L. Tian et Rc. Srivastava, MEASUREMENT OF ATTENUATION AT C-BAND IN A CONVECTIVE STORM BY A DUAL-RADAR METHOD, Journal of atmospheric and oceanic technology, 14(1), 1997, pp. 184-196
Retrievals' of specific attenuation at 5.5-cm wavelength from dual-rad
ar observations of a summer convective storm in Florida are presented.
The retrieved specific attenuation is positive except in regions near
the radars where the observed reflectivity factors suffered from cont
amination by ground clutter. The specific attenuations ranged between
0.0 and 2.0 dB km(-1); they are small at higher levels of the storm, a
nd high reflectivity cores are generally associated with higher specif
ic attenuations. A plot of the retrieved specific attenuation against
reflectivity factor at 10-cm wavelength shows that a majority of the r
etrieved values agree with those calculated from empirical relationshi
ps between reflectivity factor and specific attenuation. A small fract
ion of the points having high reflectivity factors have smaller than e
mpirically predicted attenuations; these are attributed to dry ice par
ticles. A larger fraction of the points having low reflectivity factor
s, less than about 30 dBZ, have higher than empirically predicted atte
nuations; these are attributed to attenuation by cloud liquid water an
d mixed-phase hydrometeors. A scatterplot of the differential reflecti
vity factor at 10-cm wavelength against the ratio of the retrieved spe
cific attenuation to the reflectivity factor at 10-cm wavelength agree
s generally with a theoretically expected relationship between the two
parameters for horizontally oriented deformed raindrops, giving crede
nce to the retrievals. However, the points scatter rather widely aroun
d the theoretical curve and the scatter is attributed to 1) signal flu
ctuations; 2) physical factors, namely, cloud water, ice particles, an
d mixed-phase particles of various shapes; 3) instrumental factors, na
mely, ground clutter, finite pulse volume, mismatched radar antenna pa
tterns, and sidelobes; and 4) numerical procedures used in the retriev
als, namely, data interpolation, smoothing, and differentiation.