WMO Aeronautical Meteorology Scientific Conference 2017
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WMO Aeronautical Meteorology Scientific Conference 2017
6 - 10 November 2017
Centre International de Conférences - Météo-France - Toulouse - France
Session 1 – Science underpinning meteorological observations, forecasts, advisories and warnings
1.1 – En route phenomena
1.1.1 – Ice crystal icing, and airframe icing research
A High Ice Water Content (HIWC) Nowcasting Trial Exercise for
Enhanced Situational Awareness and Decision-Making Support
Julie Haggerty, NCAR
haggerty@ucar.edu
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co-author: Rodney Potts, BOM, rodney.potts@bom.gov.au
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speaker: Julie Haggerty
I. Introduction
Ingestion of large amounts of ice particles by jet engines, known as ice crystal icing (ICI),
appears to be the culprit in over 200 engine power-loss and damage events during the past
two decades. Typically these events have occurred at high altitudes near large convective
systems in tropical air masses (Mason et al., 2006). In recent years there have been
substantial international efforts by scientists, engineers, aviation regulators and airlines to
better understand the physical processes, solve critical engineering questions, develop new
certification standards and develop mitigation strategies for the aviation industry. One area of
research has been the investigation of nowcasting techniques to identify potential areas of high
ice water content (HIWC) and enable the provision of associated alerts to the aviation industry.
Such information is needed because new engine certification standards may largely mitigate
the risks associated with ICI for aircraft in the future but there is a large current fleet which
will be operating for many years. There is a recognised need for nowcasting guidance products
to support flight planning and management of the tactical response for these aircraft.
II. HIWC Nowcasting Methods
Efforts by several research teams are underway to develop techniques for detecting HIWC
based on principles gleaned from analysis of in-service ICI events and dedicated field
campaigns (Strapp et al., 2016). One such method is the Algorithm for Prediction of HIWC
Areas (ALPHA), developed by the US National Center for Atmospheric Research (NCAR) with
sponsorship from the United States Federal Aviation Administration (FAA). ALPHA is a
diagnostic tool that uses operationally available satellite data, numerical weather prediction
(NWP) model data, and ground based radar data (where available) as input. These input data
are blended via a set of fuzzy logic membership functions that maximize the strengths of each
data set (Haggerty et al., 2012). Figure 1 shows a simplified view of ALPHA processing. The
output from ALPHA is a 3-dimensional gridded field of the potential for HIWC conditions (Figure
2). HIWC Potential is a non-dimensional parameter that varies from 0 to 1; it can be thought
of as an uncalibrated probability of HIWC conditions.
A machine learning technique was applied to select the input variables, optimize the
membership functions, and determine weighting factors for blending the various data. In-situ
observations of ice water content (IWC) from research aircraft during a series of field
experiments were partitioned into a training data set and an independent verification data set
(Rugg et al., 2017). Figure 3 compares ALPHA HIWC Potential to IWC measurements from
three field experiments. Probability of detection is calculated assuming an IWC threshold of 0.5
g/m3 and an HIWC Potential threshold of 0.4 are indicators of HIWC conditions. ResultsWMO Aeronautical Meteorology Scientific Conference 2017
6 - 10 November 2017
Centre International de Conférences - Météo-France - Toulouse - France
indicate a high probability of detection, but with a significant false alarm rate. Work to further
improve the ALPHA algorithm is ongoing.
Figure 1: Overview of data input and processing in ALPHA. The output is a field, designated
“HIWC Interest” or “HIWC Potential”, giving the likelihood of HIWC conditions at a given
location. HIWC Potential
HIWC PotentialWMO Aeronautical Meteorology Scientific Conference 2017
6 - 10 November 2017
Centre International de Conférences - Météo-France - Toulouse - France
Figure 2: Example of ALPHA product in the north of Australia for FL330, 2245 UTC, 23 Jan
2014, with overlayed total water content (g/m3) measured by research aircraft.
False Alarm PoD-yes:
Rate: 20.6% 77.3%
Misses: 22.7%
PoD-no:
79.4%
Figure 3: HIWC Potential (Interest) from ALPHA vs. measured Ice Water Content for a
verification data set derived from three HIWC field experiments. Blue lines show IWC threshold
and HIWC Potential threshold that indicate HIWC conditions. Black line shows best fit to data
points. PoD is the probability of detection; false alarm rate = 1-PoDn.
