Daytime lidar measurements of tidal winds in the mesospheric sodium layer at Urbana, Illinois

Abstract

The first daytime lidar observations of the mesospheric Na layer at Urbana, Illinois (40°N, 88°W), were made in January and March 1986. The data show strong 12‐hour oscillations of the Na density and layer centroid height which appear to be caused by the semidiurnal tide. The peak‐to‐peak variations in column abundance and centroid height were of the order of 100% and 3 km, respectively. The vertical wind velocities were inferred from the temporal variations of the density gradients on the layer topside. The inferred wind amplitudes and vertical wavelengths for the semidiurnal tide were ∼30 cm s −1 and ∼50 km, respectively. The maximum upward vertical velocity occurs at about 1100 LST and 2300 LST.