinions in testimony before
the court during trial. Statements by two IFR-rated pilots who ‘‘lost sight of the
airport on arrival’’ and ‘‘encountered an unreported cloud layer on departure’’ near
the accident time were significant in the retrospective weather reconstruction.
Conflicting Views
Another aviation litigation case in which the testimony of two eminently qualified
forensic meteorologists offered dramatically different opinions on the atmospheric
conditions involved a tragic in-flight breakup of a twin-e ngine aircraft over Anthony,
Kansas
9
(Haggard, 1983).
Far removed from any direct measurements, the question was whether:
1. The plane was in level flight between cloud layers (perhaps in light snow) with
no wind shear, no turbulence, and no icing when both engines and various
control surfaces broke off the aircraft; or
2. The plane flew through a strong wind shear zone with a dramatic weather
change into freezing rain and severe turbulence, resulting in an upset and
overstresses, which led to the in-flight breakup.
Both experts utilized the same archived weather measurements. One relied upon a
computer analysis that indicated strong rotation but minimal shear in the wind field
at flight altitude. The other relied on a ‘‘hand analysis’’ (not dependent on computer-
programmed analysis procedures) that showed less rotation but a very strong shear
zone in the wind field.
Changing Environment
The validity of weather measurem ents may be degraded by changing environmental
circumstances. A recent tragic example was the failure of the LLWAS at Charlotte,
North Carolina, to detect and warn of the small but stro ng microburst associated
with the crash of USAir Flight 1016 on the evening of July 2, 1994 (Fujita and
Haggard, 1995; Haggard and Fujita, 1994).
Installed in 1981, the six sensors of the system were mounted on poles at heights
ranging from 20 to 68 ft on and near the Charlotte, North Carolina, Douglas Inter-
national Airport in rolling terrain largely covered by early-growth pine. Between
1981 and 1994 many of the pines grew to heights equal to or greate r than the height s
836 DEMANDS OF FORENSIC METEOROLOGY
of the wind sensors (see Fig. 3), degrading their wind measurements (and their
ability to sense and warn of significant wind shear).
4 WITNESS CREDIBILITY
In these (and other) examples of weather-related litigation, the court ( judge and=or
jury) must consider the ‘‘testimony and demeanor’’ of each witness to determine
their credibility. Credibility is enhanced by demonstrated reliance on valid meteor-
ological measurements and sound scientific procedu res.
The adversarial system of justice in the United States should not impact on the
expert witness. The parties and the attorneys are adversaries and advocates. The
expert witnesses should be objective scientists utilizing valid measurements and
objective techniques. Procedures for bringing scientific facts forth in the cour troom
are very different than in a scientific symposium (Bradley, 1989).
Figure 3 LLWAS anemometers at Charlotte, North Carolina, in 1994. Upper photo is of
northwest sensor; lower photo is of southeast sensor; each shows sensors in relation to forest
growth. See ftp site for color image.
4 WITNESS CREDIBILITY 837
Decisions by various courts suggest (Haggard, 1989) that it is essential that the
testifying expert:
Reduce his or her opinion to the simples t terms possible.
State (and visually illustrate) the opinion(s) clearly and concisely.
Demonstrate (visually and orally) the factua l basis for the opinion.
Produce authenticated copies of all weather measurements relied upon.
Demonstrate reliance upon the most accurately observed and adequately
quality controlled meteorol ogical measurements available.
Ensure the bridge from demon strable facts to the stated opinion is as short and
solid as possible (i.e., ‘‘let the data speak for themselves’’).
The meteorological expert must avoid any appearance of advocacy (Saks, 1987)
and adhere to the scientific analysis of the highest quality validated meteorological
measurements available (Haggard, 1985).
CASE CITATIONS
1. Kavairlook v. Ryan Air Service, Superior Court for the State of Alaska (Nome-Koyuk
12=10=94).
2. Kaufman v. Beech Aircraft, Superior Court of the State of California for the County of Los
Angeles (Flagstaff, AZ, 12=20=91).
3. M=V Summit Venture, United States District Court Middle District of Florida Tampa Division
(Sunshine Skyway Bridge, Tampa, FL, 5=9=80).
4. Kathleen Connors et al. v. USA, United States District Court for the Northern District of
Texas, Ft. Worth Division (DL 191, DFW, TX, 8=2=85).
5. American Enka v. Southern Railroad, United States District Court for the North Carolina
District of Asheville, NC (Enka, NC, 11=7=7).
6. Leslie et al. v. American Airlines et al., United States District Court for the District of Puerto
Rico (Mayaguez, PR 6=7=92).
7. John Overby v. USA, U.S. District Court for the District of Alaska (N-S runway at Anchorage
International Airport).
8. McNair v. USA, United States District Court Nor thern District of Florida Gainesville
Division (Gainesville, FL, 6=7=95).
