Hong Kong Observatory - 21 March 2005 Briefing on Windshear and Turbulence Alerting Service S.T....

Hong Kong Observatory - 21 March 2005

Briefing on Windshear and Briefing on Windshear and Turbulence Alerting ServicTurbulence Alerting Servic

ee

S.T. Chan & P.W. Chan21 March 2005


Agenda

Understanding of WS & TURB in HKUnderstanding of WS & TURB in HK Freq. of occurrence Freq. of occurrence Typical conditions conducive to WS & TURBTypical conditions conducive to WS & TURB CharacteristicsCharacteristics

HKO WS & TURB alerting serviceHKO WS & TURB alerting service Recent improvementsRecent improvements How do we performHow do we perform Operational aspectsOperational aspects

Looking forwardLooking forward Q&AQ&A


What is windshear and turbulence? Windshear – sustained change in wind directiWindshear – sustained change in wind directi

on/speed for more than a few secondson/speed for more than a few seconds change in headwind/tailwindchange in headwind/tailwind change in liftchange in lift Scale several hundred metres - 4 kmScale several hundred metres - 4 km


What is windshear and turbulence?

Glide slope of aircraft on APP or DEP Glide slope of aircraft on APP or DEP typically 3 – 6 deg.typically 3 – 6 deg.->Glide path in a plane close to horizontal->Glide path in a plane close to horizontal

Systematic vertical shear (e.g. low-level Systematic vertical shear (e.g. low-level jets) not the only reason for WS jets) not the only reason for WS encounteredencountered

Most often horizontal shear (e.g. interface Most often horizontal shear (e.g. interface between different air masses) mattersbetween different air masses) matters


What is windshear and turbulence?

Turbulence – rapid irregular motion of airTurbulence – rapid irregular motion of air Rapid bumps or joltsRapid bumps or jolts effect on flight path relatively minimaleffect on flight path relatively minimal aircraft may be tossed about, momentarily aircraft may be tossed about, momentarily

out of control in severe eventsout of control in severe events


Frequency Distribution by Month

Significant windsSignificant windshear: 1 in every 5hear: 1 in every 500 flights00 flights

Significant TURB: Significant TURB: 1 in every 2,000 fli1 in every 2,000 flightsghts

1st peak

2nd peak


In Hong Kong…

5 typical weather scenarios5 typical weather scenarios Winds blowing across terrainWinds blowing across terrain

(terrain-induced)(terrain-induced) Sea breezeSea breeze Gust frontsGust fronts MicroburstsMicrobursts Low-level jetsLow-level jets

Decreasing freq. of occurrence


Winds Blowing Across Terrain Winds Blowing Across Terrain (Terrain-induced)(Terrain-induced)

Windy occasions liWindy occasions like during TC…ke during TC…

In lighter wind conIn lighter wind conditions, low-level tditions, low-level temperature inversiemperature inversion also triggers wion also triggers windshear (spring mndshear (spring months)onths)


Sea breeze Usually develops under fine weatherUsually develops under fine weather Sea breeze converges with prevailing E’liesSea breeze converges with prevailing E’lies Mostly in the form of headwind gains, but headwind losses also possibleMostly in the form of headwind gains, but headwind losses also possible


Gust front Leading edge of cool air spreading out from the Leading edge of cool air spreading out from the

downdraft of intense stormsdowndraft of intense storms Headwind gainHeadwind gain


Microburst Most violent form of downdraft from thunderstormsMost violent form of downdraft from thunderstorms Typical horizontal extent: a few kmTypical horizontal extent: a few km Inc. headwind -> Downdraft -> Inc. tailwindInc. headwind -> Downdraft -> Inc. tailwind


Low-level jet Narrow band of strong windsNarrow band of strong winds Usually affects aircraft on departure (steeper glide path)Usually affects aircraft on departure (steeper glide path) Relatively infrequent at HKIARelatively infrequent at HKIA


Characteristics of WS & TURB in HK

Most are terrain-induced Most are terrain-induced Transient and sporadicTransient and sporadic More significant on South RWY due to More significant on South RWY due to

closeness to hills in generalcloseness to hills in general Gain and loss events can co-existGain and loss events can co-exist


