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J. David Neelin, Baird Langenbrunner, Joyce E. Meyerson, Alex Hall, and Neil Berg

large scale, there tends to be increasing confidence in the representation of climate features in the global models, especially in terms of physical pathway. Thus in asking whether there is any basis for regarding the changes in this region in CMIP5 models as significant, we move from point-by-point assessment to examination of a relatively large-scale precipitation pattern associated with storm-track changes and the relationship of this to changes in the eastern Pacific subtropical jet. In this

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Justin Sheffield, Andrew P. Barrett, Brian Colle, D. Nelun Fernando, Rong Fu, Kerrie L. Geil, Qi Hu, Jim Kinter, Sanjiv Kumar, Baird Langenbrunner, Kelly Lombardo, Lindsey N. Long, Eric Maloney, Annarita Mariotti, Joyce E. Meyerson, Kingtse C. Mo, J. David Neelin, Sumant Nigam, Zaitao Pan, Tong Ren, Alfredo Ruiz-Barradas, Yolande L. Serra, Anji Seth, Jeanne M. Thibeault, Julienne C. Stroeve, Ze Yang, and Lei Yin

surface temperatures, and atmospheric and surface water budgets. Section 4 evaluates the model simulations of extremes of temperature and surface hydrology and temperature-based biophysical indicators such as growing season length. Section 5 focuses on regional climate features such as North Atlantic winter storms, the Great Plains low-level jet, and Arctic sea ice. The results are synthesized in section 6 and compared to results from CMIP3 models for selected variables. 2. CMIP5 models and

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Brian A. Colle, Zhenhai Zhang, Kelly A. Lombardo, Edmund Chang, Ping Liu, and Minghua Zhang

explain the cyclone differences, such as low-level temperature gradients and the upper-level jet? Is there any indication of future cyclone change in terms of frequency, intensity, or spatial distribution? 2. Data and methods The Climate Forecast System Reanalysis (CFSR; Saha et al. 2010 ) at ~38-km grid spacing (64 vertical levels) was used to verify and compare the cyclone properties with the CMIP5 models for a few domains [East Coast land (ECL), East Coast water (ECW), and East Coast western and

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Zaitao Pan, Xiaodong Liu, Sanjiv Kumar, Zhiqiu Gao, and James Kinter

processes by reconciling the temperature difference between upper-air and surface observations. Combining observations with a regional climate model's results, Pan et al. (2004) suggested that regional hydrological processes coupled with the low-level jet contribute to the cooling. Other studies have attributed the cooling to the internal dynamics ( Kunkel et al. 2006 ; Liang et al. 2006 ; Weaver 2013 ). A number of modeling studies have attributed the mechanisms for this abnormal trend to large

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Jeanne M. Thibeault and Anji Seth

; Weaver and Nigam 2008 ). Variations in NASH extent and strength determine the strength of the Great Plains low-level jet (GPLLJ) that transports moisture into central and eastern North America ( Wang 2007 ; Mestas-Nunez and Enfield 2007 ; Wang et al. 2007 ). Li et al. (2011) suggest that the recent observed increased variability in the southeastern U.S. (SE) summer precipitation is related to increased intensity of the NASH, accompanied by a westward shift of its western ridge. On interannual

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

variability (ISV) during boreal summer (e.g., Knutson and Weickmann 1987 ; Kayano and Kousky 1999 ; Maloney and Hartmann 2000a ; Maloney and Esbensen 2003 , 2007 ; de Szoeke and Bretherton 2005 ; Jiang and Waliser 2008 , 2009 ; Jiang et al. 2011 ). ISV over the EP exerts broad impacts on regional weather and climate phenomena, including tropical cyclone activity over the EP and the Gulf of Mexico, the summertime gap wind near the Gulfs of Tehuantepec and Papagayo, the Caribbean low-level jet and

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Kerrie L. Geil, Yolande L. Serra, and Xubin Zeng

1. Introduction The evolution of the North American monsoon system (NAMS) can be described as having development, mature, and decay stages similar to but less intense than its larger Asian counterpart. During the development stage (May–June), the extratropical jet weakens and migrates to the north resulting in decreased frequency of synoptic-scale transient activity from the midlatitudes over northern Mexico and the southwestern United States ( Higgins et al. 1997 ). A thermal surface low forms

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Eric D. Maloney, Suzana J. Camargo, Edmund Chang, Brian Colle, Rong Fu, Kerrie L. Geil, Qi Hu, Xianan Jiang, Nathaniel Johnson, Kristopher B. Karnauskas, James Kinter, Benjamin Kirtman, Sanjiv Kumar, Baird Langenbrunner, Kelly Lombardo, Lindsey N. Long, Annarita Mariotti, Joyce E. Meyerson, Kingtse C. Mo, J. David Neelin, Zaitao Pan, Richard Seager, Yolande Serra, Anji Seth, Justin Sheffield, Julienne Stroeve, Jeanne Thibeault, Shang-Ping Xie, Chunzai Wang, Bruce Wyman, and Ming Zhao

exceeding 95% at points seen in Fig. 2 . High interannual variance over coastal land points prevents these from passing the stricter Neelin et al. (2006) criterion. Area averages pass significance tests on the model ensemble ( Neelin et al. 2013 ), which points out a relationship between the extension of storm-track-associated precipitation in this region and the regional manifestation of jet stream increases at the steering level. For such differences at the boundaries of precipitation features, it

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Xianan Jiang, Eric D. Maloney, Jui-Lin F. Li, and Duane E. Waliser

1. Introduction During boreal summer, convective activity over the eastern North Pacific Ocean (ENP) along the intertropical convergence zone (ITCZ) exhibits significant intraseasonal variability (ISV). Through its associated large-scale circulation and thermodynamical variations, the ISV exerts broad impacts on regional weather and climate systems, including the North American monsoon (NAM), midsummer drought over Central America, and Caribbean rainfall and low-level jet, as well as tropical

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Edmund K. M. Chang

storm-track latitude tend to project larger poleward shifts [similar to the relationship found by Kidson and Gerber (2010) for the Southern Hemisphere eddy-driven jet]. In those cases, one may argue that bias corrections to model projections can be developed based on the relationship between model biases and future projections ( Chang et al. 2012 ; Kidson and Gerber 2010 ). We have examined whether the strength of a model’s climatological storm track (as indicated by pp) is correlated with the

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