Image_1_Upper-ocean structure variability in the Northwest Pacific Ocean in response to tropical cyclones.jpeg

The upper ocean structure obviously affects sea surface temperature cooling (SSTC) induced by tropical cyclones (TCs). Herein, principal component analysis of many Argo profiles from 2001 to 2017 in the Northwest Pacific Ocean is used to classify the upper ocean structure. The results suggest that the upper ocean structure can be divided into four types of water. Water with low mode 1 scores (M1-L water) is characterized by an extremely warm sea surface temperature (SST), while a cold and thick isothermal layer is observed for water with high mode 1 scores (M1-H water). Water with high mode 2 scores (M2-H water) has a warm SST and a thick isothermal layer. Relative to M2-H water, water with high mode 3 scores (M3-H water) has a warmer SST but a shallower mixed layer. These waters have remarkable seasonal and spatial variability, mainly associated with the impacts of solar radiation, precipitation, currents and mesoscale eddies. The ocean responses to TCs are different among these water types, which greatly influences the TCs intensification. The response of M1-H water is not considered, since its SST is below 26°C. The TC-induced SSTC of M3-H water (-1.12°C) is markedly higher than that of M1-L (-0.68°C) and M2-H waters (-0.41°C). Moreover, the one-dimensional mixed layer model shows a much smaller entrainment rate for M2-H water due to its thick barrier layer. The number of each water type changes in association with global warming and Kuroshio path, and thus affects the TC intensification.</p

DataSheet_1_Decadal intensified and slantwise Subpolar Front in the Japan/East Sea.zip

The Subpolar Front in the Japan/East Sea (JES) could far-reaching influence the atmospheric processes over the downstream regions. However its variability on decadal timescale remains less understood. In this study, the decadal trends in the intensity and position of the SPF in the JES during the time period 1985−2020 are analyzed by using four categories of satellite observed high-resolution sea surface temperature products. The results show that there is a significant intensification trend of the SPF at a rate of 0.37°C/100km/decade. The SPF is further divided into three regions based on the meridional sea surface temperature gradient (MSSTG): the eastern (135−138°E), central (130−135°E) and western (128−130°E) regions, respectively. These three regions showed different meridional movements with the eastern SPF moving poleward by 0.08°/decade, the central SPF moving equatorward by −0.11°/decade and the western SPF showing no significant displacements. The reverse meridional movements between the central and eastern SPF increased its skewness. The frontogenesis rate equation is employed to identify the mechanisms of these decadal trends. Results show that the geostrophic advection term, especially its zonal component, had a crucial role in the decadal trends of the intensity and position of the central and eastern SPF. The decadal trend of the central SPF was mainly attributed to the zonal geostrophic advection of the MSSTG associated with the enhancement of the Subpolar Front Current (SFC) in the upstream region, whereas the decadal trend in the eastern SPF was mainly driven by the zonal geostrophic shear advection controlled by the shear of the SFC in the downstream region. Before 2002, the eastern SPF moved poleward at a rate of 0.27°/decade, whereas there was no obvious trend after 2002. Further decomposition showed that this shift was caused by meridional Ekman advection of the MSSTG.</p