A fresh look at ocean's part of necessary conditions in supertyphoon's intensification

Using more than 10,000 recently-available in situ upper ocean thermal structure profiles from the Argo autonomous floats, this work aims to give a fresh look at ocean's part of necessary conditions for the western North Pacific category-5 typhoons. Three parameters are studied, i.e., sea surface temperature, upper ocean heat content, and warm layer thickness (represented by the depth of the 26 degree C isotherm). It is found that to support suerptyphoon's intensification to category-5, sea surface temperature is typically above 28 degree C. However, the 2 subsurface-related parameters (i.e., upper ocean heat content and warm layer thickness) need to be considered with respect to storm's translation speed because the requirements for fast and slow-moving storms are different. It is found that faster-moving storms do not need as high the upper ocean heat content or as thick the warm layer, because the self-induced ocean cooling negative feedback is less pronounced under faster translation speeds. Using the Argo in situ profiles and an ocean mixed layer model, preliminary relationships between the 2 subsurface parameters and storm's translation speed are established. Typically, if a storm travels at 5m s-1, the required minimal warm layer thickness is around 80m and the upper ocean heat content is around 75 kj cm-2.