Dual-Phase Warming of the Cold Wake of Typhoon Fanapi, 2010

Tens of thousands of temperature profiles were taken in and around the cold wake of category 3 Typhoon Fanapi between September and November 2010 as part of the Impact of Typhoons on the Ocean in the Pacific (ITOP) research program. This unprecedented data set presents outstanding opportunities for model verification as well as comparisons with remote sensing products. Fanapi's SST cold wake took under two weeks to disappear, however a subsurface cold wake signature was observed to persist for more than three weeks. Fanapi was a late-season typhoon, therefore the ocean affected by the cold wake never fully recovered to the pre-storm thermal structure. The cold wake warmed in two distinct phases; a rapid warming phase where the wake was capped by a shallow, warm mixed layer in 4-5 days, followed by a slower warming phase that gradually brought the cold wake to equilibrium with the surrounding ocean. One dimensional air-sea interaction modeling reveals that preferential warming took place over the cold wake, forming the warm cap, thereby isolating the subsurface cold wake from the atmosphere. After this, the warm cap slowly deepened and warmed as it interacted with the subsurface cold wake layer below and the atmosphere above.