A regional reanalysis product-China Ocean Reanalysis（CORA）-has been developed for the China＇s seas and the adjacent areas. In this study, the intraseasonal variabilities（ISVs） in CORA are assessed by comparing wi...A regional reanalysis product-China Ocean Reanalysis（CORA）-has been developed for the China＇s seas and the adjacent areas. In this study, the intraseasonal variabilities（ISVs） in CORA are assessed by comparing with observations and two other reanalysis products（ECCO2 and SODA）. CORA shows a better performance in capturing the intraseasonal sea surface temperatures（SSTs） and the intraseasonal sea surface heights（SSHs） than ECCO2 and SODA do, probably due to its high resolution, stronger response to the intraseasonal forcing in the atmosphere（especially the Madden-Julian Oscillation）, and more available regional data for assimilation. But at the subsurface, the ISVs in CORA are likely to be weaker than reality, which is probably attributed to rare observational data for assimilation and weak diapycnal eddy diffusivity in the CORA model. According to the comparison results, CORA is a good choice for the study related to variabilities at the surface, but cares have to be taken for the study focusing on the subsurface processes.展开更多
The spatio-temporal variability modes of the sea surface height in the South China Sea（SCS-SSH） are obtained using the Cyclostationary Empirical Orthogonal Function（CSEOF） method, and their relationships to the Pa...The spatio-temporal variability modes of the sea surface height in the South China Sea（SCS-SSH） are obtained using the Cyclostationary Empirical Orthogonal Function（CSEOF） method, and their relationships to the Pacific basin scale oscillations are examined. The first CSEOF mode of the SCS-SSH is a strongly phase-locked annual cycle that is modulated by a slowly varying principal component（PC）; the strength of this annual cycle becomes reduced during El Ni？o events（at largest by 30% off in 1997/98） and enhanced during La Ni？a events. The second mode is a low frequency oscillation nearly on decadal time scale, with its spatial structure exhibiting an obscure month-dependence; the corresponding PC is highly correlated with the Pacific Decadal Oscillation（PDO） index.Five independent oscillations in the Pacific are isolated by using the independent component（IC） analysis（ICA）method, and their effects on the SCS-SSH are examined. It is revealed that the pure ENSO mode（which resembles the east Pacific ENSO） has little effect on the low frequency variability of the SCS-SSH while the ENSO reddening mode（which resembles the central Pacific ENSO） has clear effect. As the ENSO reddening mode is an important constituent of the PDO, this explains why the PDO is more important than ENSO in modulating the low frequency variability of SCS-SSH. Meridional saddle like oscillation mode, the Kuroshio extension warming mode, and the equatorial cooling mode are also successfully detected by the ICA, but they have little effect on the low frequency variability of the SCS-SSH. Further analyses suggest the Pacific oscillations are probably influencing the variability of the SCS-SSH in ways that are different from that of the sea surface temperature（SST） in the SCS.展开更多
基金The National Natural Science Foundation of China under contract Nos 41206178,41376034,41276018 and 41321004the Fundamental Research Funds for the Central Universities under contract No.2014B30514+1 种基金the open project supplied by the Key Laboratory of Marine Environmental Information Technology,National Marine Data and Information Service,State Oceanic Administration:Effectiveness on the intraseasonal scale in CORA(2015–2016)the Predictability of Ocean Dynamical System Project under Contract No.151053
文摘A regional reanalysis product-China Ocean Reanalysis（CORA）-has been developed for the China＇s seas and the adjacent areas. In this study, the intraseasonal variabilities（ISVs） in CORA are assessed by comparing with observations and two other reanalysis products（ECCO2 and SODA）. CORA shows a better performance in capturing the intraseasonal sea surface temperatures（SSTs） and the intraseasonal sea surface heights（SSHs） than ECCO2 and SODA do, probably due to its high resolution, stronger response to the intraseasonal forcing in the atmosphere（especially the Madden-Julian Oscillation）, and more available regional data for assimilation. But at the subsurface, the ISVs in CORA are likely to be weaker than reality, which is probably attributed to rare observational data for assimilation and weak diapycnal eddy diffusivity in the CORA model. According to the comparison results, CORA is a good choice for the study related to variabilities at the surface, but cares have to be taken for the study focusing on the subsurface processes.
基金The National Natural Science Foundation of China under contract Nos 91128204,41321004,41475101 and 41421005the National Basic Research Program(973 Program)of China under contract No.2013CB430302+1 种基金the Natural Science Foundation of China-Shandong Joint Fund for Marine Science Research Centers under contract No.U1406401the Strategic Priority Project of Chinese Academy of Sciences under contract Nos XDA11010301 and XDA11010104
文摘The spatio-temporal variability modes of the sea surface height in the South China Sea（SCS-SSH） are obtained using the Cyclostationary Empirical Orthogonal Function（CSEOF） method, and their relationships to the Pacific basin scale oscillations are examined. The first CSEOF mode of the SCS-SSH is a strongly phase-locked annual cycle that is modulated by a slowly varying principal component（PC）; the strength of this annual cycle becomes reduced during El Ni？o events（at largest by 30% off in 1997/98） and enhanced during La Ni？a events. The second mode is a low frequency oscillation nearly on decadal time scale, with its spatial structure exhibiting an obscure month-dependence; the corresponding PC is highly correlated with the Pacific Decadal Oscillation（PDO） index.Five independent oscillations in the Pacific are isolated by using the independent component（IC） analysis（ICA）method, and their effects on the SCS-SSH are examined. It is revealed that the pure ENSO mode（which resembles the east Pacific ENSO） has little effect on the low frequency variability of the SCS-SSH while the ENSO reddening mode（which resembles the central Pacific ENSO） has clear effect. As the ENSO reddening mode is an important constituent of the PDO, this explains why the PDO is more important than ENSO in modulating the low frequency variability of SCS-SSH. Meridional saddle like oscillation mode, the Kuroshio extension warming mode, and the equatorial cooling mode are also successfully detected by the ICA, but they have little effect on the low frequency variability of the SCS-SSH. Further analyses suggest the Pacific oscillations are probably influencing the variability of the SCS-SSH in ways that are different from that of the sea surface temperature（SST） in the SCS.
