FIP/FIS (aka IPA)Overview

Cory A. Wolff5 – 7 November 2013

NCAR Icing Research

• FAA AWRP– Late 1980’s– History of accidents and

icing incidents– Observational and

Modeling Studies– Field Programs

• CO, OH, AK, Canada, others

– Product Development• T & RH Algorithms• Added observations,

model improvements

Anchorage

Resulting in…

IPA Forecast

• Icing Probability (FIP)– Calibrated likelihood of icing conditions

• Icing Severity (FIS)– Relative amount of liquid water present

• Supercooled Large Drop (SLD) Potential– Forecast large drops in and out of precipitation

Membership Functions• Used to create interest maps• A method to get an algorithm to “think” like a

forecaster so large volumes can be covered– The interest in icing varies based on the values of

given variables

Cloud Identification• Cloud Tops– Requires at least 2

levels w/ RH > 70%– Then looks at

vertical gradients where RH > 70%• RH• VV• TotC• θe

– Combineusing interestmaps

Cloud Identification

• Cloud Bases and Layers

Cloud Base: RH > 80%

Cloud Layer: At least 3 levels < 50%

Precipitation Identification• Where is precipitation falling?– Precipitable condensate

• Sum of the three condensates in the model that can reach the surface (rain, snow, graupel) at the lowest 3 levels

• Maximum value is the precipitable condensate

– If this value is greater than 0.01 g kg-1 then precipitation is forecast

Precipitation Identification• What type of precipitation?– Decision tree scheme from Baldwin et al. (1994)• Gives forecasts of RA, SN, FZRA, and PE

– Modified to add DZ and FZDZ• CTT > -12 °C combined with surface temperature

Icing Probability• Initial Calculation– Based on T, RH, and

CTT– Interest maps provide a

likelihood of icing for a given value• Based on cloud physics

principles, but adjusted by PIREPs compared with model data

– Multiply the 3 maps together

Icing Probability• Final Calculation– Adjustments • Precipitation type

– SN and RA decrease the likelihood while others can increase it

• VV– Upward motion = boost,

downward = decrease

• SLW– If the model has any

SLW then boost the likelihood

– Why not just use SLW?

Rising AirSinking Air

Icing Probability• The previous slides resulted in an icing

potential– Uncalibrated likelihood of icing conditions

• Probability requires calibration– Study done in 2006– Based on comparisons with PIREPs in the Great

Lakes• Lots of reports

– For a diagnosis an icing potential of 1 gave an 85% chance of icing• 3 hr forecast 74%• 12 hr forecast 43%

SLD Potential• Supercooled large drops: SLW with a diameter

≥ 50 μm• Precipitating clouds– Requires a forecast of DZ, FZDZ, FZRA, or PE– These precipitation types are direct indicators of

SLD aloft• Non-precipitating clouds– Requires a CTT > -14 °C– Total condensate of at least 0.45 g m-3 (boundary

layer) or 0.15 g m-3 (non-boundary layer)– Supercooled rain water also contributes

Icing SeverityScenarios

• No Precipitation– Cloudy, but no precipitation

forecast• All Snow

– Snow is forecast• Cold Rain

– Rain is forecast• Warm Precipitation

– Collision-Coalescence forms the precipitation

– CTT ≥ -12 °C and precipitation is DZ or FZDZ

• Cold Non-Snow/Rain– Precipitation is something

other than snow or rain and the CTT < -12 °C

• Classical Precipitation Above a Melting Layer

• Classical Precipitation Below a Melting Layer

• Convection– Certain CAPE, LI, KI, and TT

thresholds must be met

Each one has different icing properties. None have the same fields applied in the same way.

