DOI: 10.1007/s00382-012-1615-6
Scopus记录号: 2-s2.0-84886722359
论文题名: Optimal nudging strategies in regional climate modelling: Investigation in a Big-Brother experiment over the European and Mediterranean regions
作者: Omrani H. ; Drobinski P. ; Dubos T.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2013
卷: 41, 期: 2017-09-10 起始页码: 2451
结束页码: 2470
语种: 英语
英文关键词: Big Brother experiment
; Dynamical downscaling
; Internal variability
; Optimal nudging
; Regional climate modelling
; Uncertainty
英文摘要: The objective of this work is to gain a general insight into the key mechanisms involved in the impact of nudging on the large scales and the small scales of a regional climate simulation. A "Big Brother experiment" (BBE) approach is used where a "reference atmosphere" is known, unlike when regional climate models are used in practice. The main focus is on the sensitivity to nudging time, but the BBE approach allows to go beyond a pure sensitivity study by providing a reference which model outputs try to approach, defining an optimal nudging time. Elaborating upon previous idealized studies, this work introduces key novel points. The BBE approach to optimal nudging is used with a realistic model, here the weather research and forecasting model over the European and Mediterranean regions. A winter simulation (1 December 1989-28 February 1990) and a summer simulation (1 June 1999-31 August 1999) with a 50 km horizontal mesh grid have been performed with initial and boundary conditions provided by the ERA-interim reanalysis of the European Center for Medium-range Weather Forecast to produce the "reference atmosphere". The impacts of spectral and indiscriminate nudging are compared all others things being equal and as a function of nudging time. The impact of other numerical parameters, specifically the domain size and update frequency of the large-scale driving fields, on the sensitivity of the optimal nudging time is investigated. The nudged simulations are also compared to non-nudged simulations. Similarity between the reference and the simulations is evaluated for the surface temperature, surface wind and for rainfall, key variables for climate variability analysis and impact studies. These variables are located in the planetary boundary layer, which is not subject to nudging. Regarding the determination of a possible optimal nudging time, the conclusion is not the same for indiscriminate nudging (IN) and spectral nudging and depends on the update frequency of the driving large-scale fields τa. For IN, the optimal nudging time is around τ = 3 h for almost all cases. For spectral nudging, the best results are for the smallest value of τ used for the simulations (τ = 1 h) for frequent update of the driving large-scale fields (3 and 6 h). The optimal nudging time is 3 for 12 h interval between two consecutive driving large-scale fields due to time sampling errors. In terms of resemblance to the reference fields, the differences between the simulations performed with IN and spectral nudging are small. A possible reason for this very similar performance is that nudging is active only above the planetary boundary layer where small-scale features are less energetic. As expected from previous studies, the impact of nudging is weaker for a smaller domain size. However the optimal nudging time itself is not sensitive to domain size. The proposed strategy ensures a dynamical consistency between the driving field and the simulated small-scale field but it does not ensure the best "observed" fine scale field because of the possible impact of incorrect driving large-scale field. This type of downscaling provides an upper bound on the skill possible for recent historical past and twenty-first century projections. The optimal nudging strategy with respect to dynamic downscaling could add skill whenever the parent global model has some level of skill. © 2012 Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/54734
Appears in Collections: 过去全球变化的重建
There are no files associated with this item.
作者单位: Laboratoire de Météorologie Dynamique, Institut Pierre Simon Laplace, CNRS and Ecole Polytechnique, 91128 Palaiseau Cedex, France
Recommended Citation:
Omrani H.,Drobinski P.,Dubos T.. Optimal nudging strategies in regional climate modelling: Investigation in a Big-Brother experiment over the European and Mediterranean regions[J]. Climate Dynamics,2013-01-01,41(2017-09-10)