Real-Time Dissemination of Real-Time Dissemination of Hurricane Wind Fields Determined Hurricane Wind Fields Determined

from Airborne Doppler Radarfrom Airborne Doppler Radar

John Gamache

NOAA/AOML/Hurricane Research Division

Collaborators: Joseph Griffin, Peter Dodge,

Nancy Griffin

Supported by NOAA Joint Hurricane Test Bed

Project GoalsProject Goals

Develop a hurricane wind-field analysis in “real time” and make it available to hurricane specialists at the Tropical Prediction Center

Send reliable observations to the Environmental Modeling Center at NCEP for assimilation testing in numerical simulations

Airborne Radar on NOAA P-3Airborne Radar on NOAA P-3

Airborne Radar

1) Scanning axis along aircraft fuselage

2) 3-cm wavelength

3) Measures reflectivity (precipitation content)

4) Measures radial velocity from aircraft

FOR MORE INFO...

http://www.aoml.noaa.gov/hrd/project2003/doppler.html

Jorgensen et al., 1983, J. Climate Appl. Meteor, 22, 744-757

Present Analysis SoftwarePresent Analysis Software

Reliable--Works on multiple platforms

Mass-conserving Consistent to within 1-2 m/s with

Doppler observations Operates in research mode– Researcher has plenty of time to make

decisions regarding errors/assumptions– Final analysis may take years

Hurricane Humberto23 Sep 20012330 UTC

Altitude: 1km

Tangential wind (m/s)Radar Reflectivity (dBZ)

And wind field

Hurricane Humberto23 Sep 20012330 UTC

Azimuth 350

Vertical cross-section oftangential and vertical windsand winds within the plane

range from center (km)0

10

35

5

10

15

Main sources of error from NOAA P-3 Main sources of error from NOAA P-3 Airborne Doppler RadarAirborne Doppler Radar

Doppler radial velocity ambiguityReflection from sea surfaceIncorrectly measured antenna

pointing directionNoise

Doppler Radial Velocity AmbiguityDoppler Radial Velocity Ambiguity

Velocities determined from radar pulse phase measurements

-180o to 180o phase range– Corresponds to a radial velocity range– P3--range from -12.9 to 12.9 up to -25.8 to

25.8 meters per second--Nyquist velocity Angles < -180o or > 180o are ambiguous– Corresponding velocity aliased or “folded”– True velocity is measured aliased velocity

plus 2 times a multiple of Nyquist velocity

NoiseNoise

Receiver Noise--power thresholdMeteorological Noise– Turbulence in boundary layer– Turbulence in outflow from convection

Reflection from sea surfaceReflection from sea surface

Main antenna lobe– Beam width vs precipitation content

Side lobe– Annular--radius is height of aircraft– Fairly weak

“Second trip”--confusion with previous pulse– High spectral width– Usually removed easily by noise edit

Antenna pointing direction errorsAntenna pointing direction errors

Pointing direction relative to aircraftAircraft attitude HRD has software to estimate these

errors

AccomplishmentsAccomplishments

Sea-surface reflection removal software developed/preliminary test

Speckle removal developed Minor bugs in present de-aliasing

removed Two-dimensional de-aliasing scheme

development begun Preliminary discussions with EMC on

structure of “superobs”

Doppler Radial Velocity

Hurricane Humberto231754 UTC23 Sep 2001

Doppler Radial Velocity

Hurricane Humberto232842 UTC23 Sep 2001

Doppler Radial Velocity

Hurricane Humberto232855 UTC23 Sep 2001

Doppler Radial Velocity

Hurricane Humberto232901 UTC23 Sep 2001

Research Quality Automatic

Comparison of Analyses Created from Research-Quality and Automatically Edited Data

At 1 km level in Hurricane Humberto 2330 UTC on 23 September 2001

Next TasksNext Tasks

Improve two-dimensional de-aliasing– Produce consistent velocities within

contiguous regions of data– Ensure overall velocity in each contiguous

region is consistent with expected hurricane flow

Next TasksNext Tasks

Begin interaction with NCEP/EMC– Determine structure of “superobs”– Begin determination of data error covariance

of Airborne Doppler radial velocity measurements

Install new software on airborne workstations for 2004 Hurricane Season

Future TasksFuture Tasks Produce test wind analysis aboard aircraft during

2004 Hurricane Season Test sending a prototype superob by end of 2004

Hurricane Season Develop analysis display for Hurricane Specialists

during “off season” Begin determination with EMC of Doppler data error

covariance Send wind analysis to specialists during 2005

Hurricane Season Continue testing superob transmission during 2005

Hurricane Season