Windshear is Sporadic!!Windshear is Sporadic!! Small-scale disturbances Small-scale disturbances

over RWY 25L (multiple over RWY 25L (multiple events)events)

Cold colours (blue, green) – moving towards LIDAR

Warm colours (yellow, orange, pink) – moving away from LIDAR


0

5

10

15

20

25

30

-1012Distance from runway end (NM)

0

1000

2000

3000

4000

5000

6000

Hei

ght

of 6

-deg

ree

glid

e p

ath

(ft

) LID

AR

's radial velocity (k

nots)

Runway corridor 25 LD

6-degree glide path

LIDAR-Derived Headwind LIDAR-Derived Headwind ProfileProfile

RWY 25L DepartureRWY 25L DepartureHeadwind profile @ 14:41 UTC


0

5

10

15

20

25

30


0

1000

2000

3000

4000

5000

6000

Hei

ght

of 6

-deg

ree

glid

e p

ath

(ft

) LID

AR


nots)


6-degree glide path

Headwind profile @ 14:41 UTC

LIDAR-Derived Headwind LIDAR-Derived Headwind ProfileProfile

RWY 25L DepartureRWY 25L Departure


Windshear is Transient!!Windshear is Transient!!

0

5

10

15

20

25

30


0

1000

2000

3000

4000

5000

6000

Hei

ght

of 6

-deg

ree

glid

e p

ath

(ft

) LID

AR


nots)


6-degree glide path

Headwind profile @ 14:41 UTCHeadwind profile @ 14:43 UTC

Sequence of headwind changes reversed in 2 minutes!Sequence of headwind changes reversed in 2 minutes!


Gain & Loss Events Co-exist!

Gain followed by Gain followed by loss or vice versaloss or vice versa

Common for Common for terrain-induced terrain-induced casescases


Terrain-Induced MBATerrain-Induced MBA

Terrain-induced events in rain could be so stroTerrain-induced events in rain could be so strong that (i.e. loss of 30 kt or greater) TDWR captng that (i.e. loss of 30 kt or greater) TDWR captures them as MICROBURST!ures them as MICROBURST!

Don’t expect the typical sequence of events Don’t expect the typical sequence of events (gain preceding downdraft followed by loss)(gain preceding downdraft followed by loss)


WS & TURB Alerting Service


Automatic Alerts

Issued by WTWS (Issued by WTWS (WWindshear and indshear and TTurbulence urbulence WWarniarning ng SSystem) covering 3 NM from runway thresholdsystem) covering 3 NM from runway thresholds

Nominal update rate 1 min.Nominal update rate 1 min.


Automatic WS AlertsAutomatic WS Alerts

Microburst Alert (MBA)Microburst Alert (MBA) Generated by TDWR (Generated by TDWR (TTerminal erminal DDoppler oppler WWeaea

ther ther RRadar) and integrated into WTWS adar) and integrated into WTWS Runway-oriented wind speed loss >= Runway-oriented wind speed loss >=

30 kt30 kt and accompanied by precipitation and accompanied by precipitation Windshear Alert (WSA)Windshear Alert (WSA)

Runway-oriented wind speed loss or gain >= Runway-oriented wind speed loss or gain >= 15 kt15 kt


Automatic TURB AlertsAutomatic TURB Alerts

Moderate or severe in intensityModerate or severe in intensity With reference to heavy category With reference to heavy category

aircraftaircraft


Warnings Provided on ATIS

Issued by Aviation Met. ForecastersIssued by Aviation Met. Forecasters Based on pilot reports, forecasting Based on pilot reports, forecasting

rules developed from case studies, rules developed from case studies, real-time conditions as revealed by real-time conditions as revealed by TDWR, LIDAR, etc.TDWR, LIDAR, etc.


