The use of primary radar with a wavelength of 9 mm.
Airborne Weather Radar (AWR) is a primary radar system that is fitted to an aeroplane. The selected frequency for AWR is in the SHF band and is 9.375 GHz. This has an associated wavelength of 3.2 cm. AWR must be optimised not to detect very small particles such as thin fog but to accurately identify rain particles in storms.
Too small wavelengths will result in reflection from very small particles. Larger wavelengths result in the waves bending around particles of interest.
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