Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes

摘要

The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic waveperiod, horizontal wave length and projection mean wind along the horizontalwave vector. Their projection phase and groupvelocities along the oblique radar beam (v_pr and v_gr), withdifferent zenith angle θ and azimuth angle φ, were analyzed bythe method of phase- and group-velocity tracing. The results wereconsistent with the theoretical calculations derived by the dispersionrelation, reconfirming the accuracy of the method of analysis. The RTI plotof the numerical wave packets were similar to the striation patterns of the QPechoes from the FAI irregularity region. We propose that the striation rangerate of the QP echo is equal to the radial phase velocity v_pr, and the slopeof the energy line across the neighboring striations is equal to the radialgroup velocity v_gr of the wave packet; the horizontal distance betweentwo neighboring striations is equal to the characteristic wave period τ.Then, one can inversely calculate all the properties of the gravity waveresponsible for the appearance of the QP echoes. We found that the possibilityof some QP echoes being generated by the gravity waves originated from loweraltitudes cannot be ruled out.