A Universal Hurricane Frequency Function

Evidence is provided that the global distribution of tropical hurricanes is principally determined by a universal function H of a single variable z that in turn is expressible in terms of the local sea surface temperature and latitude. The data-driven model presented here carries stark implications for the large increased numbers of hurricanes which it predicts for a warmer world. Moreover, the rise in recent decades in the numbers of hurricanes in the Atlantic, but not the Pacific basin, is shown to have a simple explanation in terms of the specific form of H(z), which yields larger percentage increases when a fixed increase in sea surface temperature occurs at higher latitudes and lower temperatures. 1. Introduction There are numerous factors that either promote or inhibit the formation of hurricanes or tropical storms, and it is well known that two of them have special significance: the sea surface temperature SST (or simply ) and the latitude at the time and place of storm formation. The importance of latitude is that it governs the strength of the Coriolis Effect, a principal factor in creating some initial vorticity, while the SST is the source of an updraft of air that can create a tropical low. Here, we assert more specifically that the probability density of a hurricane or tropical storm forming can be expressed in terms of a simple mathematical function of those two variables, . Alternatively, we can even write in terms of a single combined variable , where is the SST, is a threshold value of 25. C, and is the latitude. The functional form of most consistent with the data is found to be a simple power law, , where and , for most regions of the globe. This result appears to be independent of time and location, with the exception of those regional departures. The study reported here rests on four key assumptions. (a)Existence. There exists a probability function which describes whether a hurricane (also referred to as a cyclone or typhoon) forms. Furthermore, we assume that depends on numerous variables, of which only the SST and the latitude play a universal role, with the other “secondary” variables being restricted in time or space.(b)Secondary Variables. The secondary variables influencing do so in a way that simply multiplies it by a constant factor that is regionally and temporally limited and can be explained in terms of previously studied regional or oscillatory phenomena that enhance the value of by a specific factor over that spatial or temporal region.(c)Data Driven. The function can be found using the data on recorded hurricanes,