COST 727 Action

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COST 727 Action

COST European Cooperation in Science and
Technology
Measuring and forecasting atmospheric icing on
structures
Alain Heimo Meteotest, Switzerland MC
Chairman/COST727
COST is one of the longest-running instruments
supporting co-operation among scientists and
researchers across Europe.
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Atmospheric icing Why is it a problem?
Atmospheric icing causes severe financial losses
and reduces security and human safety -
Power line transmission
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Spain 2002
Germany 2005
Norway 1961
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Atmospheric icing Why is it a problem?

• Atmospheric icing causes severe financial losses
  and reduces security and human safety
• Power transmission
• Icing of structures (e.g.TV- and
  telecommunication towers, ski-lifts) ...

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Design of loads, safety, operational stops..
On TV-towers the ice load may be several tens of
tons.
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Atmospheric icing Why is it a problem?

• Atmospheric icing causes severe financial losses
  and reduces security and human safety
• Power transmission
• Icing of structures (e.g.TV- and
  telecommunication towers, ski-lifts)
• Telephone lines, Forest economy...

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Ice load high winds !
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Atmospheric icing Why is it a problem?

• Atmospheric icing causes severe financial losses
  and reduces security and human safety
• Power transmission
• Icing of structures (e.g.TV- and
  telecommunication towers, ski-lifts)
• Power lines, Telephone lines, Forest economy
• Wind turbines...

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• Uncertainities in prediction of production
• Additional loads /design
• Safety falling ice, operational safety
• Reduction in power production due to
• reduced lift
• shut-down
• mechanical
• failures
• iced wind
• sensors

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Atmospheric icing Why is it a problem?

• Atmospheric icing causes severe financial losses
  and reduces security and human safety
• Power transmission
• Icing of structures (e.g.TV- and
  telecommunication towers, ski-lifts)
• Power lines, Telephone lines, Forest economy
• Wind Power production
• Aviation ...

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Icing at airports and in the air
No icing
Icing
source http//meted.ucar.edu
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Atmospheric icing former activities
WMO/CIMO Wind Instrument Intercomparison Mont
Aigoual, France, 1992-1993 Organized by France,
Switzerland WMO Participating countries
11 Instruments tested 26
Jungfraujoch, Switzerland

• Conclusions from the final report
• The formation of ice makes almost all the
  calculated parameters incoherent.
• We have not been able to characterize the
  icing phenomena from ice detectors.
• It appears difficult to be both accurate and
  rugged for severe icing.

Jungfraujoch, Switzerland
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Atmospheric icing former activities

• EUMETNET SWS-II (2000-2003)
• Goal
• Acquisition of meteorological data under icing
  conditions in Finland (Luosto), France (Mt.
  Aigoual) and Switzerland (Säntis)
• Measurement period 1.10.2001 to 30.4.2002

Luosto, finland
Conclusions and recommendations - . Already
during the installation and test period
proceeding the experiment, it was quickly
recognized that the lack of adequate instruments
for the characterization of ice accretion would
represent a serious drawback for the whole
experiment. - it is important that more care
is given within the meteorological community to
produce accurate measurements under harsh
conditions and to promote measurements of icing.
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COST 727 Main Objectives (MoU 2004)

• to develop the understanding of icing
• (especially in-cloud icing) and freezing rain
• in the atmospheric boundary layer (ABL)
• to produce information on distribution of
• icing over Europe
• to improve the potential to
• observe icing
• monitor icing
• forecast icing

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Participating countries
Non-COST Participant Japan (Kanagawa Institute
of Technology)
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Objectives

• To develop scientific understanding of icing
  processes together with modeling and forecasting
  of icing.
• Measurements
• To compile existing sources of icing data in
  Europe
• To harmonize ongoing measurement programs in
  Europe
• To fulfill the WMO/CIMO request to provide
  guidance for performing measurements under harsh
  icing conditions.
• To promote the development of robust, rugged
  icing detectors to be deployed at automatic
  meteorological stations as well as at other sites
  where icing effects may be critical. Simple
  sensors delivering a yes/no information are
  needed as well as more sophisticated instruments
  yielding values of ice thickness/weight, types of
  ice.
• Modelling
• To develop numerical meteorological models for
  icing studies with improved icing
  parameterizations and verification of icing
  models with ground-truth data.
• To perform climatological icing studies and
  mapping of icing severity

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Measurements of icing

• Achieved during the last 2 years
• Based on preliminary measurements, selection of 2
    reference  sensors for the detection of ice
  accretion (Goodrich 0847LH1) and for the
  measurement of ice loads (Combitech Mk I)

• Principle ultrasonic resonance
• promising results from earlier studies
• difficult to get it from manufacturer
  (military regulations)
• only little measurement data available

• Principle weighting of ice
• designed according to ISO 12494 definition
• operational from the beginning
• promising results
• design improvements needed (e.g. oscillations)

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Measurements of icing

• Achieved during the last 2 years
• Based on preliminary measurements, selection of
  2   reference  sensors for the detection of ice
  accretion (Goodrich 0847LH1) and for the
  measurement of ice loads (Combitech Mk I)
• Calibration of the  reference  instruments in
  a dedicated icing wind tunnel facility (Kanagawa
  Institute, Tokyo, Japan)

