基于ROMS(Regional Ocean Modeling System)模式建立一个南海北部集合最优插值的同化系统,并且利用2008年夏季SCOPE(Northern South China Sea Coastal Oceanographic Process Experiment)航次的温盐数据以及航次期间逐日OSTIA(Operatio...基于ROMS(Regional Ocean Modeling System)模式建立一个南海北部集合最优插值的同化系统,并且利用2008年夏季SCOPE(Northern South China Sea Coastal Oceanographic Process Experiment)航次的温盐数据以及航次期间逐日OSTIA(Operational Sea Surface Temperature and Sea Ice Analysis)数据进行同化试验。试验结果表明:同化较好地改善了海表温度的模拟,加强了南海北部的上升流,尤其是加强了珠江冲淡水的模拟,垂向定量的分析表明,温度整层都得到改善,表层改善达到30%,盐度在80 m以上得到明显改善,表层改善40%。此外,针对近岸卫星SST(sea surface temperature)和航次SST的不协调性问题以及不同观测数量对同化结果的影响,利用敏感性同化试验进行了初步探讨,结果显示:相对于剔除40 m以浅,同化所有区域内卫星SST资料能显著减小近岸区域的SST均方根误差(约51%);加密用于同化的SST数据量,如由每隔5个格点调整为每隔3个格点选取观测数据,也能在此基础上再减小SST的均方根误差(约9.1%),但二者的SST分布形态均与观测吻合。展开更多
The global project of the Array for Real-time Geostrophic Oceanography （ARGO） provides a unique opportunity to observe the absolute velocity in mid-depths of the world oceans. A total of 1597 velocity vectors at 10...The global project of the Array for Real-time Geostrophic Oceanography （ARGO） provides a unique opportunity to observe the absolute velocity in mid-depths of the world oceans. A total of 1597 velocity vectors at 1000 （2000） db in the tropical Pacific derived from the ARGO float position information during the period November 2001 to October 2004 are used to evaluate the intermediate currents of the National Centers for Environmental Prediction reanalysis. To derive reliable velocity information from ARGO float trajectory points, a rigorous quality control scheme is applied, and by virtue of a correction method for reducing the drift error on the surface in obtaining the velocity vectors, their relative errors are less than 25%. Based on the comparisons from the quantitative velocity vectors and from the space-time average currents, some substantial discrepancies are revealed. The first is that the velocities of the reanalysis at mid-depths except near the equator are underestimated relative to the observed velocities by the floats. The average speed difference between NCEP and ARGO values ranges from about -2.3cm s^-1 to -1.8 cm s^-1. The second is that the velocity difference between the ocean model and the observations at 2000 dB seems smaller than that at 1000 dB. The third is that the zonal flow in the reanalysis is too dominant so that some eddies could not be simulated, such as the cyclonic eddy to the east of 160°E between 20°N and 30°N at 2000 dB. In addition, it is noticeable that many floats parking at 1000 dB cannot acquire credible mid-depth velocities due to the time information of their end of ascent （start of descent） on the surface in the trajectory files. Thus, relying on default times of parking, descent and ascent in the metadata files gravely confines their application to measuring mid-depth currents.展开更多
文摘基于ROMS(Regional Ocean Modeling System)模式建立一个南海北部集合最优插值的同化系统,并且利用2008年夏季SCOPE(Northern South China Sea Coastal Oceanographic Process Experiment)航次的温盐数据以及航次期间逐日OSTIA(Operational Sea Surface Temperature and Sea Ice Analysis)数据进行同化试验。试验结果表明:同化较好地改善了海表温度的模拟,加强了南海北部的上升流,尤其是加强了珠江冲淡水的模拟,垂向定量的分析表明,温度整层都得到改善,表层改善达到30%,盐度在80 m以上得到明显改善,表层改善40%。此外,针对近岸卫星SST(sea surface temperature)和航次SST的不协调性问题以及不同观测数量对同化结果的影响,利用敏感性同化试验进行了初步探讨,结果显示:相对于剔除40 m以浅,同化所有区域内卫星SST资料能显著减小近岸区域的SST均方根误差(约51%);加密用于同化的SST数据量,如由每隔5个格点调整为每隔3个格点选取观测数据,也能在此基础上再减小SST的均方根误差(约9.1%),但二者的SST分布形态均与观测吻合。
基金This research is supported by Natural Science Foundation of China(Contract No.40437017 and 40225015).
文摘The global project of the Array for Real-time Geostrophic Oceanography （ARGO） provides a unique opportunity to observe the absolute velocity in mid-depths of the world oceans. A total of 1597 velocity vectors at 1000 （2000） db in the tropical Pacific derived from the ARGO float position information during the period November 2001 to October 2004 are used to evaluate the intermediate currents of the National Centers for Environmental Prediction reanalysis. To derive reliable velocity information from ARGO float trajectory points, a rigorous quality control scheme is applied, and by virtue of a correction method for reducing the drift error on the surface in obtaining the velocity vectors, their relative errors are less than 25%. Based on the comparisons from the quantitative velocity vectors and from the space-time average currents, some substantial discrepancies are revealed. The first is that the velocities of the reanalysis at mid-depths except near the equator are underestimated relative to the observed velocities by the floats. The average speed difference between NCEP and ARGO values ranges from about -2.3cm s^-1 to -1.8 cm s^-1. The second is that the velocity difference between the ocean model and the observations at 2000 dB seems smaller than that at 1000 dB. The third is that the zonal flow in the reanalysis is too dominant so that some eddies could not be simulated, such as the cyclonic eddy to the east of 160°E between 20°N and 30°N at 2000 dB. In addition, it is noticeable that many floats parking at 1000 dB cannot acquire credible mid-depth velocities due to the time information of their end of ascent （start of descent） on the surface in the trajectory files. Thus, relying on default times of parking, descent and ascent in the metadata files gravely confines their application to measuring mid-depth currents.
