Review of Radar Measurements of Precipitation for the Characterization of Propagation Effects on Terrestrial and Slant Path Radio Links

Meteorological radars are unique instruments for the observation and measurement of precipitation, of which they can provide extensive information depending on the equipment characteristics. In particular, all radars provide reliable measurements over large areas (100 km in range and even more) and, at the same time, with high spatial detail (from some tenths of meters to some hundreds of meters). From ground-based conventional radars, such as the ones commonly used in radar networks [1], whose standard outputs are the average backscatter from meteorological targets (reflectivity) and the Doppler information (radial target speed component), it is possible to derive maps of precipitation routinely collected with a temporal detail of the order of 5 minutes or even less. Polarimetric radars, which operate by transmitting wave pulses in two orthogonal polarizations (usually Horizontal (H) and Vertical (V)), provide as output, other than the standard quantities, also specific information strictly related to the reflected H and V signals [2], [3]. All the outputs of meteorological radars are indirect measurements of the intensity, state and basic characteristics of precipitation. The accuracy of the measurements is of primary importance and most polarimetric data are quite complex to handle. This paper is intended to give a review of some unique contributions from ground-based and space-based radar data for propagation related studies and modeling.