南海中尺度涡的季节和年际变化特征分析

以11a(1993—2003年)TOPEX/Poseidon、Jason和ERS1/2高度计的融合资料为基础,统计了南海中尺度涡的时空分布,分析了南海中尺度涡的季节和年际变化,并结合QuikSCAT、ERS1/2风场资料初步探讨了南海中尺度涡形成的可能机制。研究结果表明,南海中尺度涡存在明显的季节和年际变化,而季风强迫是这种变化的主要驱动因素。冬季冷涡(气旋涡)主要分布在吕宋岛西北和越南东南海域,而暖涡(反气旋涡)主要在18°N以北出现。春季暖涡在南海中部开始出现并得到充分发展。夏季暖涡明显多于冷涡,暖涡主要分布在越南东南和吕宋岛西北海域,而冷涡分布于越南以东和南海东北部。秋季冷涡主要分布在越南沿岸,暖涡则分布在南海东北部;11a海面高度异常均方根的时空分布变化也显示了南海中尺度涡存在较强的年际变化。     

Estimation of annual variation of water vapor in the Arctic Ocean between 80°–87°N using shipborne GPS data based on kinematic precise point positioning

The measurement of atmospheric water vapor(WV) content and variability is important for meteorological and climatological research. A technique for the remote sensing of atmospheric WV content using ground-based Global Positioning System(GPS) has become available, which can routinely achieve accuracies for integrated WV content of 1–2 kg/m2. Some experimental work has shown that the accuracy of WV measurements from a moving platform is comparable to that of(static) land-based receivers. Extending this technique into the marine environment on a moving platform would be greatly beneficial for many aspects of meteorological research, such as the calibration of satellite data, investigation of the air-sea interface, as well as forecasting and climatological studies. In this study, kinematic precise point positioning has been developed to investigate WV in the Arctic Ocean(80°–87°N) and annual variations are obtained for 2008 and 2012 that are identical to those related to the enhanced greenhouse effect.     

Statistical characteristics and thermohaline properties of mesoscale eddies in the Bay of Bengal

The statistical characteristics and vertical thermohaline properties of mesoscale eddies in the Bay of Bengal are studied from the view of satellite altimetry data and Argo profiles. Eddy propagation preferences in different lifetimes, eddy evolution process, and geographical distribution of eddy kinetic properties are analyzed in this area. Eddies exist principally in the western Bay of Bengal, and most of them propagate westward. There is a clear southward(equatorward) preference for eddies with long lifetimes, especially for cyclones. Moreover, the eddies in different areas of the bay show different north-southward preferences. Evolution of eddy kinetic properties with lifetime shows that eddies have the significant three-stage feature: the growth period in the former one-fifth lifetime, the stable period in the middle two-fifth to four-fifth lifetime, and the dying period in the last one-fifth lifetime. Large-amplitude and high-intensity eddies occur only in the relatively confined regions of highly unstable currents, such as the East Indian Coastal Current and eastern Sri Lanka. Based on Argo profile data and climatology data, the eddy synthesis method was used to construct three-dimensional temperature and salt structures of eddies in this area. The mean temperature anomaly is negative/positive to the cyclonic/anticyclonic eddies in the upper 300×10~4 Pa, and below this depth, the anomaly becomes weak. The salinity structures of positive anomalies inside cyclonic eddies and negative anomalies inside anticyclonic eddies in the Bay of Bengal are not consistent with other regions. Due to the special characteristics of the water mass in the bay, especially under the control of the low-salinity Bay of Bengal water at the surface and the Indian equatorial water in the deep ocean, the salinity of seawater shows a monotonic increase with depth. For regional varieties of temperature and salinity structures, as the eddies move westward, the temperature anomaly induced by the eddies increases, the effecting depth of the eddies deepens, and the salinity structures are more affected by inflows. In the north-south direction, the salinity structures of the eddies are associated with the local water masses, which comprise lowsalinity water in the northern bay due to the inflow of freshwater from rivers and salty water in the southern bay due to the invasion of Arabian Sea high-salinity water from the north Indian Ocean.     

