Effects of Melting Layer in Airborne Meteorological X-Band Radar Observations

Most civil aviation aircraft are equipped with meteorological radar working at the X-band (f approximate to 10 GHz; lambda approximate to 3.2 cm). These radars use a small antenna and, thus, a large beamwidth, around 3 degrees-4 degrees, for observations over long distances (up to 350 km). In the presence of microphysical inhomogeneities inside a radar sampling volume, as filling by different hydrometeor categories, radar reflectivity measurements are biased. An important bias occurs when a radar cell is cut by a nonresolved layer of melting snowflakes whose attenuation is high compared to those of rain and dry snow. This paper illustrates the effects in precipitation-attenuation correction schemes (PACS) of the inhomogeneity associated with the 0 degrees C isotherm. It proposes a method to take into account these effects in PACS. Adaptation of the method to other frequency bands and ground-based radar observations is easy.