Spatial and Temporal Variations of Gravity Wave Parameters. Part I: Intrinsic Frequency, Wavelength, and Vertical Propagation Direction

Abstract Five years (1998–2002) of U.S. high vertical resolution radiosonde data are analyzed to derive important gravity wave parameters, such as intrinsic frequencies, vertical and horizontal wavelengths, and vertical propagation directions in the lower stratosphere and troposphere. Intrinsic frequencies ω increase with increasing latitude, with larger values in the troposphere. In the lower stratosphere, ω is higher in winter than in summer, especially at mid- and high latitudes. Intrinsic frequencies divided by the Coriolis parameter f are ∼4 in the troposphere, and ∼2.4–3 in the lower stratosphere. The lower-stratospheric ω/f generally decreases weakly with increasing latitude. The latitudinal distributions of the lower-stratospheric ω/f are explained largely by the propagation effects. The seasonal variations of ω in the lower stratosphere are found to be related to the variations of the background wind speeds. Dominant vertical wavelengths decrease with increasing latitude in the lower stratos...