JP3.35
Upper ocean thermal structure and the western North Pacific supertyphoons
I.-I. Lin, Dept. of Atmospheric Sciences, Taipei, Taiwan; and I. F. Pun and C. C. Wu
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 „aC isotherm). It is found that sea surface temperature is typically above 28 degree C. However, the 2 subsurface 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, relationships between how much the 2 subsurface parameters are required according to the translation speed are established. For example, if a storm transverses slowly (e.g., at 2 m s-1), the required minimal warm layer thickness is typically around 130m and the upper ocean heat content is around 120 kj cm-2. With increase in translation speed the requirements decrease. For example, at 7 m s-1 the requirement is only half that the required minimal warm layer thickness is typically around 60m while the required heat content is around 55kj cm-2.
Currently there is much discussion on the warming of the upper ocean heat content and its relation to climate change. In the future it would also be interesting to discuss this variability with respect to change in cyclone's translation speed.
Joint Poster Session 3, Tropical Cyclones and Climate Change Poster Session
Monday, 21 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B
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