Note that these are averages of the derived parameters and not parameters derived from an average velocity spectrum. In the absence of any signal echo the main contribution to noise is the radio noise from our galaxy. Atmospheric absorption events reduce the level of noise. Receiver gain and cable attenuation fluctuations may have a small influence. Operator modification of gain controls are rare.
Strong signals can corrupt the computation through their sidelobes.
The errors given are the root mean square values of the deviation from the mean for that hour. There are 4 areas in the summary plots for neutral velocities for four 2-day periods between 0 and 80 km. When both eastward and northward velocities are available, there are vector plots for every 3 km where eastward is to the right and northward is upward. When horizontal vectors are unavailable, the vertical neutral velocity is plotted as line plots every 5 km. Hardy, K. R. and K. S. gage, The history of radar studies of the clear atmosphere, Chapter 17 of Radar in Meteorology, editor D. Atlas, Am.