Insects and Birds as Primary Contributors to Clear-Air Echoes at Centimeter Wavelengths: Evidence from Turbulence and Structure Constant

Clear-air echoes at centimeter wavelengths are predominantly attributed to insects and birds due to two factors: isotropic turbulence and the atmospheric structure constant. Kolmogorov's theory indicates that turbulence is homogeneous and isotropic, resulting in consistent scattering intensity of turbulence in both horizontal and vertical planes. Consequently, if the echo were caused by turbulence, then the turbulence differential reflectivity value (Z_DR) would equate to zero. Conversely, the clear-air echo's calculated atmospheric structure constant (C_n^2) is higher than observed values at the upper range.