The Dual-Wavelength Method for Hailstorm Detection by Airborne Radar

摘要

This paper focuses on a dual-wavelength technique to detect hail in convective cells from a weather airborne radar. The topic is of great interest since hailstorm is the main meteorological hazard in the context of civil aviation. Considering $S$, $C$, and $X$ frequency bands, the question of the most efficient frequency couple is addressed by means of simulations of airborne radar observations. A convective system made of two successive rows of convective towers is first modeled. Another one extracted from a real hailstorm is then considered. It is shown that the quantity $dy/dr$, where $r$ is the radial coordinate along the ray path and $y$ is the measured differential reflectivity at two different wavelengths, is a good indicator of hail areas. This quantity, associated with the measured reflectivity at the less attenuated wavelength (i.e., the longest one), enables one to identify convective cells containing hail. It appears that the frequency couples $S{-}X$ and $C{-}X$ are the best ones for hail detection. In the context of civil aviation, the second one $(C{-}X)$ permits one to minimize antenna size.