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David K. Adams and Andrew C. Comrie

The North American monsoon is an important feature of the atmospheric circulation over the continent, with a research literature that dates back almost 100 years. The authors review the wide range of past and current research dealing with the meteorological and climatological aspects of the North American monsoon, highlighting historical development and major research themes. The domain of the North American monsoon is large, extending over much of the western United States from its region of greatest influence in northwestern Mexico. Regarding the debate over moisture source regions and water vapor advection into southwestern North America, there is general agreement that the bulk of monsoon moisture is advected at low levels from the eastern tropical Pacific Ocean and the Gulf of California, while the Gulf of Mexico may contribute some upper-level moisture (although mixing occurs over the Sierra Madre Occidental). Surges of low-level moisture from the Gulf of California are a significant part of intraseasonal monsoon variability, and they are associated with the configuration of upper-level midlatitude troughs and tropical easterly waves at the synoptic scale, as well as the presence of low-level jets, a thermal low, and associated dynamics (including the important effects of local topography) at the mesoscale. Seasonally, the gulf surges and the latitudinal position of the midtropospheric subtropical ridge over southwestern North America appear to be responsible for much spatial and temporal variability in precipitation. Interannual variability of the North American monsoon system is high, but it is not strongly linked to El Niño or other common sources of interannual circulation variability. Recent mesoscale field measurements gathered during the South-West Area Monsoon Project have highlighted the complex nature of the monsoon-related severe storm environment and associated difficulties in modeling and forecasting.

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Yolande L. Serra, David K. Adams, Carlos Minjarez-Sosa, James M. Moker Jr., Avelino F. Arellano, Christopher L. Castro, Arturo I. Quintanar, Luis Alatorre, Alfredo Granados, G. Esteban Vazquez, Kirk Holub, and C. DeMets

Expanding networks of all-weather, high-time-resolution GPS networks with surface meteorology throughout the southwestern United States and Mexico offers opportunities for improved understanding of the North American monsoon convection and forecasting of organized convective events and associated hazards. The North American monsoon accounts for more than half of the total annual precipitation over northwestern Mexico ( Adams and Comrie 1997 ) and is important to agriculture and water resources

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Steven M. Quiring, Trent W. Ford, Jessica K. Wang, Angela Khong, Elizabeth Harris, Terra Lindgren, Daniel W. Goldberg, and Zhongxia Li

et al. 2013 ), and the onset and location of afternoon convective precipitation ( Findell et al. 2011 ; Taylor et al. 2012 ). Soil moisture is used for drought monitoring and in drought early warning systems in Asia ( Wang et al. 2011 ; Tei et al. 2013 ), Africa ( Anderson et al. 2012 ; Yuan et al. 2013 ), Australia ( Cai et al. 2009 ), Europe ( Zampieri et al. 2009 ; Mozny et al. 2012 ), North America ( Tang and Piechota 2009 ; Bolten et al. 2010 ), and South America ( Markewitz et al. 2010

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Fedor Mesinger, Geoff DiMego, Eugenia Kalnay, Kenneth Mitchell, Perry C. Shafran, Wesley Ebisuzaki, Dušan Jović, Jack Woollen, Eric Rogers, Ernesto H. Berbery, Michael B. Ek, Yun Fan, Robert Grumbine, Wayne Higgins, Hong Li, Ying Lin, Geoff Manikin, David Parrish, and Wei Shi

In 1997, during the late stages of production of NCEP–NCAR Global Reanalysis (GR), exploration of a regional reanalysis project was suggested by the GR project's Advisory Committee, “particularly if the RDAS [Regional Data Assimilation System] is significantly better than the global reanalysis at capturing the regional hydrological cycle, the diurnal cycle and other important features of weather and climate variability.” Following a 6-yr development and production effort, NCEP's North American Regional Reanalysis (NARR) project was completed in 2004, and data are now available to the scientific community. Along with the use of the NCEP Eta model and its Data Assimilation System (at 32-km–45-layer resolution with 3-hourly output), the hallmarks of the NARR are the incorporation of hourly assimilation of precipitation, which leverages a comprehensive precipitation analysis effort, the use of a recent version of the Noah land surface model, and the use of numerous other datasets that are additional or improved compared to the GR. Following the practice applied to NCEP's GR, the 25-yr NARR retrospective production period (1979–2003) is augmented by the construction and daily execution of a system for near-real-time continuation of the NARR, known as the Regional Climate Data Assimilation System (R-CDAS). Highlights of the NARR results are presented: precipitation over the continental United States (CONUS), which is seen to be very near the ingested analyzed precipitation; fits of tropospheric temperatures and winds to rawinsonde observations; and fits of 2-m temperatures and 10-m winds to surface station observations. The aforementioned fits are compared to those of the NCEP–Department of Energy (DOE) Global Reanalysis (GR2). Not only have the expectations cited above been fully met, but very substantial improvements in the accuracy of temperatures and winds compared to that of GR2 are achieved throughout the troposphere. Finally, the numerous datasets produced are outlined and information is provided on the data archiving and present data availability.

