黑潮入侵呂宋海峽對區域大氣的影響

Abstract

黑潮是北太平洋的西方邊界流，其流經呂宋海峽的區段有時會以套流(loop current) 的型態向西入侵北南海。過往研究已證實台灣東北黑潮海表面溫度變異可對區域大氣帶來影響，本研究欲藉由衛星觀測資料及數值模式探討呂宋海峽黑潮套流入侵南海的事件是否對區域大氣造成影響。研究結果顯示東風期間（11－4月），臺灣西南外海因黑潮入侵所帶來海表增溫會伴隨近海表風速及降雨有增加的現象。近一步利用大氣數值模式WRF（Weather Research and Forecast model）以理想實驗對照有無黑潮套流入侵南海的情況下區域性大氣的差異，結果顯示黑潮入侵所伴隨的較高海表溫會增強低層大氣的垂直運動，並使垂直風切減弱，增加垂直混合效應，因而使近海表風速與降雨率增強。The Kuroshio is the western boundary current of the North Pacific Ocean. Kuroshio intrudes into the north of South China Sea (SCS) through the Luzon Strait. The intruded Kuroshio often forms an anticyclonic current loop north of the Luzon Strait. Previous studies confirmed covariability of sea surface temperature (SST) influence on the local atmosphere. In this study, by using satellite data and numerical modeling, the impact of Kuroshio intrusion (KI) entering north Luzon Strait on the local atmosphere is investigated. First, satellite data analysis shows that KI causing increased local sea surface temperature and enhanced intensity of wind speed and rainfall off southwestern Taiwan during easterly winds (from November to April). Using the WRF (Weather Research and Forecast model) model, we conduct two suites of idealized experiments for comparing the difference of local atmosphere responses due to KI entering the north of SCS or not. The result shows that higher local SST (associated with KI) triggering enhanced wind speed and rainfall by enhancing lower atmosphere vertical motion and thus decreasing vertical wind shear, which leads to intensify of vertical mixing.