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Icing wind tunnel test
in Cryospheric Environment Simulator at Shinjo
Branch of National Research Institute for Earth
Science and Disaster Prevention
in Kanagawa Institute of Technology
lt 20m/s (with a larger test section) lt 100m/s
(in a smaller test section) gt -25 deg. Cel.
lt 20m/s (1m by 1m test section) gt -25 deg.
Cel. Sprayers not installed all the time
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Measurements of icing

• Achieved during the last 2 years
• Based on preliminary measurements, selection of 2
    reference  sensors for the detection of ice
  accretion (Goodrich 0847LH1) and for the
  measurement of ice loads (Combitech Mk I)
• Calibration of the  reference  instruments in
  a dedicated icing wind tunnel facility (Kanagawa
  Institute, Tokyo, Japan)
• Installation and operation of 6 test stations in
  Europe equipped with the Combitech Mk I
  (20072008) and the Goodrich 0847LH1 (2008)
  Luosto (Finland), Sveg (Sweden), Zinnwald
  (Germany), Deadwater Fell (United Kingdom),
  Studnice (Czech Republic) and Guetsch
  (Switzerland)

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European test stations
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Switzerland (Guetsch test station)
Czech Republic (Studnice)
Germany (Zinnwald)
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Luosto fell, Finland
Åre, Sweden
Deadwater Fell, UK
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Measurements of icing

• Achieved during the last 2 years
• Based on preliminary measurements, selection of 2
    reference  sensors for the detection of ice
  accretion (Goodrich 0847LH1) and for the
  measurement of ice loads (Combitech Mk I)
• Calibration of the  reference  instruments in
  a dedicated icing wind tunnel facility (Kanagawa
  Institute, Tokyo, Japan)
• Installation and operation of 6 test stations in
  Europe equipped with the Combitech Mk I
  (20072008) and the Goodrich 0847LH1 (2008)
  Luosto (Finland), Sveg (Sweden), Zinnwald
  (Germany), Deadwater Fell (United Kingdom),
  Studnice (Czech Republic) and Guetsch
  (Switzerland)
• Setup of the first European Icing Dataset
  containing all meteorological parameters
  necessary for icing modeling and simulation -gt
  winter 2007-2008 selection of 3 major icing
  events for each station

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Modelling icing of structures

• The theoretical basic knowledge is presently
  available, based on the ISO 12494 standards
  (Makkonen formula) and new cloud microphysics
  schemes built in the WRF model code
• Verification data are now available and
  standardized for sites located all around Europe.
  Unfortunately more data (winters) are needed.
• Preliminary results show that the current
  version of the WRF model is able to perform very
  accurate simulations of icing events at all test
  stations in Europe (especially for the collapse
  of a measurement tower in Switzerland)
• Measured site information about the Liquid Water
  content and Droplet Size Distribution are still
  missing
• Tentative simulation runs of wet snow accretion
  and freezing rain events have been started

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Numerical modeling of ice accretion

• WRF is a modern mesoscale, non-hydrostatic
  numerical weather prediction model developed
  mainly by NCAR, NOAA and NCEP (USA) designed for
  mesoscale and high resolution forecasts.
• WRF has the advantage of a very sophisticated
  calculation of clouds and precipitation.
• Applications from Large Eddy Simulations ?x
  100m
• to regional climate simulations ?x 100km.
• WRF is meant to gradually replace its
  predecessor, MM5.

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Numerical modeling of ice accretion
Following the ISO12494 standard (Atmospheric
icing of structures), the in-cloud ice accretion
on a cylinder can be expressed by the formula
where a1 Collision efficiency a2 Sticking
efficiency a3 Accretion efficiency w Mass
concentration of cloud water (LWC) A Cross
sectional area V Wind speed

• Specific input data from measurements or from 3D
  weather models
• are needed to compute a1 and a 3
• Temperature, Wind speed, humidity lt- standard
  measurements
• LWC lt- Simulated by WRF
• Median Volume Droplet size lt- unknown at present
  (fixed value assumed).

Test simulations have been carried out with the
weather model WRF extended with the above
algorithm.
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Case 1 Luosto (Finland) December 2007

• WRF simulation

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96h WRF simulation 800m grid size
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120h WRF simulation 800 m grid size
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Case 2 Schwyberg (Switzerland) November 2007

• WRF simulation

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Tower collapse at Schwyberg, Switzerland
Data acquisition failure
Ice load and strong winds -gt tower collapse
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Case 3 Mapping (tentative)28.12.2007
7.01.2008

• WRF simulation

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Activities until end of Action

• Measurements
• Continuous operation of the 6 test stations
  equipped with the 2 reference instruments
• Upgrade of the present instruments together with
  the manufacturer
• Extend dataset with the winter 2008-2009
  measurements
• Modeling
• Upgrade WRF model with updated microphysics (PhD)
• Perform simulations based on the EID
• Perform sensitivity studies with LWC and MVD

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For further details, please visit poster
P2(40) Announcement The Final Workshop of
COST-727 Action 13th International Workshop on
Atmospheric Icing on Structures IWAIS will be
held jointly in Andermatt (Switzerland) ,
8-11.9.2009 Please register at
www.IWAIS2009.ch Thank you for your attention !