Typhoon evolution related to sea surface characteristics in the Northwestern Pacific by using multi-satellite data

• Main Authors: Ya-Ting Chan, 詹雅婷
• Other Authors: Shih-Jen Huang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/87623900995175367798

碩士 === 國立臺灣海洋大學 === 海洋環境資訊學系 === 98 === The purpose of this thesis is to know the typhoon evolution related to sea surface characteristics by using best track, satellite data and hindcast output of model. Best track data from Japan Meteorological Agency is including longitude and latitude and near-center maximum wind speed (MWS). Satellite data is including sea surface temperature (SST), sea surface height anomaly (SSHA) and cloud top temperature (CTT) during typhoon period. Because the in-situ mixed layer depth (MLD) is not easy to get, we used the hindcast mixed layer depth of HYBIRD COORDINATE OCEAN MODEL (HYCOM). To estimate the heat content of upper ocean, we defined a heat content index (HCI) with the SST and MLD. The correlation coefficients between MWS and SSHA higher than 0.5 was about 46.2%; the correlation coefficients between CTT and SSHA lower than -0.5 was about 61.5%. From the correlation results, most of the bad relationship was during El Niño. During El Niño, the atmospheric condition was conducive to the formation of typhoon because of the lower vertical wind shear, but the ocean condition was worse than normal year because of the thinner mixed layer depth. We found out the atmosphere condition could make up a deficiency of sea surface characteristics. Unsupervised classification method is also used in this study. The classification method can distinguish the typhoon life time to different stage, and demonstrate the effect of sea surface characteristics on typhoon evolution. Considering classification results, HCI was an important factor at initial period of typhoon formation. During the stage of typhoon developed, warm eddy could offer more energy and then typhoon became stronger; cold eddy could suppress typhoon development. During the stage of typhoon decayed, warm eddy could delay the time of decaying.