Monday, 14 January 2002
Interaction of high- and low-frequency oscillations from a tropical cyclogenesis perspective
Although a great deal of study has been carried out with regard to low frequency, long-term oscillations in the tropics, there remain numerous unanswered questions regarding higher frequency, short-term oscillations. In particular the effects of high frequency intra-annual oscillations on regional and global tropical cyclogenesis have begun only recently to be examined in detail. A connection between low frequency oscillations such as the El Niņo/Southern Oscillation and higher frequency inter-basin oscillations is thought to exist in the tropics. Here, various characteristics of tropical cyclogenesis in the East Pacific and Atlantic basins are examined. Seasonal spatial and temporal positions of tropical cyclone genesis between 1950-2000 are recorded in both basins in a region confined from 10-35° N and 15-140° W. The genesis positions are then separated into two datasets based on origin as either an East Pacific or Atlantic system. Power spectra reveal the seasonal genesis frequencies for each region, and a subsequent lagged cross correlation yields a period of genesis oscillation between the two basins. This oscillation period is then compared to the average index value of ENSO to determine what-if any-effects the state of ENSO has on genesis oscillation. While the effect of ENSO on individual basin activity is well documented, this ENSO based inter-basin periodicity represents potential cyclogenesis oscillations in both the Atlantic and East Pacific basins on annual timescales.