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James A. Screen, Clara Deser, and Lantao Sun

Contrary to recent claims, North American cold extremes are expected to become less frequent as a result of continuing Arctic sea ice loss. In early January 2014, an Arctic air outbreak brought extreme cold to central and eastern North America. Record low minimum temperatures for the calendar date were set at many weather stations, including at Chicago, Illinois (O’Hare Airport, –26.7°C/–16°F, 6 January); New York, New York (Central Park, –15.6°C/4°F, 7 January); Washington, D.C. (Dulles

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D. J. Mullan, I. D. Barr, R. P. Flood, J. M. Galloway, A. M. W. Newton, and G. T. Swindles

that influence the development of lake ice ( Dibike et al. 2012 ). Given this limitation, the present study applies—for the first time—a process-based freshwater lake model to simulate the impacts of climate change on winter roads. We do this by examining the future viability of the world’s busiest heavy-haul winter road to GMTIs of 1.5°, 2°, and 4°C above preindustrial temperatures. We also make inferences for the future viability of other winter roads across Arctic North America based on

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Cara L. Cuite, Rebecca E. Morss, Julie L. Demuth, and William K. Hallman

classification scheme for winter storms in the eastern and central United States with an emphasis on “nor’easters .” Bull. Amer. Meteor. Soc. , 83 , 37 – 51 ,<0037:ACSFWS>2.3.CO;2 . 10.1175/1520-0477(2002)083<0037:ACSFWS>2.3.CO;2 1 A nor’easter, also called a northeaster or northeast storm, is a “cyclonic storm of the east coast of North America, so called because the winds over the coastal area are from the northeast” ( American Meteorological Society 2020

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Linda O. Mearns, Ray Arritt, Sébastien Biner, Melissa S. Bukovsky, Seth McGinnis, Stephan Sain, Daniel Caya, James Correia Jr., Dave Flory, William Gutowski, Eugene S. Takle, Richard Jones, Ruby Leung, Wilfran Moufouma-Okia, Larry McDaniel, Ana M. B. Nunes, Yun Qian, John Roads, Lisa Sloan, and Mark Snyder

moved forward to systematically examine the combined uncertainty in future climate projections from global and regional models ( Christensen et al. 2007b Christensen et al. 2009 ), but no such research program has heretofore been developed over North America (NA). We developed the North American Regional Climate Change Assessment Program (NARCCAP) ( Mearns et al. 2009 ) to fill this research gap. The fundamental scientific motivation of NARCCAP is to explore the separate and combined uncertainties

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Andreas Hamann, Tongli Wang, David L. Spittlehouse, and Trevor Q. Murdock

to use for researchers and resource managers. We address this need for climatically characterizing sample data, extracting custom time series, and generating high-resolution gridded data with a software solution that allows for custom queries and downscaling of historical and future climate data for western North America. We use climate data for the 1961–90 normal period, developed with the Parameter-elevation Regressions on Independent Slopes Model (PRISM). PRISM is an expert interpolation

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Kevin Hamilton

The problem of formulating optimal-regulation strategies for commercial fisheries is complicated by the large interannual fluctuations often observed in the numbers and locations of various fish populations. Much of the interannual variance seen in particular cases can be attributed to the effects of environmental variability. The article reviews three examples of research showing that environmental variations can have important systematic effects on fish stocks. The three examples are all from North America and have been chosen to illustrate the biological significance of meteorological and oceanographic phenomena on a wide range of space and time scales.

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