Climate control of the global tropical storm days (1965–2008)

The tropical storm days have a consistent global record over the past 44 years (1965–2008), which provides an alternative metric for integrated information about genesis, track, and lifespan. Seasonal-reliant singular value decomposition is performed on the fields of the global storm days and sea surface temperature by using the “best track” data. The leading mode, which dominates the variability of the global total number of storm days, displays an east-west contrast between enhanced activity in the North Pacific and reduced activity in the North Atlantic and a north-south contrast in the Southern Hemisphere oceans between active tropics and inactive subtropics, which are coupled with the El Niño and a positive phase of the Pacific Decadal Oscillation (PDO). The second mode reveals a compensating trend pattern coupled with global warming: upward trends over the North Atlantic and the Indo-Pacific warm pool (17.5°S–10°N, 70–140°E) and downward trends over the Pacific, especially the South Pacific. However, the global total number of storm days shows no trend and only an unexpected large amplitude fluctuation driven by El Niño-Southern Oscillation and PDO. The rising temperature of about 0.5°C in the tropics so far has not yet affected the global tropical storm days.