Spectral estimation of wave-driven fluctuations in Rayleigh lidar temperature measurements

Abstract

The NICT-Rayleigh lidar has been operated at Chatanika, Alaska (65°N, l47°W) since November 1997. These lidar observations have yielded temperature and density measurements in the stratosphere and mesosphere (̃40-80 km). The goal of this thesis is to estimate the signal and noise power in the relative temperature perturbations. The uncertainties in these estimates due to instrumental variability and geophysical variability are also determined. This analysis quantifies the relative contributions of gravity waves and instrumental noise to the total power measured by the lidar. Eighty-nine nights of observations have yielded 80 sets of data that are of sufficient quality to study the gravity-wave activity at 30-minute resolution in the 40-50 km altitude region. The rms temperature and density perturbations from early August to mid-May are found to be statistically identical. The rms temperature fluctuations are found to have an average value of 0.44% with a maximum value of 1.28% on March 12th 2004 and a minimum value of 0.20% on September 16th 2003. These rms amplitudes are similar to values reported from other Arctic sites.