RADAR METEOROLOGYCourtney Schumacher
Texas A&M University
ATMO 352
Rinehart (2004)
“Simplified”Block DiagramOf a PulsedWeather Radar
14th floor
12th floor
Upper roof
Transmitting and Receiving Radar Waves
ww2010.atmos.uiuc.edu/(Gh)/guides/rs/rad/basics/sgnl.rxml
Properties of an Electromagnetic Wave:
: wavelengthf: frequencyc: speed of light
f = c
Stephens (1994)
Electromagnetic Spectrum
Radar Bands
Locating a Target using Radar CoordinatesAzimuth Angle Elevation Angle
(or slant range R)Distance, which is sometimes called “slant range”
ww2010.atmos.uiuc.edu/(Gh)/guides/rs/rad/basics/sgnl.rxml
Doppler phase shift and velocity (VD)Time T1
VD
Time T2
VD (1/4 wave) Doppler phase shift (D) of 90
ww2010.atmos.uiuc.edu/(Gh)/guides/rs/rad/basics/sgnl.rxml
Scattering (for particles small compared to wavelength ())
ww2010.atmos.uiuc.edu/(Gh)/guides/rs/rad/basics/sgnl.rxml
Smaller target scatters relatively less energy.
Larger target scatters relatively more energy.
Scattered Energy ~ (Diameter)6
Received Energy converted to RADAR REFLECTIVITY
Lots of targets!
Rain = many scatterers!
Cifelli et al. (2002)Wakimoto and Bringi (1988)
Polarimetric measurements
Scanning Mode: PPI
Plan Position Indicator (PPI)
CSU-CHILL S-band radarSupercell: 29 June 2000
PPI of radar reflectivity at 3.54 elevation angle
Rangerings
azimuth
Scanning Mode: RHI
Range Height Indicator (RHI)RHI of radar reflectivity at 67.29 azimuth angle
Height(km)
Range (km)
elevationangle
NWS Weather Surveillance Radar – 1988 Doppler (WSR-88D) and NEXRAD Network
NWS Scan Strategies
VCP-11 VCP-21
Range (km) Range (km)
Hei
ght
(km
)
14 tilts5 min
9 tilts6 min
• VCP-12 has 4 min update with more resolution at lower levels
Radar examples
Hector over the Tiwi Islands, Australia
Classic Reflectivity Structure of an MCS from ADRAD
Classic Reflectivity Structure of an MCS from ADRAD
Classic Velocity Structure of an MCS from ADRAD
Classic Structure of a LL-TS MCS
www.crh.noaa.gov/lmk/soo/docu/bowecho.php
WEC=Weak echo channelRIJ=Rear-inflow jet
Bow Echo
Tornadic Supercell 9 May 2003Tornado on ground 0346Z
Tornado’s Location
Radar reflectivity
Tornado’s Location
Doppler velocity
Tornadic Supercell 9 May 2003Tornado on ground 0346Z
3 May 1999 Mesocyclone
www.nssl.noaa.gov/divisions/warning/swat/Cases/990503/StormA.html
1.4° Reflectivity PPI 23:17 UTC 5.2° Radial Velocity PPI 22:58 UTC
WSR-88D Mesocyclone Detection
Source: NOAA NSSL
1.6 km
3 May 1999 BWER
3.5 km
2.6 km
4.5 km
www.nssl.noaa.gov/divisions/warning/swat/Cases/990503/StormBG.html
4 May 1999 Vertical Structure
www.nssl.noaa.gov/divisions/warning/swat/Cases/990503/StormBG.html
0.5° Reflectivity PPI 02:36 UTC Vertical cross section 02:36 UTC
BWER, forward overhang, hail cascade
Nebraska record hailstorm 2003 70-75 dBZ
Differential Reflectivity (ZDR)Zh-Zv
Differential Reflectivity Differential Reflectivity (Z(ZDRDR))
Reflectivity (ZReflectivity (ZHH))
Hail
Rapid DOW Phased Array (NSF/CSWR facility)
• Hybrid electronic/ mechanical steering