• Spectral estimation of signal and noise power in rayleigh lidar measurements of the middle atmosphere

      Wang, Weiyuan (2003-08)
      A Rayleigh lidar has been operated at Chatanika, Alaska (65°N, 147°W) since November 1997. The lidar observations yield temperature and density measurements in the stratosphere and mesosphere (40-80 km). This thesis presents a systematic engineering analysis of the retrieval methods used to determine both the temperature and density profiles as well as the density perturbations. Statistical and spectral analysis techniques are used to determine the total power in the density perturbations and estimate the power component due to geophysical variability and the power component due to instrumental noise. The power in the density perturbations is used to characterize the gravity-wave activity at this high-latitude site. Seventy-four nights of observation yielded 60 observation periods of data of sufficient quality to estimate the rms amplitude of the relative density perturbation in the 40-50 km altitude region at 30 min resolution. For these observations the average rms amplitude has a value of 0.43%. Preliminary investigation of campaign measurements in the spring of 2003 indicates that higher values of rms wave amplitude are associated with the presence of mesospheric inversion layers.