Description of the data
The dataset documents the variability in one of the major zonally asymmetric atmospheric circulation features in the Southern Hemisphere extratropics, the Zonal wave 3 pattern (ZW3; Raphael, 2004; Goyal et al., 2021). ZW3 explains ~40% of the variability in the monthly 500hPa meridional wind anomalies in the Southern Hemisphere extratropics. Time-series of monthly diagnostics are available for the period from 1979-present, specifically time series of the magnitude and phase of the ZW3 pattern are documented. The diagnostics are derived from the European Centre for Medium Range Weather Forecasts (ECMWF) ERA5 reanalysis (Hersbach et al., 2020){Hersbach, 2020 #17346}, which is an observationally-constrained reconstruction of atmospheric conditions. The index has been found to be useful for understanding the impact of ZW3 variability on the atmospheric meridional heat transport and Antarctic sea-ice concentration.
The ZW3 magnitude and phase indices were calculated following the definition detailed in Goyal et al., (2022). This is based on meridional wind at 500 hPa level (approximately 5km above mean sea level). EOFs of 500 hPa meridional wind anomalies were calculated between 40-70oS and the first two principal components were used to compute the magnitude and phase index for ZW3.
Acknowledgements
The European Centre for Medium Range Weather Forecasting is thanked for providing the ERA-Interim datasets.
