Optimizing the Radar Detection of Clear Air Turbulence

A general analysis is made of the turbulent refractivity spectrum in and beyond the limiting microscale and a relation derived for its scattering reflectivity in either the back or bistatic directions. Radar reflectivity is computed as a function of wavelength for regions of CAT. The results are compared to the minimum detectable reflectivity of airborne radars having optimum state of the art characteristics at each wavelength. It is shown that the best radars now feasible can barely detect the most reflective CAT at 10 n mi (i.e., 1 minute warning). A 20-db improvement in sensitivity is required for detection of most CAT, which appears to be just attainable by pre-detection integration. The optimum wavelength to implement is 5–6 cm. The best radar at this wavelength will also detect circus clouds reliably. Whether detecting clouds or chaff a measure of the echo fluctuation (or Doppler) spectrum is required to identify the intensity of CAT. However, in the case of high altitude clear air echoes, ...