radiates energy in the same microwave region of the
electromagnetic spectrum that is used by the WSR-
88D.
RECOGNITION OF SOLAR EFFECTS.— These
echoes may be expected to appear as continuous
returns, in a narrow “baseball bat” shape, out one or
two radials at the solar attitude. Reflectivity values
generally range between 10 and 20 dBZe. See figure
12-5. Solar effects will appear for one or two volume
scans at a single elevation of the Reflectivity, Mean
Radial Velocity, or Spectrum Width product and up to
30 min on a Composite Reflectivity product.
ASSESSING
IMPACTS
OF
SOLAR
EFFECTS.— In the absence of other echoes, typical
reflectivity values from solar effects are from near zero
dBZe in close to the radar, to 20 dBZe or higher at 250
nmi. The apparent reduction in the sun’s signal nearer
the radar is due to the range normalization correction
applied to reflectivity. The velocity and spectrum width
fields indicate range-aliased data out to the maximum
range of these products, that is, 124 nmi. Other
Reflectivity-derived products that will show this
contamination are the Echo Tops, Composite
Reflectivity, and Layer Composite Reflectivity. The
Storm Series algorithms will generally not be affected
since the reflectivity values are below the thresholds
used to detect storms.
Velocity-derived products that will be contaminated
are the Storm Relative Mean Radial Velocity Map, and
Region. At longer ranges, the contaminated radial may
disrupt pattern vectors used to identify circulations in
the mesocyclone algorithm, where the sun’s signal is
stronger than the corresponding storm echo. At close-in
ranges, the sun’s signal is too weak to impact the
Tornadic Vortex Signature algorithm.
The solar effects can also cause erroneous output
and increase edit time of the radar-coded message in
these areas.
INTERPRETATION OF DOPPLER
VELOCITY PATTERNS
Although a single doppler radar observes only the
component of the wind in a radial direction from the
Figure 12-5.-Streaks of low reflectivity extending outward for two radials to the northeast of the radar
caused by solar effects.
12-8
