measuring in -cloud turbulence€¦ · measuring in -cloud turbulence: the nexrad turbulence...

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Measuring In Measuring In - - cloud Turbulence: cloud Turbulence: The NEXRAD Turbulence Detection Algorithm The NEXRAD Turbulence Detection Algorithm John K. Williams John K. Williams , Greg , Greg Meymaris Meymaris , Jason Craig, Gary Blackburn, , Jason Craig, Gary Blackburn, Wiebke Wiebke Deierling Deierling , and Frank McDonough , and Frank McDonough AMS 15 AMS 15 th th Conference on Aviation, Range and Aerospace Meteorology Conference on Aviation, Range and Aerospace Meteorology Los Angeles, CA Los Angeles, CA August 1, 2011 August 1, 2011

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Page 1: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

Measuring InMeasuring In--cloud Turbulence: cloud Turbulence:

The NEXRAD Turbulence Detection AlgorithmThe NEXRAD Turbulence Detection Algorithm

John K. WilliamsJohn K. Williams, Greg , Greg MeymarisMeymaris, Jason Craig, Gary Blackburn, , Jason Craig, Gary Blackburn,

WiebkeWiebke DeierlingDeierling, and Frank McDonough, and Frank McDonough

AMS 15AMS 15thth Conference on Aviation, Range and Aerospace MeteorologyConference on Aviation, Range and Aerospace Meteorology

Los Angeles, CA Los Angeles, CA

August 1, 2011August 1, 2011

Page 2: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

What is the NTDA?

• The NEXRAD Turbulence Detection Algorithm uses Doppler weather radar data to measure turbulence in clouds, complementing radar reflectivity.

NEXRAD

Page 3: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

What does NTDA measure?

• Atmospheric turbulence: eddy dissipation rate (EDR), ε1/3, m2/3 s-1

– EDR can be converted to the impact on an

aircraft (RMS-g) based on the aircraft type and

flight parameters

• Uses spectrum width, which represents radial

wind variability within the measurement volume

• NTDA only measures turbulence where sufficient wind-tracing reflectors exist, i.e., in clouds and storms

– Focus on in-cloud convectively-induced

turblence

Page 4: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How rapidly does NTDA update?

• NTDA runs on each sweep of NEXRAD data

as it becomes available

• Regions are rescanned every 4 – 8 minutes depending on the volume coverage pattern (VCP) being employed

• Our real-time 3-D mosaic currently runs every

5 minutes, but that’s configurable

– Mosaic algorithm “pushes” measurements onto

a 3-D grid, minimizing gaps between sweeps

Page 5: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How fast does turbulence evolve?

• Moderate or severe turbulence in storms may

appear quickly and last as little as a few minutes

CIDD research display: NTDA mosaic 6-hr loop

on 11 August 2008, 36,000 ft.

Overlaid are in situ EDR measurements from

United Airlines B-757s

Null

Light

Mod

Sev

Page 6: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How can NTDA data be used?

• Tactical decision support for en-route aircraft– Improve situational awareness, airspace

utilization, and safety.

– May help obviate the need for “pathfinder”aircraft after airspace closures

• Measurements may be assimilated into turbulence nowcasts

• May be used as verification “truth” data for turbulence forecasts

• Provides a tool for investigating storm dynamics and turbulence climatology

Page 7: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

What is the status of NTDA?

• NTDA-1 demonstrated in real-time 2005 –

2007

– Displayed to dispatchers and en-route uplinks

• NTDA-1 deployed as part of NEXRAD Open Radar Products Generator Build 10 in 2008

• CONUS NTDA processing and 3-D mosaic running at NCAR since 2008

– Test deployment to Aviation Weather Center in

September 2010

• NTDA-2.5 (dual-pol capable) is being tested

– Possible 2012 deployment

Page 8: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

• Contaminated data (sun spikes, artifacts) are

detected and censored

• SW measurement quality

assessed via fuzzy logic, based on– Operational mode for that sweep

– Signal-to-noise ratio (SNR)

– Overlaid Power Ratio (PR)

– Clutter and overlaid clutter

contamination

– Insect contamination

• SW is “scaled” to EDR:

• Local confidence-weighted averages are computed

How does NTDA work?

Theoretical NEXRAD “scaling” function, f(r)

raw 0EDR ( ) SW( ) ( , )r r f r L=

Example confidence “interest maps”

Page 9: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How has NTDA beenimproved?