基于1993-2014年高度计数据的西北太平洋中尺度涡识别和特征分析

本文利用22年的AVISO卫星高度计融合数据,基于WA涡旋自动识别方法对西北太平洋的中尺度涡进行了识别追踪,并统计分析了研究区域中尺度涡的空间分布特征、运动属性以及季节和年际变化。研究结果表明:22年间共追踪到生命周期超过30 d的气旋涡3 841个,反气旋涡2 836个,气旋涡数量多于反气旋涡。涡旋大部分向西移动,西向传播的涡旋分布在整个研究区域,而东向传播的涡旋则集中在黑潮及其延伸区。涡旋主要存在15°~30°N的纬度带间;分别而言,气旋涡主要分布在研究区域的北部和南部,而反气旋涡主要分布在副热带逆流区。30°~35°N之间的黑潮延伸区具有明显更高的涡动能和涡振幅,与同纬度区域相比这里的涡旋半径也较高。在季节和年际变化上,春季出现的中尺度涡最多,夏季最少;对涡旋的月生成数目与ENSO指数MEI比较发现,西北太平洋涡旋活动变化并不直接与ENSO现象相关。     

孟加拉湾及其毗邻海域中尺度涡旋活动的冬、夏季差异

基于1993—2017年从卫星高度计资料中识别出来的中尺度涡轨迹数据集,对冬、夏季孟加拉湾涡旋的源地和性质进行了研究。研究表明孟加拉湾西部、安达曼海和孟加拉湾通往赤道的出口处的中尺度涡旋活动呈现显著的季节性差异。安达曼海在冬、夏季从北往南中尺度涡旋分别以"反气旋涡-气旋涡-反气旋涡"和"气旋涡-反气旋涡-气旋涡"的格局分布。不同源区涡旋的季节性生长过程有明显差异。孟加拉湾西部的涡旋在夏季生长迅速但消散缓慢,斯里兰卡冷涡生长缓慢但消散迅速。不同源区涡旋半径和振幅大小有不同的特征。孟加拉湾西部,无论冬、夏季,反气旋涡的振幅、半径都比气旋涡大;夏季季风漂流区,气旋涡半径比反气旋涡小但是振幅比反气旋涡大;安达曼海内无论冬、夏季都是最北侧聚集区涡旋的半径和振幅最大。孟加拉湾内生命史为30～40 d的涡旋数量最多,生命史在100 d以上的涡旋主要分布在孟加拉湾西部。     

孟加拉湾中尺度涡的总体特征与季节变化

采用AVISO提供的中尺度涡最新数据集,分析了孟加拉湾1993—2016年中尺度涡的总体特征和季节变化。结果表明:研究期间在孟加拉湾共有822个气旋涡,731个反气旋涡,主要分布在湾北部(15°N以北海域)和安达曼海。涡旋生命周期以28～59 d为主,平均振幅为7. 5 cm,平均半径为119. 6 km。在纬度变化上,涡旋振幅随纬度的增加有两个峰值,分别位于6°～9°N和15°～20°N之间,而涡旋半径随纬度增加而减少。涡旋的振幅、半径在随生命周期演变过程中生长过程较慢,消散过程较快。气旋涡和反气旋涡主要是向西移动,且均以向赤道方向偏移为主。在季节变化上,孟加拉湾较长生命周期(60 d以上)的中尺度涡具有明显的季节变化,春季生成的涡旋数量最多,冬季次之,夏季最少。通过合成分析得出风应力旋度是孟加拉湾中尺度涡季节变化的主要原因,而沿岸Kelvin波激发的西传Rossby波对涡旋的产生也有一定影响。涡动能分析表明,涡动能的高值区主要位于海盆的西边界和斯里兰卡东部海域,同时,在冬季、春季海盆的西边界和夏季、秋季海盆的北部涡旋活动较多的区域对应着较大的涡动能。     

印度洋–太平洋暖池区中尺度涡特征研究

本文利用1993年2月至2016年1月共23年的中尺度涡数据,对印度洋–太平洋暖池区（即印–太暖池区,15°S～15°N,60°E～170°W）中尺度涡的生命周期、振幅和半径等属性特征以及生命周期内各参数的演变特征进行了统计分析,并研究了印–太暖池区中尺度涡生成个数的季节变化规律及与厄尔尼诺循环的关系。结果表明：印–太暖池区大部分中尺度涡存在生命周期短、非线性、向西移动的特征;气旋涡与反气旋涡各参数的统计特征及其在生命周期内的变化趋势较为相似;印–太暖池区中尺度涡生成个数不具有明显的季节变化,并且会受到厄尔尼诺–南方涛动事件的影响。     