9. Buzzard v. Piper, District Court for Oklahoma County, Oklahoma City, OK (Anthony, KS,
2=11=77).
REFERENCES
Bradley, M. D. (1983). The Scientific and Engineer in Court, Am. Geophys. Union Water
Resources Monograph 8, Washington, DC.
Falconer, P. D., and W. H. Haggard (1990): Forensic Meteorology, Forensic Sciences, New York,
Matthew Bender, Chapter 35.
838
DEMANDS OF FORENSIC METEOROLOGY
Fujita, T. T. (1986). DFW Microburst on August 2, 1985, SMRP Res. Paper No. 217; Chicago,
University of Chicago Press.
Fujita, T. T., W. H. Haggard, and W. A. Bohan (1992). Puerto Rico’s Weather of June 7, 1992
Related to the Crash of Executive Air Flight 5456 at Mayaguez, Puerto Rico, submission by
Construcciones Aeronauticus, SA [CASA] to the National Transportation Safety Board,
Washington, DC, November.
Fujita, T. T., and W. H. Haggard (1995). The Microburst at Charlotte, North Carolina in
Relation to the Crash of USAir 1016 on July 2, 1994, A Report to The Air Line Pilots
Association ALPA, January.
Haggard, W. H. (1980a). Radar Imagery for Past Analysis of Mountain Valley Flash Floods,
Proc. 2nd Conf. on Flash Floods, Atlanta, GA, Boston, American Meteorological Society.
Haggard, W. H. (1980b). What’s in a Wind Study? Proc. 2nd Joint Conf. on Industrial
Meteorology, New Orleans, LA, Boston, American Meteorological Society.
Haggard, W. H. (1980c). Some Micro-Economic Aspect of Applied Climatology, Proc.
Conf. on Climatic Aspects and Social Responses, Milwaukee, WIs, Boston, American
Meteorological Society.
Haggard, W. H. (1983). Weather after the Event, Proc. 9th Conf. on Aerospace and
Aeronautical Meteorology, Omaha, NE, Boston, American Meteorological Society.
Haggard, W. H. (1985). Meteorologists as Expert Witnesses, Proc. 15th Conf. of Broadcast
Meteorology, Honolulu, HI, Boston, American Meteorological Society.
Haggard, W. H. (1989). Weather Testimony in Litigation, Proc. 3rd Int. Conf. on the Aviation
Weather System, Anaheim, CA, Boston, American Meteorological Society.
Haggard, W. H., and T. T. Fujita (1994). The LLWAS at Charlotte, North Carolina in Relation to
the Microburst of July 2, 1994, A Report to The Air Line Pilots Association ALPA,
September.
Haggard, W. H., and S. W. Smutz (1994). Forensic Meteorology; Proc of 7th Aviation
Law=Insurance Symposium, Daytona Beach, Fl, Embry Riddle Aeronautical University.
Saks, M. J. (1987). MIT Tech. Rev., Aug=Sept.
REFERENCES 839
CHAPTER 43
SURFACE LAYER IN SITU OR
SHORT-PATH MEASUREMENTS FOR
ELECTRIC UTILITY OPERATIONS
ROBERT N. SWANSON
1 INTRODUCTION
Electric utility operations, as interpreted in the following discussion, involves day-
to-day operations, engineering requirements for planning, designing, and operating a
system, applied research, as well as environmental concerns and=or requirements.
Several aspects of measurements are discussed elsewhere in this Handbook and will
not be repeated in this chapter. Meteorological data sets, collected as part of any
operational or research program, require detailed knowledge of sensor and data
retrieval system charact eristics and employ proper quality assurance=quality control
(QA=QC) procedures. It also involves sensor siting guidelines to assure maximum
information is obtained from the measurement program. Since utilities measurement
needs may extend throughout and above Earth’s boundary layer, their programs are
not necessarily restricted to the use of in situ or short-path sensors.
2 RECENT HISTORY OF METEOROLOGICAL REQUIR EMENTS BY
ELECTRIC UTILITIES
Until the early 1950s, meteorological information used by electric utilities, if any,
were those collected and transmitted by the federal government. Simple adjustments
were sometimes made to these data to compensate for local extreme conditions for
purposes of power generation or system line loading. Occa sionally systems were
Handbook of Weather, Climate, and Water: Dynamics, Climate, Physical Meteorology, Weather Systems,
and Measurements, Edited by Thomas D. Potter and Bradley R. Colman.
ISBN 0-471-21490-6 # 2003 John Wiley & Sons, Inc.