• Code faster and uses

less computer memory

• Supports NEXRAD changes (super-resolution, Sachi-Zrnicphase coding, multi-

PRF VCPs, dual-pol)

• Provides improved coverage thanks to more refined quality

control, e.g., based on SNR

KVNX, 20110511 0050 UTC, 3.4 degNTDA-2.5

KVNX, 20110511 0050 UTC, 3.4 degNTDA-1

NT

DA

ED

RN

TD

A E

DR

Page 10: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How did the SNR QC improve?

• Replaced previous interest maps that were based on

“worst case” for each VCP

• Now compute maps “on the

fly” based on exact operational mode (from

metadata that accompanies the NEXRAD sweep data)

• Many future NEXRAD changes (e.g., new SW

estimation method) may now be handled via

simulation database update

NEXRAD Simulation

Database

NEXRAD Simulation

Database

Operational mode

(N, Ts, etc.), range gate,

performance requirements

Operational mode

(N, Ts, etc.), range gate,

performance requirements

SNR-to-confidence

interest map

SNR-to-confidence

interest map

Performance dataPerformance data

Page 11: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

null

(0-1)

light

(1-3)

moderate

(3-5)

severe or

greater (> 5)

(at r = 70 km)

SNR = 30 dB

SNR = 10 dB

Example: simulation results for VCP 12 N = 40 pulses, Ts = 988μμμμs, SW = 0.5 m s-1, 5000 runs

coun

tscoun

ts

Measured spectrum width

Page 12: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How well does NTDA work?

• Evaluated via

– Field program data

– Comparisons with in

situ EDR data

– Case studies, including accidents

– Airline dispatcher feedback

– Pilot feedback

• NTDA appears to

work well, subject to limitations

NTDA EDR vs. aircraft EDR from NASA B757 flight tests (2002)

ROC skill curves for light, moderate,

severe and extreme turb.

Page 13: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

What are some limitations of NTDA?

• Coverage is poor near the

ground

• Thin shear layers and other phenomena may cause spurious high measurements

• Does not adjust for hydrometeor inertial effects

• Does not detect organized air motions that can also

upset aircraft

NTDA 0015 UTC, FL 330

NTDA 0030 UTC, FL 330

United 967 turb. encounter,

21 July 2010 00:14 UTC

Page 14: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How will NTDA fit into NextGen?

• NTDA 3-D mosaics may be included in the “4-

D data cube”

• NTDA 3-D mosaic data are assimilated into the Graphical Turbulence Guidance Nowcast

• May be a candidate for Weather Technology in the Cockpit demonstration

4D Wx

SAS

4D WeatherData Cube

NTDAGTG

GTGN

DCIT

Page 15: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How much does NTDA contribute to GTGN’s performance?

GTG 1hr Fcst

GTGN & Next 15min in situIn situ, PIREPs & NTDA

GTG & DCIT

Courtesy of Julia Pearson

Page 16: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

NTDA contributions to GTGNVerification via in situ EDR reports

Courtesy of Julia Pearson

• Evaluation shows that adding NTDA

considerably improves GTG Nowcasts

Prediction of Moderate or Greater Turbulence

Page 17: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

• Example: 28 September 2007 (Flight Level 300; 2 km horizontal resolution)

NTDA EDRDBZ

NTDA EDR

DBZ

How is turbulence related to reflectivity?

Page 18: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

NTDA EDR

DBZ

• Example: 28 September 2007 (3,000 ft vertical resolution)

How is turbulence related to reflectivity?

Page 19: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How is turbulence related to storm lifecycle?

Radar Reflectivity

EDREDR

Time (UTC)

All

NTDA

22 July 2010

Page 20: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

Reflectivity X-Z plot and U, W winds NTDA EDR X-Z plot

How does turbulence relate to updrafts?

Reflectivity Y-Z plot and V, W winds NTDA EDR Y-Z plot

• Example: 21 February 2005, Huntsville, dual-Doppler

Page 21: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

How is turbulence related to lightning?

• See Wiebke Deierling’s talk in this session,

2.3: “The relationship of in-cloud convective turbulence to total lightning”

Page 22: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

What are plans for NTDA?

• NTDA-2.5 testing to be completed in 2012,

system prepared for deployment to the Aviation Weather Center

• NTDA-3 would adapt to NEXRAD changes and use dual-pol information to provide low-level quality control, enabling additional coverage

• CONUS NTDA processing and 3-D EDR mosaic demonstration continue at NCAR

Page 23: Measuring In -cloud Turbulence€¦ · Measuring In -cloud Turbulence: The NEXRAD Turbulence Detection Algorithm John K. Williams , Greg Meymaris , Jason Craig, Gary Blackburn, Wiebke

Acknowledgement

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.

Contact information

John K. Williams

National Center for Atmospheric Research

[email protected]

303-497-2822