318
P. Joe
Spahn JF, Smith PL Jr. (1976) Some charcteristics of hailstone size distributions inside
hailstorms, 17th Radar Met. Conf., 534-537
Torlachi E, Humphries RG, Barge BL (1984) Circular polarization for precipitation measurements. Radio Sci 19: 193-200
Tuttle JD, Rinehart RE (1983) Attenuation correction in dual-wavelength analysis. J Climate Appl Met 22: 1914-1921
Ulbrich CW (1983) Natural variations in the analytical form of the raindrop-size distribution.
J Clim Appl Met 22: 1764-1775
Ulbrich CW, Atlas D (1984) Assessment of the contribution of differential polarization to
improve rainfall measurement. Radio Science 19 (1): 49-57
van Gorp JJ (1995) To be or not to be a microburst, 27th Conference on Radar Met., Vail,
CO, Amer Met Soc
Wakasugi K, Mizutani A, Matsuo M, Fukao S, Kato S (1987) Further discussion on
deriving drop-size distribution and vertical air velocities directly from VHF Doppler radar
spectra. J Atmos Oceanic Technol 4: 170-179
Waldvogel A, Federer B, Grimm P (1979) Criteria for the detection of hail cells. J Appl
Met 18: 1521-1525
Wilson JW, Schreiber WE (1986) Initiation of convective storms at radar- observed
boundary-layer convergence lines. Man Wea Rev 114: 2516-2536
Wood VT, Brown RA (1986) Single Doppler velocity signature interpretation of nondivergent environmental winds. J Atmos and Oceanic Tech 3: 114-128
Zawadzki II (1975) On radar-raingauge comparison. Joum Applied Met 14: 909-928
12.10 Appendix A: Radar Terminology, Characteristics and Units
Tables 12.6-12.9 summarize the terminology, characteristics and units commonly used in weather radar.
The common weather radars use a magnetron transmitter and are called non-coherent, that is
the phase of each pulse is random. True Doppler radars use a Klystron transmitter where the
phase of every pulse is the same. The phase measurements are used to determine the radial
velocity of any target encountered. Magnetrons can also be used to measure velocities in noncoherent Dopplers and in this case electronics must be incorporated to save the phase of each
transmitted pulse to compare with the received pulse. Generally, due to the higher costs of
Klystron systems, the use of magnetron systems have been favored.
Spherical rain drops become elliptically shaped with the major axis in the horizontal plane
when falling freely in the atmosphere. The oblateness of the drop is related to the drop size.
The oblateness then becomes a measure of the diameter. The power backscattered from an
oblate spheroid is larger for a horizontally polarized wave than for the vertically polarized wave
provided the drops satisfy Rayleigh scattering. The difference is some measure of the oblateness
from which it is postulated, also a measure of the drop diameter. Using suitable assumptions
a drop size distribution can be derived and thus a rainfall rate.
The differential reflectance, called ZDR, is defined as ten times the logarithm of the ratio of the
horizontally polarized reflectance ZH, and the vertically polarized reflectance Zv. Comparisons
P. Joe
Spahn JF, Smith PL Jr. (1976) Some charcteristics of hailstone size distributions inside
hailstorms, 17th Radar Met. Conf., 534-537
Torlachi E, Humphries RG, Barge BL (1984) Circular polarization for precipitation measurements. Radio Sci 19: 193-200
Tuttle JD, Rinehart RE (1983) Attenuation correction in dual-wavelength analysis. J Climate Appl Met 22: 1914-1921
Ulbrich CW (1983) Natural variations in the analytical form of the raindrop-size distribution.
J Clim Appl Met 22: 1764-1775
Ulbrich CW, Atlas D (1984) Assessment of the contribution of differential polarization to
improve rainfall measurement. Radio Science 19 (1): 49-57
van Gorp JJ (1995) To be or not to be a microburst, 27th Conference on Radar Met., Vail,
CO, Amer Met Soc
Wakasugi K, Mizutani A, Matsuo M, Fukao S, Kato S (1987) Further discussion on
deriving drop-size distribution and vertical air velocities directly from VHF Doppler radar
spectra. J Atmos Oceanic Technol 4: 170-179
Waldvogel A, Federer B, Grimm P (1979) Criteria for the detection of hail cells. J Appl
Met 18: 1521-1525
Wilson JW, Schreiber WE (1986) Initiation of convective storms at radar- observed
boundary-layer convergence lines. Man Wea Rev 114: 2516-2536
Wood VT, Brown RA (1986) Single Doppler velocity signature interpretation of nondivergent environmental winds. J Atmos and Oceanic Tech 3: 114-128
Zawadzki II (1975) On radar-raingauge comparison. Joum Applied Met 14: 909-928
12.10 Appendix A: Radar Terminology, Characteristics and Units
Tables 12.6-12.9 summarize the terminology, characteristics and units commonly used in weather radar.
The common weather radars use a magnetron transmitter and are called non-coherent, that is
the phase of each pulse is random. True Doppler radars use a Klystron transmitter where the
phase of every pulse is the same. The phase measurements are used to determine the radial
velocity of any target encountered. Magnetrons can also be used to measure velocities in noncoherent Dopplers and in this case electronics must be incorporated to save the phase of each
transmitted pulse to compare with the received pulse. Generally, due to the higher costs of
Klystron systems, the use of magnetron systems have been favored.
Spherical rain drops become elliptically shaped with the major axis in the horizontal plane
when falling freely in the atmosphere. The oblateness of the drop is related to the drop size.
The oblateness then becomes a measure of the diameter. The power backscattered from an
oblate spheroid is larger for a horizontally polarized wave than for the vertically polarized wave
provided the drops satisfy Rayleigh scattering. The difference is some measure of the oblateness
from which it is postulated, also a measure of the drop diameter. Using suitable assumptions
a drop size distribution can be derived and thus a rainfall rate.
The differential reflectance, called ZDR, is defined as ten times the logarithm of the ratio of the
horizontally polarized reflectance ZH, and the vertically polarized reflectance Zv. Comparisons