ON THE PROBABILITY DENSITY DISTRIBUTION OF PLANETARY-SCALE ATMOSPHERIC WAVE AMPLITUDE

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. Partitioning the data based on the density estimation reveals 2 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 exten