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