841
operated at above rated levels, and the situations were not considered serious until
they impacted operations in some manner. Reliability of power delivered to the
customer was not always an overriding concern with power outages generally tol-
erated and=or expected by the user. In the 1950s, when nuclear power plants were
first being built on a commercial basis, there was a developing interest in the trans-
port and dispersion of potential releases of nuclear material. This interest or concern
resulted in the development of meteorological monitoring programs at both nuclear
and conventional power plants. These monitoring programs were developed to
provide inputs to existing dispersion models. Early monitoring programs were
quite simplistic in that they frequently collected very limited information of ques-
tionable quality. For example, at Humbolt Bay Nuclear Plant in northern Califor nia,
wind meas urements at this nuclear plant consisted of a single aerovane mounted on
top of a tower near the plant. Calibration and=or maintenance of this sensor was not
well established and possibly was never done.
As time passed, new and more complex dispersion and transport models were
developed that, in turn, required additional met eorological information. Because of
this requirement, as well as because of an increased concern by the public over
safety, more sophisticated and better designed monitoring programs were developed.
After the belief that nuclear power would be both inexpensive and plentiful was
challenged, there was an increased interest in alternate energy development and in
energy conservation. Both of these programs had additional meteorological require-
ments beyond those provided by the National Weather Service (NWS) with the
largest uncertainties associated with planned alternate energy projects. This situation
was readily apparent because NWS sites were generally located at airports with a
lesser number of observation sites in urban areas. Neither of these sites would be
representative of wind energy farms that were being evaluated. Until the mid-1970s
wind energy and=or photovoltaic power sources were given little or no attention by
electric utilities. This lack of interest was a result of many things, including cost,
equipment availability, equipment reliability, and, of course, the already existing
power-generating network.
In general each of the alter nate energy programs, including wind, photovoltaic,
hydroelectric, or geothermal power, have their own particular meteorological
monitoring requirements. Also increasing concerns over public health issues and
conservation of natural resources have created many changes in meteorological
monitoring needs after the early 1950s.
3 MEASUREMENT REQUIREMENTS
Meteorological measurement requirements for electric utility operations can
normally be met with existing off-the-shelf sensors and digital recording systems.
Siting of these sensors to best address specific concerns or needs of a project is likely
a more difficult task than is proper sensor selection. It is important to consider that
measurements collected for one program may well be integrated into another, pos-
sibly unrelated, program. Therefore consideration should be given to this possibility
842 SURFACE LAYER IN SITU OR SHORT-PATH MEASUREMENTS
when selecting and=or siting sensors and in data processing and archiving incoming
data. This consideration should in no way detract from the original goal of collecting
the best possible data set for the specific project to be evaluated. Additional infor-
mation generated in data processing and archiving should always be considered
since it represents only a minimal increase on the overall level of effort and may
well provide valuable information to be used with another project.
Measurement programs should be designed to meet as many of the objectives as
possible within budget constraints. These designs can become very difficult at times.
For example, when monitoring for wind energy or photovoltaic farms in complex
terrain, consideration must be given to many factors including terrain elevation and
contours, cloud cover changes, temperature differences, and winds. If the site(s)
locations are near large water masses, additional issues may exist. Frequently discus-
sions with long-time residents in the area will provide valuable insight into specific
conditions that would otherwise take an extended monitoring period to determine.
4 MEASUREMENT GUIDELINES
As mentioned above, most measurement program needs for electric utility operations
can be easily satisfied with existing equipment. However, needs arise to examine the
atmosphere above the lower boundary layer. When these needs exist in situ and=or
short-path sensor measurements will have to be augmented with additional sensor s
such as long-path remote sensors or acoustic sounders. One example of such a
program is cloud seeding for snow pack enhancement in an atte mpt to increase
hydroelectric power. For this effort the atmospheric structure must be well defined
through a very deep layer. Siting off the non-in-situ sensors for use in special
programs is project specific and therefore cannot b e given detailed guidelines
except to follow rigid QA=QC policies. In designing a measurement program, the
primary consideration is to determine the overall object ive(s) of the project and then
design a total system that will best address all concerns within the b udgetary
constraints that are levied on the effort.
Effective measurement programs require adhering to good QA=QC guidelines.
Examples of such guidelines are ANSI=ANS-3.11 (ANS, 2000b) and EPA (1989).
Both of these documents provide guidelines that will, if followed, assure a reason-
ably successful monitoring program, but, as with most efforts, deviations from the
guidelines may have to occur. One typical deviation is in actual sensor siting where it
is frequently impossi ble to meet all guidelines on distances of the sensor from
obstructions. In such cases common sense must prevail and the sensors should be
located where the smallest negative impacts will be found.
5 DATA ACQUISITION
Digital data acquisition systems can provide totally adequate data collection, storage,
and transmi ssion packages because of their speed, accuracy, and overall reliabil ity.
