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B. Timbal, R. Kounkou, and G. A. Mills

1. Introduction Extreme weather events are often the most important aspect of the climate system felt by society and the natural environment; understanding the impact of any modification of the climate system on extreme events is therefore of the utmost importance. The Fourth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC; Solomon et al. 2007 ) has put a critical emphasis on the modification of the extreme climate events resulting from anthropogenic forcings. In

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Barry D. Keim and James F. Cruise

1990 over a 76.2-mm threshold recorded at Covington, Louisiana ( Keim 1996 ). Data can also be truncated on other criteria such as exceedences of two or three standard deviations ( Ratcliffe et al. 1978 ) or by partial duration series, among others. With the Covington storm data, trends are investigated after partitioning the data into three synoptic weather types; fronts, tropical disturbances, and air masses. Use of this classification scheme for storms is well documented in the literature (i

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John W. Kidson and Craig S. Thompson

models nested within a GCM. Statistical techniques have their origin in the model output statistics (MOS) and “perfect prog” approaches to forecasting surface weather elements (e.g., Klein 1982 ; Glahn 1985 ). They include the use of regression analysis (e.g., Kim et al. 1984 ; Klein and Bloom 1989 ; Karl et al. 1990 ; Hewitson 1994 ), canonical correlations ( von Storch et al. 1993 ), and neural networks ( Hewitson 1997 ). While correlation techniques may be appropriate to continuous variables

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Matthew J. Bunkers, James R. Miller Jr., and Arthur T. DeGaetano

130 JOURNAL OF CLIMATE VOLUME 9Definition of Climate Regions in the Northern Plains Using an Objective Cluster Modification Technique MAam-mw I. BcrtOmRS* AND JAMES R. MILLER JR.Institute of Atmospheric Sciences, South Dakota School of Mines and Technology, Rapid City, South Dakota ARTHUR T. DEGAETANONortheast Regional Climate Center, Cornell

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F. Justino and W. R. Peltier

variability of present-day surface climate conditions has been increasingly explored in several publications (e.g., Wang et al. 2005 ; Rodwell et al. 1999 ; Rogers 1990 ; Wallace and Gutzler 1981 ). According to Thompson and Wallace (2001) , the AO affects not only mean conditions but also the day-to-day variability of the weather regime, modulating the intensity of midlatitude storms and the frequency of occurrence of high-latitude blocking and cold-air outbreaks throughout the NH. Observation

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Matthew Collins

1. Introduction The El Niño–Southern Oscillation [ENSO; see, e.g., Philander (1990) ] is the largest mode of interannual variability of the global climate system. It arises from a dynamical interaction of the ocean and atmosphere in the equatorial Pacific and it impacts the weather and climate both locally and via teleconnections to remote areas. In this study we examine the interannual ENSO-like variability in the second Hadley Centre coupled climate model (HadCM2). The goals of the study are

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Donald R. Johnson and Akio Arakawa

undoubtedly be recognizedas one of a very few true pioneers in the developmentof global circulation models. With global circulationmodels now being a centerpiece of atmosphere sciencein both research and applications--medium- and longrange weather prediction models, atmospheric climatemodels, coupled atmospheric-ocean climate models,earth system models, planetary circulation models, atmospheric chemistry models, upper-atmosphere models, solar models, etc.--the entire scientific communityinvolved in

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Hollis E. Pyatt, Bruce A. Albrecht, Chris Fairall, J. E. Hare, Nicholas Bond, Patrick Minnis, and J. Kirk Ayers

Imager (TMI) satellite estimates of SST for 14–16 November 1999; both the cold tongue and strong SST gradient or equatorial front are quite distinct. As the MABL is advected from the cooler waters of the cold tongue across the equatorial front toward warmer waters, the structure of the boundary layer changes dramatically. Clouds such as fair-weather cumulus and stratocumulus are often present in the MABL with general increases in cloudiness on the warm side of the equatorial front ( Deser et al. 1993

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Mateusz Taszarek, John Allen, Tomáš Púčik, Pieter Groenemeijer, Bartosz Czernecki, Leszek Kolendowicz, Kostas Lagouvardos, Vasiliki Kotroni, and Wolfgang Schulz

1. Introduction Thunderstorms, particularly severe events accompanied by large hail, damaging wind gusts, tornadoes, or flash floods, pose a considerable risk to society ( Brooks 2013 ; Papagiannaki et al. 2013 ; Terti et al. 2017 ; Papagiannaki et al. 2017 ). Therefore, knowledge of their local climatology is not only important for weather forecasting purposes, but also for risk assessment by emergency managers or the (re)insurance industry. Another pressing question is whether such

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K. E. Runnalls and T. R. Oke

identical in every respect, R should be close to unity. However, if the environment of one station changes relative to the other, in such a way as to differentially affect T ma x and T min , values of R increasingly different from unity are to be expected. This is particularly so when weather or surface conditions enhance spatial variations in nocturnal cooling and therefore temperature. The most favorable weather occurs when skies are cloudless and winds are weak or calm. For the purposes of

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