So far, different parameters e.g. Reflectivity, signal to noise ratio, power etc have been used to study PMSE echoes. Could any one suggest me the more useful parameter out of these three or any other they know ?
Depends what one plans to do with the PMSE data. For example, if goal is to investigate the wave activity in the summer mesopause region, probably Doppler velocity is the best to use. If one plans to do a statistical analysis about the phenomena itself, I do not expect big difference using SNR or volume reflectivity. Spectral width is used sometimes to highlight the turbulent areas in the observed region.
So, important is to define the interest of research whether assume PMSE as a tracer and use it to study dynamical processes or obtain background wind, or purpose is to investigate the PMSE morphology, micro-physics etc.