5 DATA ACQUISITION 843
Backup devices, such as strip-chart recorders, can be included in a monitoring
program, but they add a significant level of effort and cost to the program while
providing little redeeming information not already available with properly
programmed digital systems. All maintenance and calibration efforts must be
done using technically competent personnel. Data retrieval, processing, checking,
editing and archiving should also be patterned after an accepted guideline, such as
ANSI=ANS-3.11, in a manner similar to programs for field measurements. Statistical
procedures should be established, using incoming data, to assist in assessing data
quality and operating condition of measurem ent devices. These statistical programs
should be established at or near the beginning of a measurement program to capture
diurnal and seasonal variations. It is critical that any deterioration of sensor perform-
ance be detected and corrected as soon as possible to maintain a valid collection
efficiency of 90% or better from all sensors on an annual basis. The definition of
‘‘valid’’ data capture must also be quantified to prevent all incoming values from
becoming valid readi ngs regardless of quality.
6 EXAMPLE OF METEOROLOGICAL REQUIREMENTS BY AN
ELECTRIC UTILITY
A large electric utility in western United States, in the early 1990s, had a complete
weather forecast office in addition to a significant sized group of personnel in a
meteorological projects section. Many requests for infor mation and=or studies done
within the weather forecast office will not be discussed below as the following tasks
represent only the major items requested of the projects section. This list is not
intended to be all inclusive but is given only to illustrate the types of programs
with which meteorology may become involved. Also it is not intended to reflect the
meteorological research needs of other electric utilities since it is unique in size,
type, and expanse of service territory and generation mix. Major study efforts by the
projects section included:
1. Electric load management and load research. These are primarily regulatory
issues because electric rates are determined by typical meteorological condi-
tions within specific geographical areas. Routine measurements of tem perature
and humidity at about 25 locations throughout the utilities service area
satisfied the requirements for this project.
2. Transmission line loadi ng (dynamic thermal rating). This program consisted
of wind and associated temperat ure measurements along major transmission
lines. Critical conditions that may cause transmission line ratings to be
exceeded occur with very low ventilation rates and high ambient temperatures.
Wind speeds of interest, perpendicular to the power line, are in the 0.25 to
2.0 m=s range so the wind sensors must have a low starting threshold.
Temperature measurements within about 1.0
of tr ue are quite sufficient for
this type of study. Since this program was implemented in the early 1990s,
844 SURFACE LAYER IN SITU OR SHORT-PATH MEASUREMENTS
new and probably better measurement systems for dynamic thermal rating
have entered the market.
3. Alternate energy system feasibility. Studies in this program include those for
photovoltaic, wind, and geothermal development. Photovoltaic and wind
energy farm potentials are very site specific. Photovoltaic farm feasibility is
dependent on distribution of cloud cover, evaporative cooling, atmospheric
turbidity, and ambient temperature. Wind power is dependent on wind flow
distribution in time and space, quality of wind such as wind shear and
turbulence, time of day, and time of year. Geothermal power concerns are
primarily transport and diffusion of released pollutants and of cooling tower
siting and their operating efficiency. Each of these alternate energy programs
had its own measurement requirements and each monitoring effort was
unique. Wind tunnel modeling, covering a several square kilometer range,
was completed for a potential wind energy farm site.
4. Power line and transformer contamination. This study centered around
transmission lines, transformers, insulators, and substations where contamin-
ant buildup can create equipment malfunction. Costs of washing these pieces
of equipment are very high and a realistic washing schedule was desired.
Conventional sensors for measuring winds, humidity, net radiation, and
surface temperatures of transformers were used.
5. Environmental impacts from released pollutants. These studies were primarily
done for planned and=or operational fossil fuel, nuclear, geothermal, and
hydroelectric power plants. General concepts, techniques, and instr umentation
needed for estimating pollutant transport and dispersion are discussed else-
where in this Handbook and so will not be discussed here. However, most of
the power plants are located in complex terrain where released pollutant
transport and dispersion is modified by the plume’s flow around terrain
obstacles. Realistic estimates of environmental impacts from released material
frequently required additional measurement sites along the plume’s trajectory.
Three-dimensional wind tunnel modeling of several of the geothermal sites
were completed as part of a transport and dispersion study.
6. Wind, ice, and snow loading on transmission towers and power lines. Much of
the information used in this study was derived from climatological data with a
limited number of measurement sites in the field. Since this program was site
or area specific, the measurement program was tailored for each area of
concern. One major problem area in the implementation of this study was to
employ sensors that would provide accurate data at times when icing or
snowing conditions occurred. This problem was not adequately solved, but
new systems such as use of line tension monitoring sensors, may be of
considerable assistance in this type of study.
7. Cloud seeding to increase snow pack for hydroelectric operations. This effort
involves three-dimensional wind speeds and directions, temperatures, and
humidities from the seeding area to heights above clouds having seedable
moisture. In situ measurements of wind and precipitation used in this study
6 EXAMPLE OF METEOROLOGICAL REQUIREMENTS BY AN ELECTRIC UTILITY 845