A method is developed to calculate nonlinear zonal, sx, and meridional, sy, longitudinal advective accelerations from MU radar observations with antenna beam scanning in eight directions. The results of measurements of sx and sy at altitudes of 2--18 km on April 16--18, 1997, are presented. The values of sx and sy are mainly between -0.01 m s-2 and 0.01 m s-2 with increases up to ¿0.04 m s-2 during tens of minutes to several hours in regions with vertical scales up to several kilometers. Such extremes are more frequent at the altitudes of tropo-stratospheric jet at 10--15 km and may indicate regions of inclination from geostrophic balance and of increased generation of atmospheric waves. ¿ 1999 American Geophysical Union