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Andrew E. Mercer and Michael B. Richman

were similar in track density (number of storms per spatial unit) and therefore, no particular one is superior. Thus, NCEP–NCAR reanalysis data was selected for the raw variable extraction since it was used for creation of the CDC storm track dataset. Raw variables were extracted from the dataset at numerous pressure levels on a 2.5° latitude–longitude grid for most of North America. According to Kalnay et al. (1996) , the reanalysis dataset can be divided into several classes based on the

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Kirien Whan, Francis Zwiers, and Jana Sillmann

2012 ) and downstream ( Carrera et al. 2004 ; Favre and Gershunov 2006 ; Casola and Wallace 2007 ) impacts on North American temperatures, associated with either changes in the radiative balance or cold air advection, respectively ( Pfahl and Wernli 2012 ). Warm extremes are associated with collocated blocking events, while blocking has an influence on remote cold minimum temperature anomalies ( Carrera et al. 2004 ; Favre and Gershunov 2006 ; Casola and Wallace 2007 ; Pfahl and Wernli 2012

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Andrew G. Slater

North America there is a relatively high density of radiosondes for assimilation. AOD was derived from the MISR sensor (MISR_AM1_CGAS F15_0031, MIL3MAE; https://eosweb.larc.nasa.gov/project/misr/cgas_table ). The MISR product is a monthly optical depth with data from February 2000 through present. Missing values occur in this dataset; thus, each month missing MISR values are first filled on a spatial basis via Cressman (1959) weighting of neighboring grid cells within 90 km. From March 2003

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Michelle Hallack-Alegria and David W. Watkins Jr.

North American monsoon (NAM), occurring in the summer (July–September). The NAM is the northernmost portion of a more extensive region of heavy precipitation that first develops over southern Mexico during the spring and then spreads northward along the western slopes of the Sierra Madre Occidental ( Douglas et al. 1993 ; Stensrud et al. 1995 ). The monsoon circulation brings warm, humid air from the south, and short-lived thunderstorms result from convection as the air is lifted by orographic

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Steven M. Quiring and Daria B. Kluver

circulation patterns and precipitation ( Barnett et al. 1989 ; Dickson 1984 ; Garnett and Khandekar 1992 ; Hahn and Shukla 1976 ; Khandekar 1991 ). Numerous studies have demonstrated that Eurasian/Tibetan snow cover influences Indian/Asian monsoonal circulation and precipitation ( Fasullo 2004 ; Kripalani et al. 2002 ; Robock et al. 2003 ; Wu and Qian 2003 ; Zhang et al. 2004 ). Snow cover and snow water equivalent have also been linked to variability in the North American monsoon ( Ellis and

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Chunmei Zhu and Dennis P. Lettenmaier

1. Background Northwestern Mexico, a region that is strongly affected by the North American monsoon system (NAMS), receives between 60% and 80% of its annual precipitation during the June–September (JJAS) monsoon season ( Douglas et al. 1993 ). Understanding the genesis of warm season rainfall in northwestern Mexico has strong implications for warm season precipitation predictability over the NAMS region as well as much of the southern tier of U.S. states (which effectively are the northwestern

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Jessica K. Turner, John Gyakum, and Shawn M. Milrad

sounding, to simulate the formation of arctic air. Emanuel (2008) showed that the rate and depth of the cooling were sensitive to the amount of water vapor, condensate, and clouds. When clouds were allowed to form, air in contact with the cloud top cooled through radiation, while warming the lower layers through radiation and latent heat release. High-latitude northwestern North America is observed to be warming, especially during the winter season ( Jones and Moberg 2003 ; Serreze and Francis 2006

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Zhuo Wang, C-P. Chang, and Bin Wang

1. Introduction How the El Niño–Southern Oscillation (ENSO) impacts the North American climate during boreal summer has been explored in many previous studies but remains a controversial topic. For instance, Namias (1991) found that the composite 700-hPa geopotential height pattern during La Niña events has small perturbations over North America, and Adams and Comrie (1997) concluded that the interannual variability of the North America monsoon (NAM) is not strongly linked to El Niño. On

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John E. Janowiak, Valery J. Dagostaro, Vernon E. Kousky, and Robert J. Joyce

behavior such as the nighttime maxima over the central United States and over parts of central South America that are associated with low-level jet streams and orographic features. The main purpose of this paper addresses the second concern and thus we present an evaluation of the ability of the National Oceanic and Atmospheric Administration’s (NOAA) Global Forecast System model (GFS) and the regional Eta Model [currently referred to as the North American Mesoscale model (NAM)] to characterize the

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Richard Seager, Neil Pederson, Yochanan Kushnir, Jennifer Nakamura, and Stephanie Jurburg

Surface Temperature analysis (HadISST) ( Rayner et al. 2003 ). To examine if the 1960s drought and subsequent wetting can be reproduced as an atmospheric response to global SST variations we have examined a number of ensemble simulations with atmospheric general circulation models (GCMs) forced by historical SSTs. These include three models developed by NCAR, the Community Climate Model 3 [CCM3, which has been used extensively by us for North American drought research (e.g., Seager et al. 2005b

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