Performance of WS WarningsPerformance of WS Warnings(12-month Running Means)(12-month Running Means)

POD approaching upper limit, FAR keeps decreasingPOD approaching upper limit, FAR keeps decreasing


Improvements Implemented


New Member of WTWS New Member of WTWS Algorithms - AWAREAlgorithms - AWARE

• AWARE (Anemometer-based Windshear Alerting Rules – Enhanced) launched in mid-2004

• Replaced old LLWAS module

• Based on wind readings at 6 runway anemometers & TMT & 5 weather buoys

• Alerts out of ground truths

TMT

Weatherbuoys

Runway anemometers

Weatherbuoy


Merits of AWARE…Merits of AWARE…

• More extensive coverage compared More extensive coverage compared with LLWASwith LLWAS

• Enhanced detection of WS associated Enhanced detection of WS associated with:with:– Sea breezeSea breeze– Gust frontGust front– Shear lineShear line

• More sensitive in depicting gain More sensitive in depicting gain events than WTWS/TDWRevents than WTWS/TDWR


Shear Line Case Shear Line Case WS Episode in July 2004WS Episode in July 2004

• WS reports over 25RA:

0530 B772 +15kt0535 A343 +15kt0546 A306 -10 to +15 kt0619 A306 +15kt0625 B773 ±10 to 15kt

• All captured by AWARECold colours (blue, green) – moving towards LIDAR



Successful Detection by AWARE Successful Detection by AWARE (Previously gone undetected with (Previously gone undetected with

WTWS)WTWS)


AWARE – Point to Note

AWARE alerts updated at 10 sec. AWARE alerts updated at 10 sec. intervalsintervals

There may be brief alerts lasting a There may be brief alerts lasting a few sec. in marginal casesfew sec. in marginal cases

They are genuine alerts!They are genuine alerts!


LILIght ght DDetection etection AAnd nd RRanginganging((LIDARLIDAR) system – Fully Operational in Mi) system – Fully Operational in Mi

d-2004d-2004

Installed in mid-2002Installed in mid-2002IR (2 IR (2 μμm) → eye-safem) → eye-safe

LIDAR ScannerLIDAR Scanner

ATCX Building Roof-top


How the LIDAR works …How the LIDAR works …

100


Merits of LIDAR…Merits of LIDAR…

• Demonstrated capability in WS detection in Demonstrated capability in WS detection in non-rainy conditions non-rainy conditions -> indispensable reference tool for issuance -> indispensable reference tool for issuance of forecaster WS warnings on ATISof forecaster WS warnings on ATIS

• Better definition on location of WS detectedBetter definition on location of WS detected-> runway-specific WS warnings-> runway-specific WS warnings

• Automatic windshear detectionAutomatic windshear detection-> new alerting algorithms developed-> new alerting algorithms developed


Windshear algorithms for automatiWindshear algorithms for automatic alerting based on LIDAR datac alerting based on LIDAR data

• Adaptation of TDWR approach (shear Adaptation of TDWR approach (shear along radar beams) – the radial shear along radar beams) – the radial shear algorithmalgorithm

• Direct view of glide paths – glide-path scan Direct view of glide paths – glide-path scan windshear algorithmwindshear algorithm


Radial shear algorithmRadial shear algorithmShear line identified by algorithmShear line identified by algorithmShear line discernible on Shear line discernible on

LIDAR velocity pictureLIDAR velocity picture

Shear lineShear line


Glide-Path Scan WS AlgorithmGlide-Path Scan WS Algorithm

• ““Tube” cross-section:Tube” cross-section:

2000 feet x 400 feet2000 feet x 400 feet• Only points within the Only points within the

“tube” will be “tube” will be consideredconsidered

• Points closest to the Points closest to the flight path will be used flight path will be used to create the headwind to create the headwind profileprofile


Glide-Path Scan WS Algorithm Glide-Path Scan WS Algorithm

• SuccessfuSuccessful l detection detection of a sig. of a sig. gain gain eventevent


Trial Operation of LIDAR-based Trial Operation of LIDAR-based Alerting AlgorithmsAlerting Algorithms


Runway-specific WS Runway-specific WS WarningsWarnings(on ATIS)(on ATIS)

• LIDAR/TDWR/wind sensors, etc., LIDAR/TDWR/wind sensors, etc., reveal weather systems conducive to reveal weather systems conducive to WSWS

• Weather systems moving and Weather systems moving and evolving slowly?evolving slowly?

