17:15 〜 18:45
[ACG40-P09] 東シナ海黒潮の経年変動の統計的解析
キーワード：黒潮、東シナ海
The Kuroshio in the East China Sea (ECS), which flows into the ECS from the east of Taiwan and out into the Pacific Ocean from the south of Kyushu, plays an important role in heat transport from from low to mid latitudes.
The interannual variation of the Kuroshio intensity is related to the large-scale wind field associated with the Pacific Decadal Oscillation (PDO) and the westward propagating mesoscale eddy. On the other hand, few studies have investigated the long-term interannual variation of the Kuroshio current pattern in the ECS. Here, this study clarifies the interannual variation of the Kuroshio pattern in the ECS. The ORAS5 monthly mean current near the surface layer are used in this study. The analysis period is from 1958 to 2022. EOF (Empirical Orthogonal Function) analysis is conducted for the current anomalies in the Kuroshio area of the ECS, excluding the inflow and outflow areas where interannual variability is large. The EOF 1st mode is a pattern in which the Kuroshio becomes stronger (weaker) while meandering slightly. The EOF 2nd mode shows a strong (weak) pattern on the east side and a weak (strong) pattern on the west side. Similar patterns were observed in the self-organizing map analysis.
The mean current anomalies at the time of the appearance of these patterns and at the preceding months were obtained. For example, in the case of the weakening of the Kuroshio in the 1st EOF mode, counterclockwise current anomalies were observed around the Luzon Strait prior to the weakening. In the eastern part of Taiwan, the current anomaly that weakens the Kuroshio is large. On the other hand, in the pattern of stronger Kuroshio in the EOF mode 1, there is a large current anomaly with stronger Kuroshio on the east side of Taiwan. However, the clockwise current anomalies around the Luzon Strait are not so clear. In the case of current anomalies corresponding to the EOF mode 2, the current anomalies east of Taiwan are small on average in both cases.
The correlation between the time coefficients of the EOF 1st or 2nd modes of the current anomalies in the Kuroshio region of the ECS and the PDO index was small. Lag correlations with EOF time coefficients of wind anomalies in various regions were also obtained. The correlation was slightly high for wind anomalies in the eastern Pacific in the tropical and subtropical regions. In the future, we will investigate the relationship with the phenomena preceding the pattern of the Kuroshio in the ECS. The relationship with wind and heat fluxes will also be investigated.
The interannual variation of the Kuroshio intensity is related to the large-scale wind field associated with the Pacific Decadal Oscillation (PDO) and the westward propagating mesoscale eddy. On the other hand, few studies have investigated the long-term interannual variation of the Kuroshio current pattern in the ECS. Here, this study clarifies the interannual variation of the Kuroshio pattern in the ECS. The ORAS5 monthly mean current near the surface layer are used in this study. The analysis period is from 1958 to 2022. EOF (Empirical Orthogonal Function) analysis is conducted for the current anomalies in the Kuroshio area of the ECS, excluding the inflow and outflow areas where interannual variability is large. The EOF 1st mode is a pattern in which the Kuroshio becomes stronger (weaker) while meandering slightly. The EOF 2nd mode shows a strong (weak) pattern on the east side and a weak (strong) pattern on the west side. Similar patterns were observed in the self-organizing map analysis.
The mean current anomalies at the time of the appearance of these patterns and at the preceding months were obtained. For example, in the case of the weakening of the Kuroshio in the 1st EOF mode, counterclockwise current anomalies were observed around the Luzon Strait prior to the weakening. In the eastern part of Taiwan, the current anomaly that weakens the Kuroshio is large. On the other hand, in the pattern of stronger Kuroshio in the EOF mode 1, there is a large current anomaly with stronger Kuroshio on the east side of Taiwan. However, the clockwise current anomalies around the Luzon Strait are not so clear. In the case of current anomalies corresponding to the EOF mode 2, the current anomalies east of Taiwan are small on average in both cases.
The correlation between the time coefficients of the EOF 1st or 2nd modes of the current anomalies in the Kuroshio region of the ECS and the PDO index was small. Lag correlations with EOF time coefficients of wind anomalies in various regions were also obtained. The correlation was slightly high for wind anomalies in the eastern Pacific in the tropical and subtropical regions. In the future, we will investigate the relationship with the phenomena preceding the pattern of the Kuroshio in the ECS. The relationship with wind and heat fluxes will also be investigated.