Dynamical Activity Index

Planetary waves are the main drivers of the large-scale weather patterns of the mid-latitudes. The breaking of planetary waves leads to large-scale tongue-like structures (streamer events) and cut-off of air masses, such as high- or low-pressure cells in the mid-latitudes. Poleward breaking planetary waves lead airmasses into the higher latitudes. In order to study breaking planetary waves, the so-called Dynamical Activity Index, DAI is derived.

The DAI represents the planetary wave amplitudes based on AEOLUS horizontal wind measurements. The calculation of the DAI is based on a spectral analysis. We used a well-etablished least–square approach, called harmonic analysis which is described in detail in Bittner et al. (1994, 2000). With this we can decompose the dynamics into six harmonic wave modes, we call PW1 to PW6. The PW1 represents a planetary wave with a zonal wavelength of 360°, which means one maximum and one minimum along the longitudes. For the details of the calculation of the DAI see the official project report. For the DAI shown in the plots below we use hlos Rayleigh wind data of the data version L11 which covers data from June 2019 until May 2021.

You can zoom into the data, if you use the slider below the date. If you move the mouse over the data curve, you can view the values and times of the data point in the upper right corner.