Altimetric Data Assimilation by EnOI and 3DVAR in a Tropical Pacific Model: Impact on the Simulation of Variability |
| |
Authors: | FU Weiwei |
| |
Institution: | EnOI, 3DVAR, SLA assimilation, Tropical Pacific, variability |
| |
Abstract: | When altimetric data is assimilated, 3DVAR and Ensemble Optimal
Interpolation (EnOI) have different ways of projecting the surface
information downward. In 3DVAR, it is achieved by minimizing a cost function
relating the temperature, salinity, and sea level. In EnOI, however, the
surface information is propagated to other variables via a stationary
ensemble. In this study, the differences between the two methods were
compared and their impacts on the simulated variability were evaluated in a
tropical Pacific model.
Sea level anomalies (SLA) from the TOPEX/Poseidon were assimilated using
both methods on data from 1997 to 2001 in a coarse resolution model. Results
show that the standard deviation of sea level was improved by both methods,
but the EnOI was more effective in the central/eastern Pacific. Meanwhile,
the SLA evolution was better reproduced with EnOI than with 3DVAR.
Correlations of temperature with the reanalysis data increased with EnOI by
0.1--0.2 above 200 m. In the eastern Pacific below 200 m, the correlations
also increased by 0.2. However, the correlations decreased with 3DVAR in
many areas. Correlations with the independent TAO profiles were also
compared at two locations. While the correlations increased by up to 0.2 at
some depths with EnOI, 3DVAR generally reduced the correlations by 0.1--0.3.
Though both methods were able to reduce the model--data difference in
climatological sense, 3DVAR appears to have degraded the simulated
variability, especially during El Nino--Southern Oscillation events. For
salinity, similar results were found from the correlations. This tendency
should be considered in future SLA assimilations, though the comparisons may
vary among different model implementations. |
| |
Keywords: | EnOI 3DVAR SLA assimilation Tropical Pacific variability |
本文献已被 CNKI SpringerLink 等数据库收录! |
| 点击此处可从《大气科学进展》浏览原始摘要信息 |
| 点击此处可从《大气科学进展》下载免费的PDF全文 |
|