Icing Severity

Icing Severity SEV = w1*i1 + …. + wn*in

w1 + …. + wn + (dw1*t_df + dw2*ctt_df + dw3*pcond_df)

where w = weight, i = interest, and dw = damping weight

• Weight– What is the influence of this field for determining SLW

production or depletion in this scenario?• 1 = very little; 5 = maximum

• SLW production terms– Moisture, VV, potential condensate, distance from cloud base,

total water path, others– Scenario specific

• SLW depletion terms– T, CTT, precipitation

Simple MapVerticalVelocity

Interest• Provides the meaning of a field’s range of values in

terms of icing severity0 = no interest1 = maximum interest

Scenario Specific MapNo PrecipitationAll SnowCold Rain

Combo MapMoisture50% RH30% Liquid Cond.20% Ice Cond.

Depletion• Extra denominator fields give information about the

depletion of SLW– Temperature

• If too cold SLW more likely to become frozen• If too warm plane’s airspeed will discourage icing• Used in all scenarios except below the warm nose and convection

– Cloud Top Temperature• Cold temperatures more ice crystals• Only applied in top 10,000 ft. of cloud• Used in all scenarios except below the warm nose and convection

– Amount of Precipitation• Indicator of ice production with increasing values• Only applied in bottom 5000 ft. of cloud• Used in all scenarios except below the warm nose, convection, and

no precipitation

Damping Membership Functions

Temperature Cloud Top Temperature Precipitable Condensate

Final Severity (0-1)

Categorical Severity(None, Trace, Light, Moderate, Heavy)

Thresholds Applied

Final Icing Severity

PerformanceForecast Lead PODy PODn Volume % # of PIREPs

3 0.80 0.54 20.1 433

6 0.75 0.43 20.2 350

9 0.73 0.55 20.1 345

12 0.60 0.54 20.2 362

15 0.73 0.53 20.3 457

18 0.74 0.49 20.3 368

Average 0.72 0.51 20.2 2315

• Based on PIREPs from February and March 2013• CONUS version is generally similar in performance

but with less volume

Plans

• IPA Forecast– Experimental version finalized: May 2014– Verification: Summer 2014– Experimental ADDS: December 2014– Operational version development: 2015+

• Experimental version of IPA Diagnosis– Experimental version: 2015

• Combined product

Cases

18 Sep 2013• UA /OV FAI320009 /TM 2125 /FL070 /TP C208 /TA M01 /IC MOD CLR• 1379539500 20130918 2125 C208 64.93 -148.09 7000 7000 7000 5 2

18 Sep 2013• UA /OV FAI320009 /TM 2125 /FL070 /TP C208 /TA M01 /IC MOD CLR• 1379539500 20130918 2125 C208 64.93 -148.09 7000 7000 7000 5 2

19 Sep 2013• UA /OV BRW /TM 1814 /FLUNKN /TP B737 /IC MOD RIME 017-008 /RM

ICGIC, RY7 BRAG• 1379614440 20130919 1814 B737 71.29 -156.77 1300 800 1700 5 1

10 Oct 2013• UUA /OV BKA343019/TM 2320/FL050/TP AT72/TA M14/IC SEVER CLEAR

050-110/RM DURC ZAN CORRECTION• 1381360800 20131009 2320 AT72 57.16 -135.72 5000 5000 11000 8 2

19 Oct 2013• UA /OV TED360016/TM 1647/FL090/TP B737/TA M08/IC LGT RIME• UA /OV TED 340030/TM 1656/FL140/TP DH8A/TA M19/IC MOD RIME

140-120 LGT RIME 120-100/RM DURGD

12 August 2013• I looked at IC4D and concentrated on the areas where it was expecting icing. There

were two areas: Northwest coastal area to the western Brooks Range. The second area was over the se panhandle.

• synoptic - A HI PRES ridge over northwest Alaska. The second area had a hi pres extends from cook inlet to southeast ak.

• FIP - In these two situations FIP was showing significant values (80+). I would not have expected that.

• Soundings didn't show a moist layer above the freezing layer. Soundings were available on awips but not on the internet.