孟加拉湾海洋热浪季节变化特征与可能成因

本文基于1982−2021年的NOAA最优插值海表温度等资料,分析了孟加拉湾海洋热浪季节分布特征与可能成因。结果表明：大致以斯里兰卡岛与缅甸伊洛瓦底江河口连线为界,孟加拉湾西北部与东南部海域海洋热浪频率和天数呈现出不同的季节变化特征。在湾西北部海域,海洋热浪频率和天数季节变化较显著,均在夏季达到最大,春、秋季次之,冬季最少。而在湾东南部海域,二者的季节变化相对较弱。依据海洋热浪累积强度将海洋热浪从弱至强分为I～IV4种等级。分析显示,I类和II类较弱海洋热浪主要发生于夏、秋季的湾西部或西北部海域;III类以上严重海洋热浪则多发于春季的安达曼海和湾东南部海域以及夏季的缅甸西南部海域。进一步分析表明,在春、夏和秋季大部分海洋热浪活跃区,较浅的混合层及海表净热通量的变化对这些海区海洋热浪活动可能起主要作用,而冬季湾东南部海域海洋热浪形成与维持可能主要与赤道远地强迫有关。     

南海中尺度涡强度的季节和年际变化分析

为了研究南海中尺度涡强度的季节和年际变化规律,利用Matlab提取50 a(1958~2007年)简单海洋资料同化(Simple Ocean Data Assimilation,SODA)月平均数据集中流场和海表面高度场数据,应用一个涡旋自动探测算法对南海中尺度涡初始生成位置进行分析,并分析了海表面高度异常均方根值的季节变化和年际变化。结果表明:50 a里南海中尺度涡主要分布在吕宋岛西北海域、吕宋岛西南海域和越南以东广大海域,秋、冬季中尺度涡能量较高,春季中尺度涡最弱,中尺度涡强度高值区年际变化明显。从季节变化上看,海面高度异常均方根春、夏季最小,秋冬季最大;从年际变化上看,与同时期Nino3指数有显著负相关,周期大约为3 a。     

赤道东印度洋和孟加拉湾障碍层厚度的年际变化及其影响机制

Interannual variability(IAV) in the barrier layer thickness(BLT) and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO) and Bay of Bengal(BoB) are examined using monthly Argo data sets during 2002–2017. The BLT during November–January(NDJ) in the EEIO shows strong IAV, which is associated with the Indian Ocean dipole mode(IOD), with the IOD leading the BLT by two months. During the negative IOD phase, the westerly wind anomalies driving the downwelling Kelvin waves increase the isothermal layer depth(ILD). Moreover, the variability in the mixed layer depth(MLD) is complex. Affected by the Wyrtki jet, the MLD presents negative anomalies west of 85°E and strong positive anomalies between 85°E and 93°E. Therefore, the BLT shows positive anomalies except between 86°E and 92°E in the EEIO. Additionally, the IAV in the BLT during December–February(DJF) in the BoB is also investigated. In the eastern and northeastern BoB, the IAV in the BLT is remotely forced by equatorial zonal wind stress anomalies associated with the El Ni?o-Southern Oscillation(ENSO). In the western BoB, the regional surface wind forcing-related ENSO modulates the BLT variations.     

安达曼海中尺度涡季节变化分析

利用 AVISO 提供的中尺度涡数据集,对1993–2019年间安达曼海中尺度涡的涡旋特征、运动规律及其季节变化机制进行统计分析。结果显示,27年间安达曼海共出现中尺度涡328个,其中反气旋涡（171个）多于气旋涡（157个）,主要分布在中西部盆地深水区。涡旋平均寿命为46.4 d,平均半径为111.8 km,平均振幅为4.7 cm,平均最大转速为24.8 cm/s,平均移动速度为15.0 cm/s,反气旋涡的平均半径、振幅和转速均大于气旋涡,而移动速度小于气旋涡。涡旋的半径、振幅和最大转速在其生命周期中都经历了先增大后减小的过程,移动速度则先减小后增大。在季节变化方面,反气旋涡和气旋涡性质冬夏对比呈现“跷跷板”现象,即夏季气旋涡比反气旋涡更多更强更大,冬季则反气旋涡更多更强更大;涡旋分布位置,夏季从北向南呈“气旋–反气旋–气旋”的极性反转交替分布,冬季则与之相反。动力机制分析显示,背景流场涡度可能影响安达曼海涡旋极性交替分布,正（负）涡度背景流利于气旋（反气旋）涡存在。涡旋能量变化机制显示,风强迫是安达曼海涡旋主要能量来源,风场能量输入与涡旋动能的季节变化吻合。     

Statistical characteristics and mechanisms of mesoscale eddies in the North Indian Ocean

The statistical characteristics and mechanisms of mesoscale eddies in the North Indian Ocean are investigated by adopting multi-sensor satellite data from 1993 to 2019. In the Arabian Sea(AS), seasonal variation of eddy characteristics is remarkable, while the intraseasonal variability caused by planetary waves is crucial in the Bay of Bengal(BOB). Seasonal variation of the eddy kinetic energy(EKE) is distinct along the west boundary of AS,especially in the Somali Current region. In the BOB, lar...