Abstract
Studying the interaction between the upper ocean and the typhoons is crucial to improve our understanding of heat and momentum exchange between the ocean and the atmosphere. In recent years, the upper ocean responses to typhoons have received considerable attention. The sea surface cooling (SSC) process has been repeatedly discussed. In the present work, case studies were examined on five strong and super typhoons that occurred in 2016—LionRock, Meranti, Malakas, Megi, and Chaba—to search for more evidence of SSC and new features of typhoons’ impact on sea surface features. Monitoring data from the Central Meteorological Observatory, China, sea surface temperature (SST) data from satellite microwave and infrared remote sensing, and sea level anomaly (SLA) data from satellite altimeters were used to analyze the impact of typhoons on SST, the relationship between SSC and pre-existing eddies, the distribution of cold and warm eddies before and after typhoons, as well as the relationship between eddies and the intensity of typhoons. Results showed that: (1) SSC generally occurred during a typhoon passage and the degree of SSC was determined by the strength and the translation speed of the typhoon, as well as the pre-existing sea surface conditions. Relatively lower sea level (or cold core eddy) favors causing intense SSC; (2) After a typhoon passed, the SLA obviously decreased along with the SSC. The pre-existing positive SLAs or warm eddies decreased or disappeared during the typhoon’s passage, whereas negative SLAs or cold eddies were enhanced. It is suggested that the presence of warm eddies on the path has intensified the typhoons; (3) A criterion based on the ratio of local inertial period to application time of the typhoon wind-forcing was raised to dynamically distinguish slow- and fast-moving typhoons. And subcritical (slow-moving) situations were found in the LionRock case at its turning points where a cold core eddy was generated by long-time forcing. Moreover, the LionRock developed into a super typhoon due to reduced negative feedback when it was stalling over a comparably warmer sea surface. Therefore, the distinctive LionRock case is worthy of further discussion.
Highlights
The Northwestern Pacific Ocean is the largest ocean area with typhoons, hurricanes, or tropical cyclones, accounting for more than 30% of the total number worldwide [1]
Through the analysis of sea surface temperature (SST) data and sea level anomaly (SLA) data from ocean remote we found that the typhoon-induced cooling of the sea surface is roughly distributed on the left and sensing, we found that the typhoon-induced cooling of the sea surface is roughly distributed on the right sides of the typhoon track, with a range of about 100 km
We found that the mesoscale eddies, which existed in the upper ocean before the typhoon, played an important role in the extent and location of the cooling of the sea surface, and had an important impact on the typhoon intensity during the typhoon passage
Summary
The Northwestern Pacific Ocean is the largest ocean area with typhoons, hurricanes, or tropical cyclones, accounting for more than 30% of the total number worldwide [1]. It is generally thought that typhoons play an important role in regulating the momentum, heat, and material exchange between the upper. One of the most remarkable responses of the ocean is a significant reduction in sea surface temperature (SST) [7,8,9,10,11,12,13,14], known as sea surface cooling (SSC). The left side of the typhoon track may experience significant SSC due to intense precipitation [21,22]. The degree of SSC is generally thought to be determined by the intensity and translation speed of the typhoon and the pre-existing ocean conditions, such as SST, sea surface height (SSH), mixed layer depth (MLD), thermocline structure, etc
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