Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathwa...Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathways and impact strength of Fuku-shima nuclear pollutants in the North Pacific have been estimated. The particulates are used to increase the sampling size and en- hance the representativeness of statistical results. The trajectories of the drifters and particulates are first examined to identify typical drifting pathways. The results show that there are three types of transport paths for nuclear pollutants at the surface： 1） most pollutant particles move eastward and are carried by the Kuroshio and Kuroshio-extension currents and reach the east side of the North Pacific after about 3.2-3.9 years; 2） some particles travel with the subtropical circulation branch and reach the east coast of China after about 1.6 years according to one drifter trajectory and about 3.6 years according to particulate trajectories; 3） a little of them travel with local, small scale circulations and reach the east coast of China after about 1.3-1.8 years. Based on the par-tieulates, the impact strength of nuclear pollutants at these time scales can be estimated according to the temporal variations of relative concentration combined with the radioactive decay rate. For example, Cesium-137, carried by the strong North Pacific current, mainly accumulates in the eastern North Pacific and its impact strength is 4% of the initial level at the originating Fuku- shima area after 4 years. Due to local eddies, Cesium-137 in the western North Pacific is 1% of the initial pollutant level after 1.5 years and continuously increases to 3% after 4 years. The vertical movement of radioactive pollutants is not taken into account in the present study, and the estimation accuracy would be improved by considering three-dimensional flows.展开更多
The impact of assimilating Argo data into an initial field on the short-term forecasting accuracy of temper- ature and salinity is quantitatively estimated by using a forecasting system of the western North Pacific, o...The impact of assimilating Argo data into an initial field on the short-term forecasting accuracy of temper- ature and salinity is quantitatively estimated by using a forecasting system of the western North Pacific, on the base of the Princeton ocean model with a generalized coordinate system （POMgcs）. This system uses a sequential multigrid three-dimensional variational （3DVAR） analysis scheme to assimilate observation da- ta. Two numerical experiments were conducted with and without Argo temperature and salinity profile data besides conventional temperature and salinity profile data and sea surface height anomaly （SSHa） and sea surface temperature （SST） in the process of assimilating data into the initial fields. The forecast errors are estimated by using independent temperature and salinity profiles during the forecasting period, including the vertical distributions of the horizontally averaged root mean square errors （H-RMSEs） and the horizontal distributions of the vertically averaged mean errors （MEs） and the temporal variation of spatially averaged root mean square errors （S-RMSEs）. Comparison between the two experiments shows that the assimila- tion of Argo data significantly improves the forecast accuracy, with 24% reduction of H-RMSE maximum for the temperature, and the salinity forecasts are improved more obviously, averagely dropping of 50% for H-RMSEs in depth shallower than 300 m. Such improvement is caused by relatively uniform sampling of both temperature and salinity from the Argo drifters in time and space.展开更多
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
Based on the statistics of all surface drifting buoys of 1978-2011 and Lagrangian tracers simulated from high quality ocean reanalysis currents,the impact times and strength of Fukushima nuclear pollution to the east ...Based on the statistics of all surface drifting buoys of 1978-2011 and Lagrangian tracers simulated from high quality ocean reanalysis currents,the impact times and strength of Fukushima nuclear pollution to the east coast of China and the west coast of America have been estimated.Under the circumstances of the radioactive pollutants drifting in the ocean surface,preliminary research results show that while the tracers took about 4 years to reach the west coast of USA,there are two types of tracers to carry out Fukushima nuclear pollutants to reach the east coast of China,corresponding to 1.5-year recirculation gyre transport and 3.5-year subtropical circulation transport.The distributions of the impact strength at these time scales are given according to the variation of relative number concentration with time combined with the decaying rate of radioactive matter.For example,starting from 1% at 1.5-year,of the initial level at the originating area of Fukushima nuclear pollution,the impact strength of Cesium-137 in the South China Sea continuously increases up to 3% by 4 years,while the impact strength of Cesium-137 in the west coast of America is as high as 4% due to the role of strong Kuroshio-extension currents as a major transport mechanism of nuclear pollutants for that area.展开更多
