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The scale of dBZ values can be seen along the bottom of the image. dBZ is a logarithmic dimensionless technical unit used in radar. It is mostly used in weather radar, to compare the equivalent reflectivity factor (Z) of a remote object (in mm 6 per m 3) to the return of a droplet of rain with a diameter of 1 mm (1 mm 6 per m 3). [1]
Radar cross-section (RCS), denoted σ, also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected. [1] An object reflects a limited amount of radar energy back to the source. The factors that influence this include: [1] the material with which the target is made;
In the United States NEXRAD network some of these angles are .5, 1.45, 2.4, and 3.35 degrees with the radar having up to 14 angles when it is in Severe Mode. [ 1 ] [ 2 ] In the composite reflectivity product, the highest intensities among those available on the different angles above each point in the image will be displayed.
Optical cross section (OCS) is a value which describes the maximum amount of optical flux reflected back to the source. [1] The standard unit of measurement is m 2 /sr. OCS is dependent on the geometry and the reflectivity at a particular wavelength of an object.
Radar designers try to use the highest PRF possible commensurate with the other factors that constrain it, as described below. There are two other facets related to PRF that the designer must weigh very carefully; the beamwidth characteristics of the antenna, and the required periodicity with which the radar must sweep the field of view.
Backscattering is the principle behind radar systems. In weather radar, backscattering is proportional to the 6th power of the diameter of the target multiplied by its inherent reflective properties, provided the wavelength is larger than the particle diameter (Rayleigh scattering). Water is almost 4 times more reflective than ice but droplets ...
Reflective array 'billboard' antenna of the SCR-270 radar, an early US Army radar system. It consists of 32 horizontal half wave dipoles mounted in front of a 17 m (55 ft) high screen reflector. With an operating frequency of 106 MHz and a wavelength of 3 m (10 ft) this large antenna was required to generate a sufficiently narrow beamwidth to ...
where Q is the efficiency factor of scattering, which is defined as the ratio of the scattering cross-section and geometrical cross-section πa 2. The term p = 4πa( n − 1)/λ has as its physical meaning the phase delay of the wave passing through the centre of the sphere, where a is the sphere radius, n is the ratio of refractive indices ...