Radar signal spectra dependence on the pulse width : observations using ST mode of the Indian MST radar

Abstract

Sensitive VHF Doppler radars are used to study the atmospheric turbulence characteristics and the atmospheric wind field. The three low-order moments of the spectrum of radar echoes correspond to the received signal power, mean Doppler shift and spectral width, respectively. The spectral width yields directly the rms deviation of the wind velocity from the mean. The spectral width is, therefore, directly related to the kinetic energy of the turbulence and hence it can be used to estimate the atmospheric turbulence parameters. However, in addition to the rms velocity deviation, wind shear and beam broadening also contribute significantly to to the broadening. The shear broadening and beam broadening effects are expected to depend on spatial resolution also, which is in turn a function of transmitted pulse length and the beam width. The observed spectral width needs to be corrected for these additional factors. The Indian MST radar has been used to study the dependence of spectral width on the length of the transmitted radio pulse.