RESUMO
Subtropical Mode Water (STMW), characterized by vertically uniform temperature of ~17°C, is distributed horizontally over 5000 kilometers at the 100- to 500-meter depths in the subtropical North Pacific Ocean. Its formation and spreading fluctuate in relation to the Pacific Decadal Oscillation and the Kuroshio path variation, but the feedback from STMW on the sea surface temperature (SST) and the overlying atmosphere remains unclear. Using Argo profiling float data, we show that STMW south of Japan, whose thickness varies decadally, modulates the overlying thermal structure throughout the year by increasing isotherm uplift with increasing thickness. The STMW-induced decadal temperature change has a magnitude of up to ~1°C and is large in the warm season in the presence of the seasonal thermocline. Furthermore, 50-year observations, together with numerical simulation, show that SST, upper ocean heat content, and typhoon intensification rate have been significantly lower in years with thicker STMW and higher in years with thinner STMW.
RESUMO
The influence of El Niño/Southern Oscillation (ENSO) on tropical cyclone (TC) activity in the western North Pacific (WNP) is investigated using a high-resolution atmosphere-ocean Coupled General Circulation Model (CGCM) developed by the National Research Institute for Earth Sciencie and Disaster Prevention. The CGCM simulation indicates the model TC activity associating with the ENSO as follows; (1)the frecuency of model TC in the WNP during the ENSO cold phase is slightly higher than during the ENSO warm phase (2)the genesis loction of model TC shifts eastward during the ENSO warm phase, (3)model TC tends to migrate westward during the ENSO warm phase and northward during the ENSO cold phase. These results are intimately related to variations in atmospheric circulaton and SST during the ENSO. Similar influences are also confirmed in the relationship between actual TC activity and actual ENSO. (AU)
