西沙周边海域海平面异常变化特征及成因分析

Based on the analysis of wind,ocean currents,sea surface temperature(SST) and remote sensing satellite altimeter data,the characteristics and possible causes of sea level anomalies in the Xisha sea area are investigated.The main results are shown as follows:(1) Since 1993,the sea level in the Xisha sea area was obviously higher than normal in 1998,2001,2008,2010 and 2013.Especially,the sea level in 1998 and 2010 was abnormally high,and the sea level in 2010 was 13.2 cm higher than the muti-year mean,which was the highest in the history.In 2010,the sea level in the Xisha sea area had risen 43 cm from June to August,with the strength twice the annual variation range.(2) The sea level in the Xisha sea area was not only affected by the tidal force of the celestial bodies,but also closely related to the quasi 2 a periodic oscillation of tropical western Pacific monsoon and ENSO events.(3)There was a significant negative correlation between sea level in the Xisha sea area and ENSO events.The high sea level anomaly all happened during the developing phase of La Ni?a.They also show significant negative correlations with Ni?o 4 and Ni?o 3.4 indices,and the lag correlation coefficients for 2 months and 3 months are–0.46 and –0.45,respectively.(4) During the early La Ni?a event form June to November in 2010,the anomalous wind field was cyclonic.A strong clockwise vortex was formed for the current in 25 m layer in the Xisha sea area,and the velocity of the current is close to the speed of the Kuroshio near the Luzon Strait.In normal years,there is a "cool eddy".While in 2010,from July to August,the SST in the area was 2–3°C higher than that of the same period in the history.

Characteristics and possible causes of sea level anomalies in the Xisha sea area

Based on the analysis of wind, ocean currents, sea surface temperature (SST) and remote sensing satellite altimeter data, the characteristics and possible causes of sea level anomalies in the Xisha sea area are investigated. The main results are shown as follows: (1) Since 1993, the sea level in the Xisha sea area was obviously higher than normal in 1998, 2001, 2008, 2010 and 2013. Especially, the sea level in 1998 and 2010 was abnormally high, and the sea level in 2010 was 13.2 cm higher than the muti-year mean, which was the highest in the history. In 2010, the sea level in the Xisha sea area had risen 43 cm from June to August, with the strength twice the annual variation range. (2) The sea level in the Xisha sea area was not only affected by the tidal force of the celestial bodies, but also closely related to the quasi 2 a periodic oscillation of tropical western Pacific monsoon and ENSO events. (3) There was a significant negative correlation between sea level in the Xisha sea area and ENSO events. The high sea level anomaly all happened during the developing phase of La Niña. They also show significant negative correlations with Niño 4 and Niño 3.4 indices, and the lag correlation coefficients for 2 months and 3 months are–0.46 and–0.45, respectively. (4) During the early La Niña event form June to November in 2010, the anomalous wind field was cyclonic. A strong clockwise vortex was formed for the current in 25 m layer in the Xisha sea area, and the velocity of the current is close to the speed of the Kuroshio near the Luzon Strait. In normal years, there is a “cool eddy”. While in 2010, from July to August, the SST in the area was 2–3°C higher than that of the same period in the history.