Composite Reflectivity - Warning Decision Training Division (WDTD)

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Composite Reflectivity

Short Description

The maximum reflectivity in a vertical column using the 3D Reflectivity Cube.

Subproducts

Low-Resolution (5 km) Composite Reflectivity

Composite Reflectivity (0–4 km)

Primary Users

NWS: WFO, CWSU, RFC, SPC, AWC

FAA: TRACON, ARTCC, ATCSCC

Other: EM

Input Sources

3D Reflectivity Cube

Resolution

Spatial Resolution: 0.01^o Latitude (~1.11 km) x 0.01^o Longitude (~1.01 km at 25^oN and 0.73 km at 49^oN)

Temporal Resolution: 2 minutes

Product Creation

At each horizontal 2D grid point, the reflectivity value is checked in the vertical grid from the bottom up. Once an “available” data value is found, that reflectivity value is assigned to the composite reflectivity value. As successively-higher altitude grid points are checked, if the reflectivity value is greater than the assigned composite reflectivity value, then the assigned value is replaced with the higher value of reflectivity. This process continues until the highest-altitude grid point is reached.

Technical Details

Latest Update for Low-Resolution (5 km) Composite Reflectivity: MRMS Version 11

Latest Update for Composite Reflectivity (0–4 km): MRMS Version 11.5

References

Lakshmanan, V., T. Smith, K. Hondl, G. J. Stumpf, and A. Witt, 2006: A real-time, three dimensional, rapidly updating, heterogeneous radar merger technique for reflectivity, velocity and derived products. Wea. Forecasting, 21, 802-823.

Lakshmanan, V., A. Fritz, T. Smith, K. Hondl, and G. J. Stumpf, 2007: An automated technique to quality control radar reflectivity data. J. Appl. Meteor., 46, 288-305.

Lakshmanan, V., C. Karstens, J. Krause, and L. Tang, 2014: Quality control of weather radar data using polarimetric variables. J. Atmos. Oceanic Tech., 31, 1234-1249.

Strengths

Like all MRMS products, the use of multiple radars is more robust than single-site radar alone. It provides faster updates and helps the forecaster integrate data from multiple radars. It also compensates for cone-of-silence, beam broadening at far ranges, and terrain blockage.

Low-Resolution Composite Reflectivity may help with latency/bandwidth issues.

Limitations

The height of the maximum reflectivity is not identified. You can refer to the “Composite Reflectivity Height” product for this information.

Bright band contamination is not removed.

Quality Control

This product is derived from the 3D Reflectivity Cube, which means non-hydrometeorological data has been removed including: Ground clutter, anomalous propagation (AP), chaff, interference spikes, and bioscatterers (e.g., angels and ghosts). However, bright band contamination (i.e., anomalously-high reflectivity caused by melting snowflakes) remains.

To see a version with non-meteorological echoes retained (to identify fronts, boundaries, etc.), refer to “Legacy Composite Reflectivity – UnQCed.”

Applications

As with single-radar composite reflectivity, this product is a good situational awareness tool to determine the first convective echo, as well as the overall extent of mature thunderstorm echoes (especially in the echo overhang region).

Example Images

Fig. 1: Composite Reflectivity for a MCS over North Dakota and Minnesota at 2204Z on 21 July 2014.