Groundbased and Spacebased Radar Precipitation Imaging

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Ground-based and Space-based Radar Precipitation
Imaging V.Chandrasekar Colorado state
University January 28, 2008
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• Introduction
• CSU-CHILL radar
• - PPI (Plan Position Indicator) scan
• - RHI (Range Height Indicator) scan
• Tropical Rainfall Measurement Mission (TRMM)
• - Precipitation Radar (PR)

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CSU-CHILL radar New antenna installation
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Example of PPI scan
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Example of RHI scan
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The received signal corresponds to resolution
volume determined by the transmit pulse width
beam width

• Backscattered signal in weather radars is from
  distributed target
• Cross range resolution is dependent on the
  antenna beam width and range

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Waveform Coding at CSU-CHILL radar

• Intrinsic backscattering properties of
  hydrometeor in a linear polarization basis
  enables the measurements such as size, shape and
  spatial orientation

• Intrinsic backscattering properties of
  hydrometeor is described by the backscattering
  covariance matrix

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Waveform Coding at CSU-CHILL radar
Backscattered signal from horizontal polarization
Backscattered signal from vertical polarization

• Backscattering covariance matrix is given by

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Waveform Coding at CSU-CHILL radar

• The received signal in the two polarization
  channels can be written as

• The covariance matrix of the received signal is
  given by

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Waveform Coding at CSU-CHILL radar
Reflectivity from (a) Alternate mode (203400
UTC) (b) Walsh coded simultaneous mode (202851
UTC). Data collected by CSU-CHILL on May 29, 2007
LDR estimated from (a) Alternate mode (203400
UTC) (b) Walsh coded simultaneous mode (202851
UTC). Data collected by CSU-CHILL on May 29, 2007
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Networked System Processing
KSAO
KCYR
KRSP
KLWE
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Networked System Processing
Tornadic circulation feature wind speeds greater
than 40 m/s (90 mph)
UNFILTERED
FILTERED
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Networked System Processing
Measurement at each radar node
Networked retrieval
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Reflectivity retrieval in a networked radar
environment Demonstration from IP-1 radar network
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Before
After
KTLX
May 7, 2007 CSE
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Before
After
KTLX
May 8, 2007 CSE
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TRMM-PR orbital and observatory characteristics

• TRMM Tropical Rainfall
• Measurement Mission
• - Joint mission between NASA and JAXA
• - Observing precipitation over tropical
  regions
• between 37oS and 37oN
• - Satellite was lunched in 1997

• PR Precipitation Radar (installed on TRMM)
• - 13.8 GHz Ku-band radar
• - Horizontal resolution at nadir
  4.3 km.
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  ( 5 km. postboost)
• - Range resolution 250 m.
• - Swath width 215 km. ( 245 km
  postboost)
• - Altitude 350 km. ( 402.5 km
  postboost)
• Note TRMM was boosted in altitude in
  August 2001

A hurricane in TRMM-PR track
215 km.
(Adopted from TRMM data user handbook, 2001)
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Ground and Space-based radar volume matching

• Performance and system cross validation

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Geometry of pulse volume and resolution
degradation effect of space-based radar
measurement.
Effective vertical resolution xr xb

hcos? r ?B sin ?
Effective horizontal resolution hr hb

hsin? r ?B cos ?
to surface
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Geometric distortion in the space-base radar
image caused by platform motion
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Difference in resolution between space and
ground-based radar images

• A couple example from simultaneous observations
  between NEXRAD and TRMM

TRMM-PR
NEXRAD KAMX Miami, FL
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TRMM-PR
NEXRAD KEVX , Red Bay/Eglin, FL
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3-D volume matching and shifting based on GR and
SR resolution volumes
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Matched and Aligned images between SR and GR
GR
SR
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Matched images of a tropical storm in Bay of
Bengal
GR (SHAR, India)
SR (TRMM-PR)
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Summary

• The Radar research group works on a variety of
  problems all the way from
• Design and development of imaging sensors
• Analysis of images for interpretation and
• Cross validation of images from multiple
  platforms
• Developing hardware, theory algorithms and and
  novel applications