The climatology and characteristics of Rossby wave packets using a feature-based tracking technique

This paper describes an objective, track-based climatology of Rossby wave packets (RWPs). NCEP-NCAR reanalysis wind and geopotential height data at 300 hPa every 6 h were spectrally filtered using a Hilbert transform technique under the assumption that RWPs propagate along a waveguide defined by the 14-day running average of the 300-hPa wind. Track data and feature-based descriptive statistics, including area, average intensity, intensity volume (intensity multiplied by area), intensity-weighted centroid position, and velocity, were gathered to describe the interannual, annual, seasonal, and regime-based climatology of RWPs. RWPs have a more pronounced seasonal cycle in the Northern Hemisphere (NH) than the Southern Hemisphere (SH). RWPs are nearly nonexistent in the summer months (June-August; JJA) in the NH, while there is nearly continuous RWP activity downstream of South Africa during austral summer (December-February; DJF). Interannual variability inRWPfrequency and intensity in the Northern Hemisphere is found to be strongly connected with the large-scale flow regimes such as El Niño-Southern Oscillation and the Arctic Oscillation. Enhanced RWP activity is also found to coherently propagate from the Pacific into the Atlantic on average when the Arctic Oscillation switches from a positive to a negative phase. No significant long-term (30 yr) trend in RWP frequency, activity, or amplitude is found.