Statistics of gravity wave spectra in the troposphere and lower stratosphere over Beijing

Abstract

We utilize the temperature profiles with a height resolution of 50-m obtained over the Beijing Observatory in the period between January of 2002 and December of 2002 to study vertical wavenumber spectra of normalized temperature fluctuations in the 1.67–8.02 km and 13.57–19.92 km altitude ranges and compare them with linear saturation model. Results indicate that individual vertical wavenumber spectra reveal a considerable variability in both slope and amplitude. The observed variability is not consistent with the predictions of linear saturation model. However, mean vertical wavenumber spectra in the troposphere measured at different seasons and different local times show great similarities with fairly uniform negative slopes of ~3.0 and amplitudes proportional to N 4 , suggesting that the seasonal mean spectra observed in the troposphere completely obey the linear saturation model and are unique at present. In contrast, while the spectral slopes of the mean vertical wavenumber spectra in the lower stratosphere tend to support the explanation of the observed temperature fluctuations by linear saturation model, the spectral amplitudes diverge significantly from linear saturation model, suggesting that the seasonal mean spectra in the lower stratosphere do not obey the linear saturation model and are unique at present. The dominant vertical wavelengths derived from the observed mean vertical wavenumber spectra are estimated to be ~3.2–~2.1 km in the troposphere and lower stratosphere, which is generally consistent with those reported in the literature. Balloon measurements, temperature and temperature spectra, gravity waves and saturation mode, dominant vertical wavelengths.