James-Paul Dice, Meteorologist WHNT-TV, Huntsville Dr. Walt Petersen, Scientist, University of Alabama Huntsville

ARMOR: Advanced Radar for Meteorological and Operational Research. Location : Huntsville Intl. Airport Transmit frequency: 5625 MHz Peak Power: 350 kW Antenna Diameter3.7 m (12 ft CF Parabolic) Antenna Beam width: 1.0 o 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

Digital dual-receiver Simultaneous transmit and receive via 4-port switch and magic-T Waveguide Assembly Receiver

The Science Behind ARMOR

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

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. Identification of precipitation types and discrimination between meteorological and non-meteorological scatterers Improvement in radar data quality: Self consistent way to calibrate using polarimetric variables Advantages of a Dual-Polarization Radar Really just a self-consistent way of obtaining a more complete description of the particle types and shapes present in a given volume of space. vs Small ZDR Large ZDR Small drops Large drops vs Hail Rain vs Insects Rain Mitigates the multiple Z-R issues!

How Does Dual Polarimetric Radar Help Hydrology? RAINFALL: A CLASSIC EXAMPLE The Fort Collins Flash Flood: A Robust Integrated Application of Dual-Polarization Radar CSU-CHILL: 2145 L 2108: RHI: dBZ, ZDR, KDP Review Petersen et al., BAMS, 1999

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

Winter: Rain-Snow lines- Application for ARMOR along AL-TN border ZDR ZeZe CSU CHILL White line indicates a transition from snow to rain- e.g., melting. This process is amplified in the ZDR signal and not as apparent in the reflectivity (Z).

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

ARMOR Dual-Polarimetric facility provides a unique opportunity for end- to-end transfer of research technology to public safety Flooding (Radar “state of the art” rainfall estimates and flexible scanning) Emergency Management Surveillance, threat detection, warning Mitigation Case study and climatological area- accurate rainfall boundary conditions (0.125 x 0.5 km) for modeled watershed response (improved flood plain planning) Severe Thunderstorms Additional local source for improving detection, monitoring of severe weather (tornadic, strong winds, hail, lightning) Winter Precipitation Rain-snow boundary (HSV Airport Authority very interested in this product); planning decision support Homeland Security Boundary layer winds for plume dispersion modeling- feasibility?

On-the-Air with ARMOR

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.05 o surveillance scan and a 3 elevation volumetric scan at.07 o,1.3 o, and 2.0 o Radar alternates its operation between a live.05 o surveillance scan and a 3 elevation volumetric scan at.07 o,1.3 o, and 2.0 o Following each volume scan, a hydrometeor identification algorithm produces a product. Following each volume scan, a hydrometeor identification algorithm produces a product.

Hydrometeor ID Algorithm Output

Large Hail Large Hail

Hydrometeor ID Algorithm Output Large Hail Large Hail

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

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

KHTX NEXRAD View of Storm Note: Pink Baron Services Severe SCIT. Neither NEXRAD or Baron Hail algorithm detected presence of hail during this event.

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 At 17:55 In-cloud (IC) flash rate ~ 3/minute in southern cell No IC’s in northern cell at 17:55 No Cloud-to-Ground (CG) lightning in either cell for 20 minutes centered on 17:55 Only 3 CG’s detected for duration of storms LMA S. Cell 17:52:30 – 17:57:30 LMA Total Lightning Data (southern cell mass)

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

ARMOR Control and Display

Sigmet IRIS Workstation FasTrac VIPIR

This is the Next Generation of Doppler Improved Flash Flood Forecasting Hydrometeor Identification Possible Tornado Debris Detection to Improve Warnings The Bottom Line: More data is a competitive advantage