碩士 / 臺灣大學 / 大氣科學研究所 / 98 / The coupled atmosphere-ocean seasonal prediction models have been extensively used nowadays. Compared with the stand-alone atmospheric models or ocean models, the coupled atmosphere and ocean models have higher skills in seasonal prediction, and especially their multi-model ensemble (MME), which more accurately make the 1-month lead seasonal forecast. On the other hand, the coupled atmosphere-ocean models still have deficiencies in reproducing realistic climatology.
The year-to-year variation of the Asian-Australia monsoon exhibits enormous regional differences and depends strongly on the phase of the annual cycle. This poses a great challenge for the coupled atmosphere-ocean model in making realistic seasonal simulation. This problem was clearly demonstrated in Wang et al. (2007), which analyzed the seasonal hindcast by the DEMETER and APCC/CliPAS.
This study is aimed to evaluate the capability of the DEMETER and NCEP/CFS in hindcasting the interannual variability of the East Asian monsoon for the 1980-2003 period. A preliminary analysis of the 2-meter temperature indicates that the hindcast skill of these coupled models is significantly higher in the ocean than over the continent. Especially, the simulated interannual variance in continent is significantly underestimated.
Compared with the simulation skill between high latitude area (20N~90N) and Tropical ocean area (20S~20N), most of the models are able to simulate the variance in low latitude but high latitude.
An EOF and SVD analysis of the East Asian monsoon indicates that while the models are able to simulate the leading circulation/precipitation coupled mode, they tend to put too much weight on the leading mode by exaggerating the fractional variance explained by the leading mode. It suggests that the models tend to produce lower variability than the observed and is likely to misrepresent the variability that is not associated with the leading mode.
In our study, we found that the AOGCMs tend to show the feature of ENSO and lead by Tropical Ocean but ignore the variance in high latitude and land. This result reveals that the air-sea interaction is reasonably simulated, but the dynamical processes over land and the possible effect of air-land interaction are poorly handled in the models. Overall, the AOGCMs may overestimate the impact of Tropical Ocean, underestimate the influence of continent, and high latitude.
Further analyses will focus on the simulation skill in high latitude. Besides, we will evaluate the performance of East Asian monsoon in IPCC models and define a set metrics for to evaluate the models’ capability in simulating the interannual variability of the East Asian monsoon. In addition to identify the deficiencies of the models for further improvement.
| Identifer | oai:union.ndltd.org:TW/098NTU05022032 |
| Date | January 2010 |
| Creators | Ping-Yuan Hung, 洪萍遠 |
| Contributors | 許晃雄 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 105 |
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