North American Climate in CMIP5 Experiments. Part II: Evaluation of 20th Century Intra-Seasonal to Decadal Variability

Justin Sheffield, Suzana J. Camargo, Rong Fu, Qi Hu, Xianan Jiang, Nathaniel Johnson, Kristopher B. Karnauskas, Jim Kinter, Sanjiv Kumar, Baird Langenbrunner, Eric Maloney, Annarita Mariotti, Joyce E. Meyerson, J. David Neelin, Zaitao Pan, Alfredo Ruiz-Barradas, Richard Seager, Yolande L. Serra, De-Zheng Sun, Chunzai Wang, Shang-Ping Xie, Jin-Yi Yu, Tao Zhang, Ming Zhao J. Climate, submitted 7/30/12.

Preprint (7 MB).


Abstract This is the second part of a three-part paper on North American climate in CMIP5 that evaluates the 20th simulations of intra-seasonal to multi-decadal variability and teleconnections with North American climate. Overall, the multi-model ensemble does reasonably well at reproducing observed variability in several aspects, but does less well at capturing observed teleconnections, with implications for future projections examined in part three of this paper. In terms of intra-seasonal variability, almost half of the models examined can reproduce observed variability in the eastern Pacific and most models capture the midsummer drought over Central America. The multi-model mean replicates the density of tropical disturbances and storms but with large spread among the models. The coarse resolution of the models means that tropical cyclone frequencies are under predicted in the Atlantic and eastern North Pacific. The frequency and mean amplitude of ENSO are generally well reproduced, although teleconnections with North American climate are widely varying among models and only a few models can reproduce the east and central Pacific types of ENSO and connections with US winter temperatures. The models capture the spatial pattern of PDO variability and its influence on continental temperature and West coast precipitation, but less well for the wintertime precipitation. The spatial representation of the AMO is reasonable but the magnitude of SST anomalies and teleconnections are poorly reproduced. Multi-decadal trends such as the warming hole over the central-southeast US and precipitation increases are not replicated by the models, indicating that observed changes are linked to natural variability.

Citation Sheffield, J. Et al,: North American Climate in CMIP5 Experiments. Part II: Evaluation of 20th Century Intra-Seasonal to Decadal Variability. J. Climate, submitted 7/30/12.

Acknowledgments. We acknowledge the World Climate Research Programme's Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output. For CMIP the U.S. Department of Energy's Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. The authors acknowledge the support of NOAA Climate Program Office Modeling, Analysis, Predictions and Projections (MAPP) Program as part of the CMIP5 Task Force.