Jan 28, 2008 Symposium on Imaging

Ground-based and Space-based Radar Precipitation

Imaging

V.Chandrasekar

Colorado state University

January 28, 2008

Jan 28, 2008 Symposium on Imaging

Introduction

• CSU-CHILL radar

- PPI (Plan Position Indicator) scan - RHI (Range Height Indicator) scan

• Tropical Rainfall Measurement Mission (TRMM) - Precipitation Radar (PR)

Jan 28, 2008 Symposium on Imaging

CSU-CHILL radar : New antenna installation

Jan 28, 2008 Symposium on Imaging

Example of PPI scan

Jan 28, 2008 Symposium on Imaging

Example of RHI scan

Jan 28, 2008 Symposium on Imaging

The received signal corresponds to resolution volume determined by the transmit pulse width

& beam width

Bcx rR : Resolution Range-Cross Backscattered signal in weather radars is from

distributed target Cross range resolution is dependent on the

antenna beam width and range

Jan 28, 2008 Symposium on Imaging

2

2ln82

2ln82ln24

BB

Be erferff

widthbeam antenna dB 3 cyclen integratio onein Azimuth

B

Jan 28, 2008 Symposium on Imaging

r0,0,0 r,, r2 Wn r

2 f 2 ,0 f 2 ,0 d

sin drd

f 2 0, f 2 0, d d

If a r,, r2 Wn r

2 f 2 ,0 f 2 ,0 d

sin drd

r0,0,0 a f 2 0, 0 f 2 0, d d

Jan 28, 2008 Symposium on Imaging

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

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

++

+

++

+

+ + ++

------- - - - 2max

cTr

Tv

4max

Waveform Coding at CSU-CHILL radar

Jan 28, 2008 Symposium on Imaging

vhS

hhS

hvS

vvS

Ev

Eh

Backscattered signal from horizontal polarization

Backscattered signal from vertical polarization

Backscattering covariance matrix is given by

2

2

2

2222

2

vvhvvvhhvv

vvhvhvhhhv

vvhhhvhhhh

BSA

SSSSSSSSSSSSSSS

Waveform Coding at CSU-CHILL radar

Jan 28, 2008 Symposium on Imaging

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

Tvvvhhvhh VVVVz

2

2

2

2

vvhvvvvhvvhhvv

vvhvhvvhhvhhhv

vvvhhvvhvhhhvh

vvhhhvhhvhhhhh

T

VVVVVVVVVVVVVVVVVVVVVVVVVVVV

EE Kzz

The covariance matrix of the received signal is given by

Dual ChannelDigital

Waveform Generator

REF OSCILLATOR

H-Transmitter

V-Transmitter

V- Receiver

H- Receiver

DuplexerSTALO

H

V

Waveform Coding at CSU-CHILL radar

Jan 28, 2008 Symposium on Imaging

Reflectivity from (a) Alternate mode (20:34:00 UTC) (b) Walsh coded

simultaneous mode (20:28:51 UTC). Data collected by CSU-CHILL on May 29, 2007

LDR estimated from (a) Alternate mode (20:34:00 UTC) (b) Walsh coded simultaneous mode

(20:28:51 UTC). Data collected by CSU-CHILL on May 29, 2007

Waveform Coding at CSU-CHILL radar

Jan 28, 2008 Symposium on Imaging

Networked System ProcessingKSAO

KRSPKLWE

KCYR

Jan 28, 2008 Symposium on Imaging

UNFILTERED FILTERED

Tornadic circulation feature; wind speeds greater than 40 m/s (90 mph)

Networked System Processing

Jan 28, 2008 Symposium on Imaging

Networked System Processing

Measurement at each radar node

Networked retrieval

Jan 28, 2008 Symposium on Imaging

Reflectivity retrieval in a networked radar environment: Demonstration

from IP-1 radar network

Jan 28, 2008 Symposium on Imaging

KTLX

Before After

May 7, 2007 CSE

Jan 28, 2008 Symposium on Imaging

May 8, 2007 CSE

KTLX

Before After

Jan 28, 2008 Symposium on Imaging (Adopted from TRMM data user handbook, 2001)

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. ( 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

215 km.

A hurricane in TRMM-PR track

TRMM-PR : orbital and observatory characteristics

Jan 28, 2008 Symposium on Imaging

Ground and Space-based radar volume matching

• Performance and system cross validation

Jan 28, 2008 Symposium on Imaging

Effective vertical resolution = xr + xb

= h*cosθ + r θB sin θ

Effective horizontal resolution = hr + hb

= h*sinθ + r θB cos θ

Geometry of pulse volume and resolution degradation effect of space-based radar measurement.

to surface

Jan 28, 2008 Symposium on Imaging

Geometric distortion in the space-base radar imagecaused by platform motion

Jan 28, 2008 Symposium on Imaging

Difference in resolution between space and ground-based radar images

NEXRAD : KAMX Miami, FL TRMM-PR

• A couple example from simultaneous observations between NEXRAD and TRMM

Jan 28, 2008 Symposium on Imaging

NEXRAD : KEVX , Red Bay/Eglin, FL TRMM-PR

Jan 28, 2008 Symposium on Imaging

3-D volume matching and shifting based on GR and SR resolution volumes

Jan 28, 2008 Symposium on Imaging

Matched and Aligned images between SR and GR

GR SR

Jan 28, 2008 Symposium on Imaging

Matched images of a tropical storm in Bay of Bengal

GR (SHAR, India)

SR (TRMM-PR)

Jan 28, 2008 Symposium on Imaging

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