A comparison between 3DVAR and EnOI techniques for satellite altimetry data assimilation |
| |
| Authors: | Weiwei Fu Jiang Zhu Changxiang Yan |
| |
| Institution: | aNansen-Zhu International Research Center (NZC), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, P.O. Box 9804, Beijing 100029, China;bInternational Centre for Climate and Environmental Sciences (ICCES), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;cLAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China |
| |
| Abstract: | Two conceptually different assimilation schemes, three dimensional variational (3DVAR) assimilation and Ensemble Optimum Interpolation (EnOI) are compared in the context of satellite altimetric data assimilation. Similarities and differences of the two schemes are briefly discussed and their impacts on the model simulation are investigated.With a tropical Pacific ocean model, two assimilation experiments of sea level anomaly (SLA) data from TOPEX/Poseidon are performed for 5 years from 1997 to 2001. Annual mean states of temperature and salinity fields are compared with analysis data and some independent observations. It is found that EnOI generally produces moderate improvements on both temperature and salinity fields, while changes induced by 3DVAR assimilation are strong and vary remarkably in different areas. For instance, 3DVAR tends to excessively modify the temperature field along the thermocline depth and even deteriorate the simulation, but it is more effective than EnOI below the thermocline depth. However, for the salinity field 3DVAR outperforms EnOI nearly for almost the whole layer. As the difference relative to the WOA01 analysis is compared, it is apparently reduced to below 0.3 psu in most areas in the 3DVAR experiment. On the other hand, the pattern of difference in the EnOI experiment resembles that of the simulation and the magnitude is only diminished to some extent. One advantage of EnOI is that it yields more consistent improvements even in areas where there are large model errors. It is more reliable than 3DVAR in such a sense. It is also revealed that the T–S relation plays a very important role in altimetric data assimilation. Further, the distinct performance of the two schemes can be partly accounted for by their inherent assumptions and settings. |
| |
| Keywords: | 3DVAR EnOI Comparison Satellite altimetric data |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