• WS affects only certain runway WS affects only certain runway corridors -> runway-specific warning corridors -> runway-specific warning issued issued (e.g. warning for APP corridors only)(e.g. warning for APP corridors only)-> more specific and accurate -> more specific and accurate warningswarnings


Example - Spring Easterly Example - Spring Easterly FlowFlow

(Terrain-induced)(Terrain-induced)Gap flows only Gap flows only affect southern affect southern corridorscorridors

→ → ATIS ATIS windshear windshear warning issued warning issued for southern for southern corridors onlycorridors onlyCold colours (blue, green) – moving towards LIDAR



Example - Sea BreezeExample - Sea Breeze

Sea breeze front over Sea breeze front over western corridorswestern corridors→ → ATIS windshear warATIS windshear warning will be issued for ning will be issued for all western corridorsall western corridors

Sea breeze front

Background flow

Sea Breeze


Example - Autumn/Winter Example - Autumn/Winter Northerly FlowNortherly Flow

Gap flows extend Gap flows extend to affect eastern to affect eastern approach approach corridor of north corridor of north runway onlyrunway only

→ → ATIS windshear ATIS windshear alert will be alert will be issued for that issued for that corridorcorridor

Gap Flow


Some Operational Aspects


Revision to WS/TURB Info on Revision to WS/TURB Info on ATISATIS

(Ref.: AIC 03/05)(Ref.: AIC 03/05)• Wef 27 January 2005Wef 27 January 2005• New terminology: New terminology: ““FORECASTFORECAST”” (“EXPECT” (“EXPECT”

previously) for forecast warnings by HKO. previously) for forecast warnings by HKO. ““FFORECAST AND REPORTEDORECAST AND REPORTED”” for warnings confi for warnings confirmed by pilot reports.rmed by pilot reports.

• Estimated 2 500 ft wind based on hilltop wind Estimated 2 500 ft wind based on hilltop wind on Lantau be given (Arrival ATIS) when wind son Lantau be given (Arrival ATIS) when wind speed reaches 35 kt:peed reaches 35 kt:“2500 ft estimated wind 160 degree 40 kt”“2500 ft estimated wind 160 degree 40 kt”


New Format of WS/TURB Info New Format of WS/TURB Info in Local Routine Report / MET in Local Routine Report / MET

PagePage• Revised WS/TURB Revised WS/TURB

warning terminology warning terminology under “ADDN INFO” under “ADDN INFO” following new ICAO following new ICAO templatetemplate

• New “ATIS WS/TURB New “ATIS WS/TURB WRNG” contains WRNG” contains consolidated warnings consolidated warnings for inclusion in ATIS for inclusion in ATIS

• ““FCST AND REP” for FCST AND REP” for warnings validated by warnings validated by pilot reportspilot reports


• Very common to have multiple occurrences of WS on same corridor in HK

• WTWS consolidates multiple events into ONE integrated alert– TDWR alerts higher priority than WTWS

alerts– Sinking shear (loss events) higher

priority than lifting shear (gain events)– Max intensity given in alerts

Alert PhraseologyAlert Phraseology


• E.g. APP to RWY 25L

• ‘Caution Microburst Minus 30 knots on final approach’ (instead of specific location as in US)

• Note: – The max intensity (-30 kt) can occur anywhere along the c

orridor– First encounter (+15 kt @ 3NM) not the worst encounter (-

30 kt @ 1NM)


-30 +15RWY 25L


• E.g. APP to RWY 25L

• ‘Caution Windshear Minus 15 knots on final approach’

• Note: – Some may report -15 kt, while others +20 kt (especially th

ose who conducted a missed APP on encounter of the lifting shear)


-15 +20RWY 25L


Looking Forward

Validation and tuning of LIDAR-based alerting algorithms – integration with WTWS

Backup LIDAR Uplink of WS & TURB

information to cockpit


Validation and Tuning ofValidation and Tuning ofLIDAR-based Alerting LIDAR-based Alerting

