The Relative Roles of the Ocean and Atmosphere as Revealed by Buoy Air–Sea Observations in Hurricanes

Abstract

esults from this multihurricane study suggest that the criticality of the oft-cited 26°C hurricane threshold linked to hurricane maintenance may be more closely associated with atmospheric thermodynamic conditions within the inner core than previously believed. In all cases, a positive sea?air contrast was observed within the storm inner core (i.e., surface ocean temperature greater than surface air temperature), despite the fact that 6% of the hurricanes exhibited sea surface temperatures (SSTs) less than the 26°C. For the storms sampled in this study, inner-core surface dewpoint temperatures never exceeded 26.5°C. This finding may provide an alternate explanation as to the criticality of the 26°C threshold since SSTs above 26°C would, in almost all instances, be associated with a positive enthalpy flux condition. Analyses from this study also illustrate that high wind SSTs fluctuate as a function of storm latitude, while inner-core near-surface dewpoint temperatures are much less sensitive to this parameter. As a result, and assuming all other factors to be equal, low-latitude hurricanes would, on average, be expected to experience surface moisture fluxes ~1/3 greater than storms located farther to the north. For systems sampled within the deep tropics, inner-core SST was found to fluctuate much less than surface dewpoint temperature, suggesting that the atmosphere, not the ocean, is more likely to influence the key thermodynamic parameter controlling surface moisture flux for this subset of hurricanes.