GRLevel3 2.00 Radar Products

 

GRLevel3 displays all of the significant Level III radar products for both legacy and Dual Pol NEXRADs and TDWRs. Due to the mix of legacy, high resolution, and Dual Pol data streams, GRLevel3 works with categories of products. There are 14 categories:

BR Base Reflectivity Reflectivity is one of the fundamental radar products
BV Base Velocity Base Velocity is a fundamental Doppler radar product
SRV Storm Relative Velocity Base Velocity with the storm motion removed
SW Spectrum Width The amount of variability in the base velocity
ET Echo Tops Height of the 18 dbz reflectivity
VIL Vertically Integrated Liquid Estimate of liquid in a vertical column of reflectivity
OHP One Hour Precipitation Estimate of how much rain has fallen in one hour
STP Storm Total Precipitation Estimate of how much rain has fallen in an entire event
ZDR Differential Reflectivity Dual Pol product comparing the horizontal and vertical reflectivity
CC Correlation Coefficient Dual Pol product measuring the variability of echoes
KDP Specific Differential Phase Dual Pol product measuring liquid content in echoes
HCA Hydrometeor Classification Algorithm Dual Pol product estimating the type of echoes
DOD One Hour Difference Dual Pol product showing the difference between Dual Pol and legacy algorithms for One Hour Precipitation
DSD Storm Total Difference Dual Pol product showing the difference between Dual Pol and legacy algorithms for Storm Total Precipitation

 

The Dual Pol products are only available on NEXRADs that have been modified to support Dual Polarization.

GRLevel3 always chooses the highest quality product from each category. For example, on a Dual Pol NEXRAD, GRLevel3 displays the Dual Pol version of Storm Total Precipitation instead of the legacy product. Here are the radar products for each category (columns are: AWIPS, resolution, levels, range, name):

 

Base Reflectivity (BR):

NxQ 1° x 1000 m 256 460 km  Digital Base Reflectivity (up to 6 tilts)
NxR 1° x 1000 m 16 230 km  Legacy Resolution Base Reflectivity (4 tilts available)
NxZ 1° x 2000 m 16 460 km  Base Reflectivity 248nm
NCR 1° x 1000 m 16 230 km  Composite Reflectivity
NCZ 1° x 4000 m 16 460 km  Composite Reflectivity 248 nm
TRx 1° x 150 m 256 88 km  TDWR Base Reflectivity
TZL 1° x 300 m 256 415 km  TDWR Base Reflectivity 223 nm

 

Base Velocity (BV):

NxU 1° x 250 m 256 300 km  Digital Base Velocity (up to 6 tilts)
NxV 1° x 1000 m 16 230 km  Legacy Base Velocity (4 tilts)
TVx 1° x 150 m 256 88 km  TDWR Base Velocity

 

Storm Relative Velocity (SRV):

XxS 1° x 250 m 256 300 km  Digital Storm Relative Velocity (GRLevel3-derived)
NxS 1° x 1000 m 16 230 km  Legacy Resolution Storm Relative Velocity

 

Echo Tops (ET):

EET 1° x 1000 m 256 345 km  High Resolution Digital Echo Tops
NET 4 km x 4 km 16 230 km  Legacy Echo Tops

 

Vertically Integrated Liquid (VIL):

DVL 1° x 1000 m 256 460 km  High Resolution Digital VIL
NVL 4 km x 4 km 16 230 km  Legacy VIL

 

One Hour Precipitation (OHP):

DAA 1° x 250 m 256 230 km  Dual Pol One Hour Rainfall
OHR 1° x 2000 m 16 230 km  Legacy One Hour Rainfall

 

Storm Total Precipitation (STP):

DTA 1° x 250 m 256 230 km  Dual Pol Storm Total Rainfall
DSP 1° x 2000 m 256 230 km  Digital Storm Total Rainfall
OHR 1° x 2000 m 16 230 km  Legacy One Hour Rainfall

 

Dual Pol-Only Products (ZDR, CC, KDP, HCA, DOD, DSD):

NxX 1° x 250 m 256 300 km  Digital ZDR
NxC 1° x 250 m 256 300 km  Digital CC
NxK 1° x 250 m 256 300 km  Digital KDP
NxH 1° x 250 m 256 300 km  Digital HCA
HHC 1° x 250 m 256 230 km  Digital Hybrid HCA
DOD 1° x 250 m 256 230 km  Digital DP One Hour Difference
DSD 1° x 250 m 256 230 km  Digital DP Storm Total Difference

 

Melting Layer

The Melting Layer (ML) radar product is a series of lines showing the position of the melting layer relative to the radar beam for a given tilt. The melting layer itself is determined by the radar using three methods:

  1. Automated detection of the melting layer signature in CC and BR (when possible)
  2. Environmental model data (RAP). The freezing level is the top and the bottom is assumed to be 500 m below
  3. Manual entry of the melting layer top and bottom

Since the radar beam increases in height with range, the melting layer lines typically form rings around the radar site. These rings are not typically perfect circles due to two factors:

  1. The melting layer heights can vary around the radar site
  2. The beam elevation angle varies with azimuth (typically at the start of a tilt)

GRLevel3 only shows a particular tilt of the melting layer when its corresponding graphical radar product is displayed. For example, ML 0.5° only shows up on BR/BV/SRV 0.5°. There are up to four ML lines shown:

Inner Light Gray Ring  Where the beam top enters the Melting Layer
Inner Solid White Ring  Where the beam center enters the Melting Layer
Outer Solid White Ring  Where the beam center leaves the Melting Layer
Outer Light Gray Ring  Where the beam bottom leaves the Melting Layer

In winter you will sometimes only see the outer ML rings and/or partial ML rings because the bottom of the melting layer is below the radar site itself.