DOI: 10.1007/s00382-015-2860-2
Scopus记录号: 2-s2.0-84944595099
论文题名: Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere
作者: Kim J. ; Reichler T.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2016
卷: 47, 期: 2017-01-02 起始页码: 637
结束页码: 649
语种: 英语
英文关键词: Annular mode time scale
; Dynamical sensitivity
; Internal variability
; Stratosphere–troposphere coupling
英文摘要: The proper simulation of the annular mode time scale may be regarded as an important benchmark for climate models. Previous research demonstrated that this time scale is systematically overestimated by climate models. As suggested by the fluctuation–dissipation theorem, this may imply that climate models are overly sensitive to external forcings. Previous research also made it clear that calculating the AM time scale is a slowly converging process, necessitating relatively long time series and casting doubts on the usefulness of the historical reanalysis record to constrain climate models in terms of the annular mode time scale. Here, we use long control simulations with the coupled and uncoupled version of the GFDL climate model, CM2.1 and AM2.1, respectively, to study the effects of internal atmospheric variability and forcing from the lower boundary on the stability of the annular mode time scale. In particular, we ask whether a model’s annular mode time scale and dynamical sensitivity can be constrained from the 50-year-long reanalysis record. We find that internal variability attaches large uncertainty to the annular mode time scale when diagnosed from decadal records. Even under the fixed forcing conditions of our long control run at least 100 years of data are required in order to keep the uncertainty in the annular mode time scale of the Northern Hemisphere to 10 %; over the Southern Hemisphere, the required length increases to 200 years. If nature’s annular mode time scale over the Northern Hemisphere is similarly variable, there is no guarantee that the historical reanalysis record is a fully representative target for model evaluation. Over the Southern Hemisphere, however, the discrepancies between model and reanalysis are sufficiently large to conclude that the model is unable to reproduce the observed time scale structure correctly. The effects of ocean coupling lead to a considerable increase in time scale and uncertainty in time scale, effects which are noticeable in both troposphere and stratosphere. We further use the model simulation to investigate the dynamical coupling between the stratosphere and the troposphere from the perspective of the annular mode time scale. Over the Northern Hemisphere, we find only weak indication for influences from stratosphere–troposphere coupling on the annular mode time scale. The situation is very different over the Southern Hemisphere, where we find robust connections between the annular mode time scale in the stratosphere and that in the troposphere, confirming and extending earlier results of influences of stratospheric variability on the troposphere. © 2015, Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/53655
Appears in Collections: 过去全球变化的重建
There are no files associated with this item.
作者单位: Department of Atmospheric Sciences, University of Utah, 135 S 1460 East RM 819 (WBB), Salt Lake City, UT, United States; School of Earth and Environmental Sciences, Seoul National University, Seoul, South Korea
Recommended Citation:
Kim J.,Reichler T.. Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere[J]. Climate Dynamics,2016-01-01,47(2017-01-02)