南印度洋中尺度涡统计特征及三维合成结构研究

Statistical characteristics and composed three dimensional structures of mesoscale eddies in the South Indian Ocean

南印度洋是海洋中尺度涡的多发区域。本文利用卫星高度计资料及Argo浮标资料,对南印度洋(10°~35°S,50°~120°E)区域中尺度涡的分布、表观特征等进行了统计分析,采用合成方法,构建了该区域中尺度涡的三维温盐结构。结果表明,涡旋频率呈明显的纬向带状分布,在18°~30°S存在一个明显的涡旋频率带状高值区;涡旋半径具有由南至北逐渐增大的趋势;长周期涡旋在其生命周期内,半径、涡动能、涡能量密度、涡度等性质均经历了先增大而后减小的过程;涡旋以西向运动为主,在经向上移动距离较小,长周期气旋(反气旋)涡具有明显的偏向极地(赤道)移动的倾向;涡旋平均移动速度为5.9cm/s,速度大小大致沿纬向呈带状分布。在混合层以下,气旋涡(反气旋涡)内部分别呈现明显的温度负(正)异常,且分别存在两个位温负(正)异常的冷(暖)核结构;气旋涡(反气旋涡)整体上呈现"正—负"("负—正")上下层相反的盐度异常结构。中尺度涡对温盐的平均影响深度可达1 000×104 Pa以上。

The South Indian Ocean is a region abundant of mesoscale eddies. We analyzed statistical characteristics of mesoscale eddies in the South Indian Ocean（10°-35°S, 50°-120°E） based on merged satellite altimetry data as well as Argo profile data. The results show that eddy frequency is distinctly high in the band area between 18°- 30°S; eddy radius tend to increase from the south the north; the radius, eddy kinetic energy, energy intensity and vorticity of long-lived eddies firstly increased and then decreased as eddies evaluate during their lifespans. Most ed- dies propagate westward while their meridional movement is not significant and long-lived cyclonic eddies （CEs）and anticyclonic eddies （AEs） have poleward （equatorward） deflections, respectively. The mean propagation speedof eddies is 5.9 cm/s and the magnitude present a feature of zonal distribution. Under the mixing layer, CE （AE）represent consistent negative （positive） temperature anomaly and there exist two cold （warn） cores with negative（positive） temperature anomaly, respectively. The salinity structure of CE presented as ‘ positive-negative’ salinityanomaly structure, while it is opposite for AE. Eddies＇ influence on temperature and salinity could reach more than1 000 × 104 Pa.