AlgorithmsAlgorithms

• Case study 28-Case study 28-30 Aug 200430 Aug 2004

• Strong Strong southerly flow southerly flow across Lantauacross Lantau

• ~70 WS ~70 WS reports during reports during the episodethe episode


PerformancePerformanceRunway

Items 25RA 25LD 25LA

Number of aircraft windshear reports 42 25 4

Number of hits 31 24 4

Probability of detection (hit rate) 0.74 0.96 1.00Number of null reports with alerts 7 7 0

False alarm rate 0.23 0.29 0.00Total alert duration (minutes) 730 1757 925

Alert duration per hit (minutes) 24 73 231


Limitations of the LIDAR in Limitations of the LIDAR in windshear detectionwindshear detection

• Not enough range coverage in Not enough range coverage in humid/rainy situationshumid/rainy situations

• ‘‘Dead zone’ with no LIDAR data Dead zone’ with no LIDAR data (about 400 m from the LIDAR)(about 400 m from the LIDAR)

• Misses of WS events between re-Misses of WS events between re-visits of scans – visits of scans – WS is transientWS is transient

• Delay in relay of alerts (data to Delay in relay of alerts (data to alerts to pilots) – out of phase alerts to pilots) – out of phase alertsalerts


• Windshear algorithm is verified against pilot Windshear algorithm is verified against pilot reports of windshearreports of windshear

• If in doubt, flight data will be obtained and aIf in doubt, flight data will be obtained and analyzed nalyzed

• More pilot reports (details as intensity and loMore pilot reports (details as intensity and location) are required to help tuning windsheacation) are required to help tuning windshear algorithmsr algorithms

• HKO needs your help! Keep reporting to us HKO needs your help! Keep reporting to us WINDSHEARWINDSHEAR or or NO WINDSHEARNO WINDSHEAR

Tuning of LIDAR-basedTuning of LIDAR-basedWS AlgorithmWS Algorithm


Current LIDAR locationBackup LIDAR location – Northern Fire Station

Backup LIDARBackup LIDAR


Backup LIDARBackup LIDAR

• To backup existing LIDARTo backup existing LIDAR• To improve coverage over the north To improve coverage over the north

runwayrunway• Funding approvedFunding approved• Installation scheduled in late 2006Installation scheduled in late 2006


Uplink of WS & TURB Info to Uplink of WS & TURB Info to CockpitCockpit

• For immediate attention of the pilotsFor immediate attention of the pilots• WS & TURB alerts most-wanted WS & TURB alerts most-wanted

information in cockpit according to a information in cockpit according to a recent survey of pilots’ viewsrecent survey of pilots’ views

• Graphical products to be developed Graphical products to be developed by HKO for future uplink applicationsby HKO for future uplink applications


International RecognitionInternational Recognition

International Federation of International Federation of Airline Pilots Association Airline Pilots Association

(2002)(2002)

International Civil International Civil Aviation OrganizationAviation Organization

(2003)(2003)

World Meteorological World Meteorological OrganizationOrganization

(2004)(2004)


Finally…Finally…

We are working on further reduction of false warnings while maintaining high hit rate

Closer coordination with ATC Continue to appeal for assistance from pilo

ts in providing reports to ATC via voice / HKO via pilot report form: http://www.weather.gov.hk/aviat/amt_e/report_form.pdf


THANK YOU!

S.T. ChanS.T. [email protected]@hko.gov.hkTel: (852) 2926 8434Tel: (852) 2926 8434Fax: (852) 2375 2645Fax: (852) 2375 2645

P.W. ChanP.W. [email protected]@hko.gov.hkTel: (852) 2926 8331Tel: (852) 2926 8331Fax: (852) 2375 2645Fax: (852) 2375 2645

Hong Kong Observatory - 21 March 2005 Briefing on Windshear and Turbulence Alerting Service S.T....

Documents

Transcript of Hong Kong Observatory - 21 March 2005 Briefing on Windshear and Turbulence Alerting Service S.T....