基金supported by the National Basic Research Program (Grant No.2013CB430304)the National Natural Science Foundation of China (Nos.41206178, 41030854, 41106005, 41176003 and 41306006)the National High-Tech R&D Program of China (No.2013 AA09A505)
文摘Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathways and impact strength of Fuku-shima nuclear pollutants in the North Pacific have been estimated. The particulates are used to increase the sampling size and en- hance the representativeness of statistical results. The trajectories of the drifters and particulates are first examined to identify typical drifting pathways. The results show that there are three types of transport paths for nuclear pollutants at the surface： 1） most pollutant particles move eastward and are carried by the Kuroshio and Kuroshio-extension currents and reach the east side of the North Pacific after about 3.2-3.9 years; 2） some particles travel with the subtropical circulation branch and reach the east coast of China after about 1.6 years according to one drifter trajectory and about 3.6 years according to particulate trajectories; 3） a little of them travel with local, small scale circulations and reach the east coast of China after about 1.3-1.8 years. Based on the par-tieulates, the impact strength of nuclear pollutants at these time scales can be estimated according to the temporal variations of relative concentration combined with the radioactive decay rate. For example, Cesium-137, carried by the strong North Pacific current, mainly accumulates in the eastern North Pacific and its impact strength is 4% of the initial level at the originating Fuku- shima area after 4 years. Due to local eddies, Cesium-137 in the western North Pacific is 1% of the initial pollutant level after 1.5 years and continuously increases to 3% after 4 years. The vertical movement of radioactive pollutants is not taken into account in the present study, and the estimation accuracy would be improved by considering three-dimensional flows.
基金The National Natural Science Foundation of China under contract Nos 41030854,41106005,41176003,and 41206178the National Science and Technology Support Program of China under contract No.2011BAC03B02-01-04
文摘The impact of assimilating Argo data into an initial field on the short-term forecasting accuracy of temper- ature and salinity is quantitatively estimated by using a forecasting system of the western North Pacific, on the base of the Princeton ocean model with a generalized coordinate system （POMgcs）. This system uses a sequential multigrid three-dimensional variational （3DVAR） analysis scheme to assimilate observation da- ta. Two numerical experiments were conducted with and without Argo temperature and salinity profile data besides conventional temperature and salinity profile data and sea surface height anomaly （SSHa） and sea surface temperature （SST） in the process of assimilating data into the initial fields. The forecast errors are estimated by using independent temperature and salinity profiles during the forecasting period, including the vertical distributions of the horizontally averaged root mean square errors （H-RMSEs） and the horizontal distributions of the vertically averaged mean errors （MEs） and the temporal variation of spatially averaged root mean square errors （S-RMSEs）. Comparison between the two experiments shows that the assimila- tion of Argo data significantly improves the forecast accuracy, with 24% reduction of H-RMSE maximum for the temperature, and the salinity forecasts are improved more obviously, averagely dropping of 50% for H-RMSEs in depth shallower than 300 m. Such improvement is caused by relatively uniform sampling of both temperature and salinity from the Argo drifters in time and space.
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supported by National Natural Science Foundation of China(Grant Nos. 41030854,40906015,40906016,41106005,and 41176003)
文摘Based on the statistics of all surface drifting buoys of 1978-2011 and Lagrangian tracers simulated from high quality ocean reanalysis currents,the impact times and strength of Fukushima nuclear pollution to the east coast of China and the west coast of America have been estimated.Under the circumstances of the radioactive pollutants drifting in the ocean surface,preliminary research results show that while the tracers took about 4 years to reach the west coast of USA,there are two types of tracers to carry out Fukushima nuclear pollutants to reach the east coast of China,corresponding to 1.5-year recirculation gyre transport and 3.5-year subtropical circulation transport.The distributions of the impact strength at these time scales are given according to the variation of relative number concentration with time combined with the decaying rate of radioactive matter.For example,starting from 1% at 1.5-year,of the initial level at the originating area of Fukushima nuclear pollution,the impact strength of Cesium-137 in the South China Sea continuously increases up to 3% by 4 years,while the impact strength of Cesium-137 in the west coast of America is as high as 4% due to the role of strong Kuroshio-extension currents as a major transport mechanism of nuclear pollutants for that area.
