Differential Reflectivity

• Raindrops are not always spherical when they fall - especially the larger drops
• They tend to become more oblate -->>
• So, the reflectivity would be larger if the wave were horizontally polarized, or Z_h > Z_v
• Define Z_DR = differential reflectivity = 10 log (Z_h/Z_v)
• Z_DR is great for discriminating large drops from hail - hail tumbles randomly, looks like a spherical particle.
• Here are typical Z_DR values for different sized rain drops
• So, Z_DR for hail is about 0.
• Z_DR for ice is about 0 as well.

Z_DR example for a summertime thunderstorm:

• Reflectivity
• Z_DR
• Velocities

 Combining ZDR and other multi-parameter variables with dBZe can tell us much about the internal microphysical structure of storms

REQUIRED MATERIAL:

4. Dual-Pol Radar Products at:

http://www.wdtb.noaa.gov/courses/dualpol/index.html

image from NSSL