Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2018-38
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Model evaluation paper
03 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Intraseasonal summer rainfall variability over China in the MetUM GA6 and GC2 configurations
Claudia Christine Stephan1, Nicholas P. Klingaman1, Pier Luigi Vidale1, Andrew G. Turner1,2, Marie-Estelle Demory1,3, and Liang Guo1 1National Centre for Atmospheric Science – Climate, Departm ent of Meteorology, University of Reading, P.O. Box 243, Reading RG6 6BB, United Kingdom
2Department of Meteorology, University of Reading, P.O. Box 243, Reading RG6 6BB, United Kingdom
3Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
Abstract. The simulation of intraseasonal precipitation variability over China in extended summer (May–October) is evaluated based on six climate simulations of the Met Office Unified Model. Two simulations use the Global Atmosphere 6.0 (GA6), and four the Global Coupled 2.0 (GC2) configuration. Model biases are large, such that mean precipitation and intraseasonal variability reach twice their observed values, particularly in southern China. To test the impact of air-sea coupling and horizontal resolution, GA6 and GC2 at horizontal resolutions corresponding to ~ 25, 60 and 135 km at 50° N are analyzed. Increasing the horizontal resolution and adding air-sea coupling have little effect on these biases. Pre-monsoon rainfall in the Yangtze River basin is too strong in all simulations. Simulated rainfall amounts in June are too high along the southern coast and persist in the coastal region through July, with only a weak northward progression. The observed northward propagation of the Meiyu/Baiu/Changma rainband from spring to late summer is poor in all GA6 and GC2 simulations. To assess how well the MetUM simulates spatial patterns of temporally coherent precipitation, empirical orthogonal teleconnection (EOT) analysis is applied to pentad-mean precipitation. Patterns are connected to large-scale processes by regressing atmospheric fields onto the EOT pentad timeseries. Most observed patterns of intraseasonal rainfall variability are found in all simulations, including the associated observed mechanisms. This suggests that GA6 and GC2 may provide useful predictions of summer intraseasonal variability, despite their substantial biases in mean precipitation and overall intraseasonal variance
Citation: Stephan, C. C., Klingaman, N. P., Vidale, P. L., Turner, A. G., Demory, M.-E., and Guo, L.: Intraseasonal summer rainfall variability over China in the MetUM GA6 and GC2 configurations, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-38, in review, 2018.
Claudia Christine Stephan et al.
Claudia Christine Stephan et al.
Claudia Christine Stephan et al.

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