On the differences in determining the time and vertical velocity characteristic scales and analyzing high order derivatives suggested by certain authors, discussions are made and preliminary conclusions are drawn, namely,τ~L/U, W≤ MUH/L and  nf/x n～F/L n,n>1 for a single scale motion. Based upon them the orders of magnitude of several characteristic scales currently used for atmospheric motion are presented, and then compared with the statistical observations in mesoscale gravity wave and severe convection cases.