Comparative MF radar and Na lidar measurements of fluctuating winds in the mesopause region

Na lidar and MF radar observations of the mesopause region (≈ 80-105 km) were made over a 2-year period at Urbana, Illinois (40°N, 88°W). The Na lidar data yielded both temperature profiles and Na density profiles which are used to derive independent estimates of the rms horizontal winds. Estimates of the rms horizontal winds from concurrent radar and lidar measurements are obtained on 37 nights, totaling 263 hours. These three sets of rms wind estimates are processed in a common fashion. This analysis yields vertical profiles of the rms winds that do not grow exponentially with altitude, indicating that the gravity wave field is saturated throughout this altitude region. All three techniques reveal an annual maximum in the summer rms horizontal winds. However, the Na density estimates also have a semiannual variation with a second maximum in winter, which was not produced by the other techniques. Estimates of the rms winds derived from lidar Na density and Na temperature data are comparable in magnitude. The radar estimates are systematically larger than both sets of lidar estimates at higher altitudes. The discrepancy between the radar and lidar estimates is found to be greatest at those altitudes where the saturation is most pronounced.