Modling of upper ocean heat budget variations in response to the passage of super Typhoon Sinlaku (2008) in the Western North Pacific

In 2008, Super Typhoon Sinlaku (2008) passed over a preexisting cyclonic eddy (PCE) in the western North Pacific, causing an extreme cooling response at 22.5°N, 125°E. This case provides a rare opportunity to explore the physical mechanisms that trigger an extreme cooling response to a typhoon underlying the influence of PCEs. In this study, cooling response to Sinlaku was observed by TMI/AMSR-E microwave SSTs and simulated using the Regional Ocean Modeling System. To elucidate the impact of a PCE, in addition to standard run (EXP_std), another experiment that eliminates the influence of a PCE (EXP_nonPCE) was designed and executed. By conducting upper ocean heat budget analysis on modeling diagnostic outputs, it is found that PCE enhances the cooling response by enhancing both the entrainment and upwelling simultaneously; but the dominant terms balancing the heat budget were not greatly altered by the PCE. Finally, the vertical thermal gradient is shown to be the essential factor boosting the enhancement of entrainment and upwelling, thus cooling the upper ocean.