DOI: 10.1007/s00382-016-2995-9
Scopus记录号: 2-s2.0-84955613816
论文题名: Diagnosing the possible dynamics controlling Sahel precipitation in the short-range ensemble community atmospheric model hindcasts
作者: Tseng Y.-H. ; Lin Y.-H. ; Lo M.-H. ; Yang S.-C.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2016
卷: 47, 期: 2017-09-10 起始页码: 2747
结束页码: 2764
语种: 英语
英文关键词: Global climate model evaluation
; Land–atmosphere interaction
; Local ensemble transform Kalman filter (LETKF)
; Model uncertainty
; Sahel precipitation
英文摘要: The actual dynamics and physical mechanisms affecting the Sahel precipitation pattern and amplitude in the climate models remain under debate due to the inconsistent drying and rainfall variability/pattern among them. We diagnose the boreal summer rainfall pattern in the Sahel and its possible causes using short-range ensemble hindcasts based on NCAR community atmospheric model with the local ensemble transform Kalman filter (CAM-LETKF) data assimilation. The CAM-LETKF assimilation was conducted using 64 ensemble members with an assimilation cycle of 6-h. By comparing the superior and inferior groups within these 64 ensembles, we confirmed the influence of the Atlantic in the West Sahel rainfall (a robust feature in the ensembles) and a severe model bias resulting from erroneously modeled locations and magnitudes of low-level Sahara heat low (SHL) and African easterly jet (AEJ). This bias is highly related to atmospheric jet dynamics as shown in recent studies and local wave instability triggered mainly by the boundary-layer temperature gradient and amplified by land–atmosphere interactions. In particular, our results demonstrated that more accurate divergence and convergence fields resulting from improved SHL and AEJ in the superior groups enabled more accurate rainbelt patterns to be discerned, thus improving the ensemble mean model hindcast prediction by more than 25 % in precipitation and 16 % in temperature. We concluded that the use of low-resolution climate models to project future rainfall in the Sahel requires caution because the model hindcasts may quickly diverge even the same boundary conditions and forcings are applied. The model bias may easily grow up within a few months in the short-range CAM-LETKF hindcast, let along the free model centennial simulations. Unconstrained future climate model projections for the Sahel must more effectively capture the short-term key boundary-layer dynamics in the boreal summer to be credible regardless model dynamics and physics. © 2016, Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/53473
Appears in Collections: 过去全球变化的重建
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作者单位: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO, United States; Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan; Department of Atmospheric Sciences, National Central University, Jhong-Li, Taiwan
Recommended Citation:
Tseng Y.-H.,Lin Y.-H.,Lo M.-H.,et al. Diagnosing the possible dynamics controlling Sahel precipitation in the short-range ensemble community atmospheric model hindcasts[J]. Climate Dynamics,2016-01-01,47(2017-09-10)