• PIREPs• JNU UA /OV SSR090040/TM 2012/FL100/TP B737/TA M05 /IC LGT RIME

150-105/RM DURD /CWSU ZAN=• JNU UA /OV JNU /TM 2221 /FL120 /TP SR22 /SK

OVC-TOP012/OVC035-TOP048/OVC078-TOP120 /TA M05 /IC LGT RIME 100-120 /RM TOP110-120/TA 00-M05=

• ORT UUA /OV ORT114045/TM 0213/FL120/TP C120/TA M07/RM IC MOD-HEAVY RIME=

• Convection was occurring in the vicinity of the pirep for ORT/Northway

12 August 2013

31 October 2012

• A frontal system is over the gulf of Alaska, lynn Canal, central southeast north of Kake, and coastal waters of AK.

• FIP Over southeast Alaska (Eastern Gulf Coast, Coastal Southeast Alaska, Central Southeast Alaska, and Lynn Canal zones values of 50 - 90 were mainly at FL060. The values improve by 090 over Lynn Canal.

• FIS values of 50 were over these same areas at the 060 and 090 levels.

• Attached are the pireps...indicating ICING over SE Alaska. • This was so right on the money. I don't know what to say.

NICE!

31 October 2012

UA /OV JNU /TM 1443 /FL085 /TP B737 /TA M12 /IC MOD MX 085-060 /RM DURD RWY 8. MOD MX/RIME ICE 085-060. TEMP AT 060 M08. AT 085 M12UA /OV SIT290002 /TM 1536 /FL010 /TP AT72 /SK BKN-OVC010 /TB LGT-MOD /IC NEG /RM LGT-MOD TB DURING DESCENT JNU-SIT/NEG ICE DURING ENTIRE APCHUA /OV SIT160004 /TM 1633 /FL047 /TP AT72 /SK BKN-OVC012 /TA M04 /IC NEG /RM DURC/IMCUA /OV CDV /TM 1640 /FL070 /TP B190 /TA M05 /IC LGT RIME 070-035 /RM DURDUA /OV BKA/TM 1750/FL050/TP PA31/TA M04/IC LGT-MOD RIME/RM DURC 075 RATE OF ACCUMULATION IS DIMINISHING ZANUA /OV JNU100010/TM 1824/FL050/TP B737/SK TOP100/IC MOD RIME/RM DURC ICING 050-100 ZANUA /OV SIT300021 /TM 1835 /FL070 /TP B734 /TA M10 /IC LGT RIME 095-070 /RM DURD RWY 11/OVR BASSUUA /OV SSR /TM 1921 /FL080 /TP AT72 /SK OVC020-TOP110 /TA M07 /TB LGT-MOD /IC MOD RIME 080-040 /RM LGT-MOD TB DURD RY8 JNU. AIS 3MILE FINAL. TOWER DID NOT INDICATE TYPE CLD LAYERUA /OV SIT /TM 1956 /FL040 /TP C130 /IC LGT RIME 080-040 /RM DURD RWY 11/NO TEMPSUA /OV CDV /TM 1956 /FL200 /TP B190 /SK OVC040-TOP200 /IC LGT RIME /RM DURD RY9 TA UNKNUA /OV JNU /TM 1959 /FL105 /TP AT72 /SK OVC033-TOP105 /TA M15 /IC MOD RIME /RM DURD RY8. TA M01 FL033UA /OV BKA350040/TM 2000/FL085/TP C130/TA M05/IC LGT RIME 040-085/RM DURC ZANUA /OV CGL210010/TM 2004/FL100/TP AT72/SK OVC030/IC LGT RIME SFC-100/RM DURC ZANUA /OV SIT350050/TM 2027/FL100/TP PA31/SK TOP090/TA M10/IC CONT LGT RIME 050-090/RM DURC ZANUA /OV SSR035015/TM 2106/FL190/TP B734/TB NEG/IC NEG/RM DURC ZANUA /OV SSR045025/TM 2141/FL110/TP B737/TB OCNL LGT100/IC NEG/RM DURC ZANUA /OV BKA/TM 2357/FL090/TP BE20/SK OVC020 TOPS 070/TA M8 AT 6500/IC LGT RIME 065-070

Thank you for your time

• cwolff@ucar.edu• http://www.rap.ucar.edu/icing/products/fipak• http://www.rap.ucar.edu/icing/products/ic4d_form