On the Probability Density Distribution of Planetary-Scale Atmospheric Wave Amplitude

Abstract

The statistical properties of a measure of planetary-scale wave activity are investigated in a 16 winter NMC dataset. The probability density distribution of the wavenumber 2 to 4 amplitude is found to be bimodal, confirming earlier results from a smaller dataset. The statistical significance of this result is established empirically with statistical simulations. It is also shown that the bimodality is not connected with any periodicity in the time series. Partitioning the data based on the density estimation reveals two statistical flow regimes in physical space. One corresponds to an amplified planetary-scale wave pattern and the other to a predominantly zonal flow. Both regimes exhibit a baroclinic vertical structure but the difference between them is equivalent barotropic. These differences extend through the depth of the troposphere and appear to be of hemispheric extent.