III. Nowcasting Trial Exercise
A joint 2-year effort by the Australian Bureau of Meteorology (BOM) and NCAR, with support
from the FAA, provides an opportunity for evaluating ALPHA in an operational setting. This
project explores the means by which HIWC nowcasting tools could support airline operations
and promote development of an international capability for HIWC detection and forecasting.
Under this effort an experimental version of ALPHA will be implemented at the BOM over a
region across the north of Australia where there is frequent deep tropical mesoscale convection
and a high incidence of ICI events (Figure 4). The experimental ALPHA-BOM is currently being
configured to ingest data from HIMAWARI-8, the BOM Australian Community Climate and Earth
System Simulator (ACCESS) model (Puri et al, 2013), and BOM radar composite products
(Potts et al., 1999). Implementation and testing on a BOM server will begin soon.WMO Aeronautical Meteorology Scientific Conference 2017
6 - 10 November 2017
Centre International de Conférences - Météo-France - Toulouse - France
An initial trial of ALPHA is planned for the Australian summer monsoon period of January –
March 2018. Aviation industry stakeholders in the region, including BOM forecasters and
airlines, will be provided with digital and graphical products. Standardized feedback from users
of the experimental products will be provided to ALPHA developers. A second trial period is
planned for the monsoon season of 2019.
Figure 4: Geographic domain… (shown in orange). Area with BOM radar coverage is shown in
light gray.
IV. Expected Outcome and Future Plans
It is expected that findings from this exercise will provide insight on skill of ALPHA methods as
well as an enhanced understanding of user requirements for HIWC products. Additionally, the
exercise will provide aviation industry stakeholders in the region, including Bureau of
Meteorology forecasters and airlines, with experimental HIWC nowcasting products for
evaluation. NCAR and FAA will obtain feedback on ALPHA performance in a region with
frequent convection and ICI events, enabling further improvements to the ALPHA scientific
algorithms. Results are expected to inform a decision on provision of a fully operational HIWC
nowcasting product and progress the development on an international capability for HIWC
detection and forecasting that may be required by ICAO in the future.WMO Aeronautical Meteorology Scientific Conference 2017
6 - 10 November 2017
Centre International de Conférences - Météo-France - Toulouse - France
This research is in response to requirements and funding by the Federal Aviation
Administration (FAA). The views expressed are those of the authors and do not necessarily
represent the official policy or position of the FAA.
References
Haggerty, J., F. McDonough, J. Black, G. Cunning, G. McCabe, M. Politovich, C. Wolff, "A
System for Nowcasting Atmosphereic Conditions Associated with Jet Engine Power Loss and
Damage Due to Ingestion of Ice Particles," AIAA Atmosphere and Space Environment
Conference, New Orleans, USA, June 2012.
Mason, J.G., J.W. Strapp, and P. Chow, “The ice particle threat to engines in flight,” 44th AIAA
Aerospace Sciences Meeting, Reno, Nevada, 9-12 January 2006, AIAA-2006-206.
Potts, R.J., Keenan, T.D. and May, P.T., "Radar characteristics of storms in the Sydney area",
BMRC Research Rep. 72, 1999, 25pp.
Puri, K., and Coauthors, 2013: Implementation of the initial ACCESS numerical weather
prediction system. Aust. Meteorol. Oceanogr. J., 63, 265–284.
Rugg, A., J. Haggerty, G. McCabe, R. Palikondra, and R. Potts, High ice water content
conditions around Darwin: Frequency of occurrence and duration as estimated by a nowcasting
model,” AIAA Atmosphere and Space Environment Conference, Denver, USA, June 2017.
Strapp, J. W., and Coauthors, 2016: The High Ice Water Content (HIWC) study of deep
convective clouds: Report on science and technical plan. FAA Rep. DOT/FAA/TC-14/31, 105 pp.
[Available online at www.tc.faa.gov/its/worldpac/techrpt/tc14-31.pdf.]You can also read
