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