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Dudley B. Chelton and Craig M. Risien

geographical patterns of precipitation anomalies on time scales ranging from monthly to interannual in six regions along the west coast of North America. The PDSI ( Palmer 1965 ; Alley 1984 ) and MCDI ( Williams et al. 2017 ) incorporate the effects of precipitation, evapotranspiration, and runoff. Their use for studies of geographical patterns of drought variability is limited by the fact that they capture a single “intrinsic” time scale of long-term drought variability that varies from region to region

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Brian A. Colle and Michael E. Charles

1. Introduction a. Background This paper is the third in a series verifying extratropical cyclones within the operational models at the National Centers for Environmental Prediction (NCEP). In Parts I and II of this study, Charles and Colle (2009a , b , hereafter referred to as CC09a and CC09b) highlighted the performance of the North American Mesoscale (NAM), Global Forecast System (GFS), and Short-Range Ensemble Forecast (SREF) models around North America and its adjacent oceans for the

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Jinwon Kim, Duane E. Waliser, Chris A. Mattmann, Linda O. Mearns, Cameron E. Goodale, Andrew F. Hart, Dan J. Crichton, Seth McGinnis, Huikyo Lee, Paul C. Loikith, and Maziyar Boustani

and projection resource for the assessment of the climate change impact over most of North America. Table 1. The RCMs and corresponding references evaluated in this study. Surface insolation data from MM5I were not yet available at the time of writing. NARCCAP is composed of a set of RCM simulations using the large-scale forcing data from an atmospheric reanalysis (climate hindcast) and GCMs (climate scenarios) over a domain covering the North America region including Canada, the conterminous

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V. Isaac and W. A. van Wijngaarden

located in the Arctic where climate change effects should be most evident ( Solomon et al. 2007 ; van Wijngaarden 2008 ). The time period of 1948–2010 includes several decades when satellite observations were not available. Data were first checked for inhomogeneities before trends were computed. The extended time period of this study facilitated testing whether the trends were statistically significant. Finally, the seasonal trends are plotted to show which regions of North America have been most

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Sanjiv Kumar, James Kinter III, Paul A. Dirmeyer, Zaitao Pan, and Jennifer Adams

evaluate the CMIP5 climate models’ skill in simulating the observed twentieth-century warming hole in North America, 2) to determine the relationship between observed temperature variability and natural multidecadal climate variability, and 3) to assess the twenty-first century warming hole projections in view of the twentieth-century warming hole’s simulation uncertainty. Section 2 describes CMIP5 data used and the methods applied. Results are given in section 3 , and section 4 presents a summary

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Toby R. Ault, Julia E. Cole, Jonathan T. Overpeck, Gregory T. Pederson, Scott St. George, Bette Otto-Bliesner, Connie A. Woodhouse, and Clara Deser

1. Introduction In western North America (WNA), the term “megadrought” typically refers to an interval of aridity in the past that is more prolonged than anything seen during the twentieth century ( Woodhouse and Overpeck 1998 ; Cook et al. 1999 , 2004 ; Stahle et al. 2007 ; Meko et al. 2007 ; Cook et al. 2010 ). If such an event were to occur in the future, it would likely put unprecedented strains on existing water resources. Understanding megadrought risk is therefore critical to

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Thang M. Luong, Christopher L. Castro, Hsin-I Chang, Timothy Lahmers, David K. Adams, and Carlos A. Ochoa-Moya

upward trend ( Kunkel et al. 2013 ). Any long-term increases in precipitation intensity should be most apparent during the North American monsoon (NAM; Adams and Comrie 1997 ) in late summer (July–early September) because this is the period of warm-season severe weather caused by convective thunderstorms. There is observational evidence to suggest that monsoon precipitation is becoming more extreme in the Southwest and in northwestern Mexico (e.g., Anderson et al. 2010 ; Petrie et al. 2014

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Bruce T. Anderson, Alex C. Ruane, John O. Roads, and Masao Kanamitsu

1. Introduction North America is one of the best meteorologically and climatologically monitored regions in the world, and its distinct regional characteristics make it an ideal test bed for hydrometeorological analyses. One of the earliest to look at atmospheric hydrologic balances across the region was Rasmusson (1968) . Since then, major hydroclimatic studies of the region include the Global Energy and Water Cycle Experiment (GEWEX) Americas Prediction Project (GAPP) over the Mississippi

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Patrick Grenier

(metrics) employed to investigate the PI problem. Section 3 presents the results, which are interpreted in Section 4 . Section 5 consists of a summary with concluding remarks. The appendix contains the list of acronyms used in the paper. 2. Data and methods a. Study sites The study is conducted for 12 sites (cities) over North America (see Table 1 and Fig. 1 ). Each site is identified with coordinates of a station from the World Meteorological Organization (WMO) network, but the reference

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Eric Holt and Jun Wang

found a declining trend in surface wind speed over the last five decades in many parts of the world (as summarized in Table 1 ), including Australia ( Roderick et al. 2007 ; McVicar et al. 2008 ), China ( Xu et al. 2006a , b ), Europe ( Pirazzoli and Tomasin 2003 ), and North America ( Klink 1999 ; Tuller 2004 ; Pryor et al. 2007 ; Hundecha et al. 2008 ). Over the United States, Pryor et al. (2009) found a 0.84 ± 0.32 m s −1 decrease in the 90th-percentile 10-m winds from 1973 to 2005. Table

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