Eddy variations in the Western North Pacific South Eddy Zone by Satellite Altimetry Observation for Typhoon Intensification Research

Ocean eddy, one of the major oceanic phenomena, has been proved that is able to affect typhoon intensification, because it could alter the upper ocean thermal structure (UOTS). UOTS becomes warmer (colder) then climatology when a warm (cold) eddy exists, such kind of condition would be more (less) favorable for typhoon intensification. Therefore, there is great interest in investigating the variation of eddy in the ocean, which is expected to influence the typhoon's intensity variability. With 15 years of satellite altimetry data, we developed a new method to objectively identify and recognize eddies in the western North Pacific south eddy zone (i.e., 21-26°N, 127-170°E) during the typhoon season (i.e. May to October), it is one of the regions where have the most eddy-typhoon interaction. Two different kinds of eddies are studied: 1.) warm eddy characterized by positive sea surface height anomalies (SSHA), and 2.) cold eddy characterized by negative SSHA. The eddy number represents apparent annual and inter-annual variability. Besides, a significant trend is found in the number of warm and cold eddy between 1993 and 2007. The amount of warm eddy is increasing with the rate of 0.15/yr, while cold eddy is decreasing with the rate of -0.2/yr. Addition to the eddy number; it found that the intensity and the size of the warm eddy also tend to increase as well. In the other words, the warm eddy is getting more, bigger and more intense. Thus, it may probably change typhoons' characteristic in the western North Pacific.