In-Flight Icing Products In-Flight Icing Products for Helicoptersfor Helicopters

Ben C. BernsteinBen C. BernsteinNational Center for Atmospheric ResearchNational Center for Atmospheric ResearchIn-flight Icing Product Development TeamIn-flight Icing Product Development Team

FAA – Aviation Weather Research ProgramFAA – Aviation Weather Research Program

In-Flight IcingIn-Flight IcingEncounters with supercooled liquid waterEncounters with supercooled liquid water– Liquid water at T < 0Liquid water at T < 0ooCC

Ram air rise, depending on aircraft speedRam air rise, depending on aircraft speed– CloudsClouds– Precipitation (FZDZ, FZRA) – SLDPrecipitation (FZDZ, FZRA) – SLD

Most helicopters are not certified for icingMost helicopters are not certified for icing– Avoidance is the focusAvoidance is the focus

Clouds, precipitation at T < 0Clouds, precipitation at T < 0ooC (+10C (+10ooC & vis moist – engine)C & vis moist – engine)– Some have ice protectionSome have ice protection

Good to avoid icingGood to avoid icingIf you’re going to encounter itIf you’re going to encounter it

– Where will it be (3-D space)Where will it be (3-D space)– When will it be there?When will it be there?– How likely is it?How likely is it?– Will there be large drops? Certification is for small drop icing.Will there be large drops? Certification is for small drop icing.– How severe will it be?How severe will it be?

IFIPDT Products – CIP & FIPIFIPDT Products – CIP & FIPCurrent Icing Product (CIP)Current Icing Product (CIP)– Hourly diagnoses of icing, blending info from many sourcesHourly diagnoses of icing, blending info from many sources

20km horizontal spacing CONUS & surroundings20km horizontal spacing CONUS & surroundings1000ft (305m) vertical spacing1000ft (305m) vertical spacingIcing Probability – Chance of ANY icing (avoidance)Icing Probability – Chance of ANY icing (avoidance)SLD “Potential” – Uncalibrated chance of large dropsSLD “Potential” – Uncalibrated chance of large dropsIcing Severity – Categorical (trace, light, mod, heavy)Icing Severity – Categorical (trace, light, mod, heavy)

– Fully operational Dec 2006, pending approvalFully operational Dec 2006, pending approvalWill be usable by pilots, dispatchers, meteorologistsWill be usable by pilots, dispatchers, meteorologists

– Current operational versionCurrent operational versionIcing “Potential”, SLD “Potential” - on Operational ADDS (Thompson)Icing “Potential”, SLD “Potential” - on Operational ADDS (Thompson)Severity available on Experimental ADDSSeverity available on Experimental ADDS

Forecast Icing Product (FIP)Forecast Icing Product (FIP)– Forecasts out to 12 hours, updated every 1-3 hoursForecasts out to 12 hours, updated every 1-3 hours– Operational Products: Icing Potential, SLD PotentialOperational Products: Icing Potential, SLD Potential

Experimental Severity in March 2007, Operational Fall 2008Experimental Severity in March 2007, Operational Fall 2008

Alaskan versions – Experimental. Operational: FY09, FY10Alaskan versions – Experimental. Operational: FY09, FY10

The CIP Concept

PIREPSLIGHTNING (NLDN)

MODEL (RUC)

SURFACE OBS (ASOS, etc)

RADAR (NEXRAD)

SATELLITE (GOES)

CONFIDENCEWEIGHT

CONTEXT

MEANING

VALUE

200km

+/-

400

0ft

LAST 2 HR

xy, z, t WEIGHTED &

BLENDED SEVERITY

AND CONFIDENCE

POS & NEG

x=20km z=1000ft

GRID

SPACE & TIME WEIGHTED PIREPS

BLENDED SATELLITE IMAGERY ALBEDO & CHANNEL 2-4

SITUATIONAL APPLICATION OF RADAR REFLECTIVITY

STABILITY DAMPED LWC CALCULATION

SITUATION

STRUCTURE

ciwivi

ciwi

DAMPING

VIS CH2-4

SAT-COMBO

0.00

0.25

0.50

0.75

1.00

0 10 20 30 40

Reflectivity (dBZ)

Inte

res

t

All SnowCold Rain or Above Warm NoseWarm Rain (CTT>-12 w/liquid) or CTT<-12 with DZ or Freezing Precip

PKBARR ARR

PKB

CIP’s adiabatic-q field @6k (~825mb)

SEVERITY6000 ft

Raw Categorical

88

55

Model (T, RH, VV, SLW) Satellite METARs Radar PIREPs

Step 1: Place datasets onto a common grid

Step 2: Find the 3-D locations of clouds and precipitation

Multiple cloudlayers

Single-layercloud

Cloud toptemperature

gradient

Classicalfreezing

rain

Icing Probability, SLD Potential, Icing Severity

ICING=0.0SLD=0.0

Severity=None

Lightning

Deepconvection

Step 3: Apply fuzzy logic membership functions to icing-related fields to create interest maps

None?

Step 4: Determine the physical icing scenario using a decision tree

Step 5: Situationally calculate the initial icing , SLD potential and Icing Severity

Step 6: Boost initial values using VV, SLW, PIREPs, satellite, radar, etc. Regular Gridded Field Irregular Field

Processing/Analysis Decision Tree

Results

The CIP ProcessThe CIP Process

Model (T, RH, VV, SLW) Satellite METARs Radar PIREPs

Step 1: Only use the model grid

Step 2: Find the 3-D locations of clouds and precipitation

Multiple cloudlayers

Single-layercloud

Cloud toptemperature

gradient

Classicalfreezing

rain

Icing Probability, SLD Potential, Icing Severity

ICING=0.0SLD=0.0

Severity=None

Lightning

Deepconvection

Step 3: Apply fuzzy logic membership functions to icing-related fields to create interest maps

None?

Step 4: Determine the physical icing scenario using a decision tree

Step 5: Situationally calculate the initial icing , SLD potential and Icing Severity

Step 6: Boost initial values using VV, SLW, PIREPs, satellite, radar, etc. Regular Gridded Field Irregular Field

Processing/Analysis Decision Tree

Results

The FIP ProcessThe FIP Process

Examples of CIP (Icing Probability)Examples of CIP (Icing Probability)

• Unprotected

• Any chance of icing = no go?

• Protected

• Where do you draw the line?

• Mission dependent?

• Visible moisture (T < +10oC)

Examples of CIP (SLD Potential)Examples of CIP (SLD Potential)

• Protected, but not for SLD!

• Any chance of SLD icing = no go?

Examples of CIP (Icing Severity)Examples of CIP (Icing Severity)

• Unprotected

• Trace or higher = no go?

• Protected

• Where do you draw the line?

• Put icing into context of other things

• C/V, winds, turb, traffic, MVAs

Thank YouThank You

Ben C. BernsteinBen C. BernsteinIFIPDT Alternate LeadIFIPDT Alternate Leadbernstei@rap.ucar.edubernstei@rap.ucar.edu

(303) 497-8424(303) 497-8424