We tend to place a great deal of emphasis on severe
weather detection. However, reflectivity serves many
other practical uses on a daily basis. For example, we
know that precipitation produces a minimum of 18.0
dBZ reflectivity return. Therefore, returns of less than
18.0 dBZ might be attributed to nonprecipitable cloud
droplets or other minute scatterers. From this we can
estimate cloud heights (bases, tops), the thickness of
cloud layers, and the height of the freezing level
(altitude at which the air temperature equals 0°C).
In addition, reflectivity can also be used to locate
the melting level. The melting level is very close to and
just below the freezing level; therefore, the melting
level is slightly warmer. As frozen particles descend
through the melting level, they become lightly coated
Figure 2-34 .—Thunderstorm cell exhibiting (A) Weak Echo Region (WER), (B) Bounded Weak Echo Region (BWER).
with water. This makes them highly reflective and
produces returns that are stronger than either the frozen
particles above or the liquid droplets below. When
stratiform clouds are present, the melting level appears
as a halo around the RDA (referred to as the bright
band).
Keep in mind that the presence of either ground
clutter, anomalous propagation, or hail can
significantly contaminate reflectivity data and all
products built from such data. The Base Reflectivity
product may be severely biased, resulting in
exaggerated intensities. The product can become
deceiving, indicating the presence of strong storms,
which may or may not be real. Range folded areas can
also cause misinterpretation or obscure valuable data
2-37
