Dan Satterfield, Chief Meteorologist WHNT-TV, Huntsville James-Paul Dice Meteorologist WHNT-TV Walt Peterson Senior Atmospheric Scientist UAH We Really Do Have The Most Advanced TV Radar! AMS San Antonio 2007

ARMOR: Advanced Radar for Meteorological and Operational Research. Location : Huntsville Intl. Airport Altitude (antenna MSL): 194 m Transmit frequency: 5625 MHz (C Band) Peak Power: 350 kW Pulse width:0.8  s Maximum PRF:1000 s -1 Antenna Diameter3.7 m (12 ft CF Parabolic) Antenna Beam width: 1.0 o First side-lobe:-23 to -24 dB Maximum rotation rate: 6 rpm Transmit polarization: Simultaneous H and V, or H Receive polarization: SIGMET dual-channel; H and V Signal Process:SIGMET RVP/8 Variables:Z, V, W, ZDR,  DP, KDP,  hv, LDR Partners: UAH, NASA, NSSTC, WHNT-TV Deployed in Huntsville by the NWS in 1977 as a local warning radar (WSR-74C) then refurbished and upgraded to Doppler in Radar donated to UAH in 2002 and upgraded to dual-polarimetry using the SIGMET Antenna Mounted Receiver 11/04. Renamed: ARMOR.

A UNIQUE COLLABORATION OPERATIONS

9/23/04 WSR-74C disassembly 10/29-11/05 ARMOR Reassembly

The Science behind ARMOR Many of these slide courtesy of Dr. Walt Peterson Senior Atmospheric Scientist University of Alabama Huntsville

Conventional Radar (NEXRAD) Polarimetric Radar (ARMOR) POLARIMETRIC RADAR? Courtesy NSSL

The Basics: By looking at the difference between Hor. Polarized Z and Vert. polarized Z we can determine size and shape of hydrometeors

Is it really that simple??

Don’t I wish it were! But… Unfortunately, it isn’t!

Remember when you learned storm relative velocity..VIL…ETC?

Well get ready for some new terms like Differential Reflectivity Linear Depolarization Ratio

Polarimetric Variables 1.Reflectivity factor Z at horizontal polarization - Measure of size and concentration of scatters (dominated by SIZE) 2.Differential reflectivity Z DR - Measure of median drop diameter → SIZE/SHAPE - Useful for rain / hail / snow discrimination → SIZE/SHAPE/PHASE 3.Differential phase Φ DP (Specific Differential Phase- K DP ) - Efficient for accurate rainfall estimation → NUMBER/SHAPE - Immune to radar miscalibration, attenuation, and partial beam blockage 4.Cross-correlation coefficient ρ hv - Indicator of mixed precipitation → SHAPE/PHASE - Efficient for identifying nonmeteorological scatterers Research: NCAR, CSU, NASA, UND, DLR, BMRC, NOAA-ETL ARMOR Operational: NEXRAD, TV vs Small ZDR Large ZDR

More accurate rainfall estimation (10-20% max accumulation error as opposed to %). Why? Because we collect information on drop size/shape/concentration and are able to mitigate hail contamination. (Kdp most useful!) Identification of precipitation types and discrimination between meteorological and non-meteorological scatterers Improvement in radar data quality: Calibration is more consistent using using polarimetric variables Advantages of Dual-Polarization Radar vs Small ZDR Large ZDR Small drops Large drops vs Hail Rain vs Insects Rain Mitigates the multiple Z-R issues! Estimating rainfall by assuming a standard drop size works, but rather poorly!

Spherical shape and tumbling of hail results in low ZDR’s (a ZDR “hole”). Large drop recirculation on edge of echo vault at x=25 km, z=2-3 km. Drop column clearly extends into sub-freezing portion of cloud- the hail process ZDR in Range-Height mode …………..(ARMOR has this scanning capability and this mode provides an early look into the development of intense storms) “ZDR Column” in developing convection “ZDR Hole” in Hail

61+ dBZ in cells: Hail or Rain? ARMOR: 1541 UTC 12/09/04 ZDR >3.5 dB ZDR: Big rain drops or melting hail

Squall Line on ARMOR from IRIS display

Squall Line on ARMOR from IRIS display (velocity)

The Television Side- Explaining all this to our viewers!

ARMOR Operates Like No Other TV Radar The radar alternates between a traditional Doppler mode and a multi-elevation polarimetric scan. This flexibility means more data into our office. Traditional radar measurements (reflectivity and velocity) are available at all times. Traditional radar measurements (reflectivity and velocity) are available at all times. Radar alternates its operation between a live.5 o surveillance scan and a 3 elevation volumetric scan at.7 o,1.3 o, and 2.0 o. Other volume scans and sector scans are easily tasked to the radar. Radar alternates its operation between a live.5 o surveillance scan and a 3 elevation volumetric scan at.7 o,1.3 o, and 2.0 o. Other volume scans and sector scans are easily tasked to the radar. Following each volume scan, a hydrometeor identification algorithm produces a product. Following each volume scan, a hydrometeor identification algorithm produces a product.

ARMOR in WHNT WX Office Sigmet IRIS Workstation FasTrac VIPIR

ARMOR and KHTX Side-by-Side Comparison December 10, 2004

December 10, 2004 Hail Event 61 dBZ with VIL ~30 kg/m 2

dBZ ZDR ARMOR: 12/10/04 17:55:06 EL=1.3 o Rain 55+ dBZ Hail 55+ dBZ Rain 2 to 3.5 dB Hail -1 to 0.5 dB Hail -1.5 to 0.5 dB Rain/Hail -0.5 to 2 dB Rain/Hail dBZ Hail dBZ

Ground-truth Report of Dime-Size Hail Owens Crossroads, Alabama.

The Good We have the only one in TV (For a few more hours!!)

The Good We have the only one in TV (For a few more hours!!) Hydro Meteor ID Really Works! (Limited evaluations so far.)

The Good We have the only one in TV (For a few more hours!!) Hydro Meteor ID Really Works! RVP8 Processor is Big Improvement

The Good We have the only one in TV (For a few more hours!!) Hydro Meteor ID Really Works! RVP8 Processor is Big Improvement Future Products Look Very Promising (3d Hydro ID in real time?)

The Bad How do you explain it to viewers? (I am open to suggestions!) Difficult to interpret in real time. (Algorithims are the key) Not a turn key system.. Graphics are made for science not TV.

Advantages of Dual Polarization Improved Hail Detection (fewer false alarms) Hydrometeor Identification works well! (an improved algorithm now available.) Possible Tornado Debris Detection to Improve Warnings (close to radar) Greatly Improved Rainfall estimates. Summary

Internet Sites with info on Dual Polarization Radar On NSSL Web Site-by Alexander Ryzhkov Excellent site by Kevin Scharfenberg at

Armor is on the Web! (Including Hydro. ID)