On the multi-decadal oscillation of Atlantic tropical storm activity

Abstract

Long term Atlantic tropical storm activity is described by the time series of the yearly Accumulated Cyclone Energy (ACE) Index for the time interval 1851-2007. ACE is a measure of total wind energy for North Atlantic basin and land falling tropical cyclone activity. Since the ACE index reflects a combination of storm intensity and duration it is a better measure of overall activity and likely damage than the number of either basin or land falling tropical storms or hurricanes. The yearly ACE time series is non-stationary, and one step toward detecting possible long-term quasi-periods is to detrend the original data. In this paper we use a procedure for data transformation by which ACE index is fitted in least square sense with polynomials of increasing order, followed by detrend. It is shown that, with some approximation, the obtained time series is cyclostationary, and a multi-decadal oscillation is detectable, as indicated by the power spectrum analysis.

Keywords

• time series
• quasi-periodicity
• trend
• non-stationarity