南海中尺度涡的时空变化规律Ⅰ.统计特征分析
Temporal and spatial variation characteristics on eddies in the South China Sea Ⅰ. Statistical analyses
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摘要: 利用TOPEX/Poseidon混合ERS1/2高度计资料对1993~2002年间南海中尺度涡进行辨认和动态追踪,并对其时空变化规律进行统计分析,结果表明:南海平均每年出现18个涡旋,出现数量的年际变化与El Niño/La Niña有一定关系.多数涡旋的生命周期在180 d以内,近半数为30~60 d;半径大致在100 km到250 km间,其经向变化与斜压罗斯贝变形半径的经向变化趋势一致;80%的涡旋向西移动,纬向移速大致为在-8 cm/s到3 cm/s间,随纬度变化呈“∑”型分布.涡旋发生的区域主要位于越南南部以东至台湾西南一线海域,呈东北-西南向分布,其中,吕宋海峡以西海域和越南南部以东海域涡旋的出现概率相对较大,约为23%和25%,是涡旋的高发区.涡旋的存在对水深大于200 m海域的海面高度变化的平均贡献约为36%,在涡旋高发区的贡献高达80%.从涡旋出现地点、传播路径和速度、出现概率及对海面高度变化的贡献综合来看,涡旋大体可以沿17°N分成南北两个相对独立系统,一般不会有涡旋跨系统传播.Abstract: Mesoscale eddies were identified and traced in the South China Sea (SCS) from 1993 to 2001 using TOPEX/Poseidon merged ERS-1/2 altimeter data through several criteria.Their space-time variation characteristics were statistically analyzed.Averagely,there were about 18 eddies emerge annually in this region.The amount of eddies emerge annually may be related with ElNiño/La Niña.Generally,eddy life-times were less than 180 days and mainly ranged from 30 to 60 days.Eddy radiiranged from 100 km to 250 km and followed up with the baroclinic Rossby deformation radii.About 80% eddies moved westward.Eddy zonal moving speeds ranged from -8 cm/s to 3 cm/s and changed meridionally like a "E" style.Eddies were active along a band from east of Southern Vietnam to Southwest of Taiwan in the northeast-southwest direction.Statistically calculated on 2°×2°grids,areas of relatively large eddy occurrence probabilities (OPs) were found located to the west of the Luzon Strait and to the east of Southern Vietnam with probabilities of about 23% and 25%,respectively.In the area with depth > 200 m in the SCS,the mean contribution of eddies to the sea level undulation was 36%.The maximum contribution could reach as high as 80% where the rms of SLA was very high,like the relative large eddy occurrence probabilities to the west of the Luzon Strait and to the east of Southern Vietnam.From the places where eddies emerged,propagation paths and speeds,occurrence probabilities and the contributions to the sea level undulation,eddies in the SCS could be separated into two relatively independent systems bounded by 17°N,where eddies could not propagate across.
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Key words:
- mesoscale eddies /
- sea level anomaly /
- occurrence probability /
- contribution
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