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Yongxin Zhang, Valérie Dulière, Philip W. Mote, and Eric P. Salathé Jr.

1. Introduction The U.S. Pacific Northwest is characterized by mountainous terrain and intricate land–sea contrasts ( Fig. 1 ) resulting in a host of finescale weather systems such as sea and land breezes, rain shadows, and downslope windstorms that define the local weather and climate ( Mass 2008 ). In a warming climate, such finescale weather systems can significantly alter the local temperature and precipitation trends ( Salathé et al. 2008 ) and are essential to consider in climate

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David I. Duncan, Christian D. Kummerow, and Gregory S. Elsaesser

1. Introduction Clouds, precipitation, and their effects on the local environment are inextricably linked, yet are often treated separately. New paradigms that seek to exploit the relationship between cloud and precipitation states offer some hope to link the two disciplines. Studies that have endeavored to categorize “weather states” have approached the issue from the perspective of either classifying similar cloud states (e.g., Jakob and Tselioudis 2003 ; Rossow et al. 2005 ) or

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J. E. Kay, K. Raeder, A. Gettelman, and J. Anderson

describe and implement a physically motivated modification to the stratus cloud parameterization, requiring a well-mixed boundary layer for stratus clouds to be diagnosed. We then contrast the influence of stability-based cloud parameterizations on Arctic clouds in the forecasts and freely evolving CAM4 runs. In section 4 , we discuss the relevance of our findings for high-latitude climate feedbacks. We conclude with a summary of our most important findings in section 5 . 2. Model description and

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Delphine Texier, Nathalie de Noblet, and Pascale Braconnot

the magnitude of monsoon changes was underestimated by models ( Yu and Harrison 1996 ; Texier et al. 1997 ; Joussaume et al. 1999 ). These results suggest that the 6-kyr-BP orbital change alone is not sufficient to produce the observed climate change;internal feedbacks must then be accounted for. Numerical experiments have shown that African and Asian summer monsoons, at present as well as during the mid-Holocene, are sensitive to modifications in the land surface consequent to changes in 1

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D. Alex Burrows, Craig R. Ferguson, Matthew A. Campbell, Geng Xia, and Lance F. Bosart

1. Introduction The Great Plains (GP) low-level jet (LLJ) is the primary transport mechanism of moisture-laden air from the Gulf of Mexico into the GP and is essential to the region’s agricultural and wind energy sectors, hydroclimate, and severe weather regimes. Bonner (1968) first objectively defined the southerly GPLLJ based on its diurnal oscillation in speed, height, and direction. The GPLLJ has a well-defined corridor (Texas to South Dakota) with a diurnal cycle that peaks after local

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Roy Rasmussen, Changhai Liu, Kyoko Ikeda, David Gochis, David Yates, Fei Chen, Mukul Tewari, Michael Barlage, Jimy Dudhia, Wei Yu, Kathleen Miller, Kristi Arsenault, Vanda Grubišić, Greg Thompson, and Ethan Gutmann

simulations The Weather Research and Forecasting (WRF) regional weather and climate model version 3.0 ( Skamarock et al. 2005 ) was used for both the historical verification runs and the PGW simulations. The relevant model parameterizations included the Noah land surface model ( Chen and Dudhia 2001 ; Ek et al. 2003 ); Mellor–Yamada–Janjić (MYJ) planetary boundary layer scheme ( Skamarock et al. 2005 ); Community Atmosphere Model’s (CAM) longwave and shortwave schemes ( Collins et al. 2006 ); and

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Guomin Wang, Pandora Hope, Eun-Pa Lim, Harry H. Hendon, and Julie M Arblaster

1. Introduction Extreme weather and climate events are of great concern to the public, emergency services, industry, finance sectors, and policy makers. While there is strong evidence linking global-scale warming to the increases in anthropogenic greenhouse gas emissions ( Bindoff et al. 2013 ), there is increasing evidence that extreme heat and rainfall events are increasing as well. However, because of the smaller samples of extreme events, which by definition occur in the tails of

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Ole B. Christensen, Jens H. Christensen, Bennert Machenhauer, and Michael Botzet

of 19 km is driven by an RCM with a resolution of 57 km, which in turn is driven by a GCM that has a resolution of about 250 km (spectral T42). Experience from numerical weather prediction modeling shows that too big a difference in resolution between driving fields and an RCM gives numerical problems. Therefore the double nesting. We focus on the Scandinavian Peninsula where many finescale details in the topography are responsible for the local climate. At the high resolution used here, local

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John D. Horel, Judith B. Pechmann, John E. Geisler, and Andrea N. Hahmann

the 5-day simulations. The impacts on the simulated circulation of major changes to the s~andard MM4 are assessed. When animproved treatment of radiative processes is included, excessive rainfall develops over the Andes Mountainsand over the Amazon Basin. The excessive rainfall is concentrated in "gridpoint' storms that are not eliminatedwhen the surface physical parametefizations are improved. Modifications to the treatment of the vertical transpo~of moisture are required to diminish the

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Eric M. Wilcox

precipitation in CCM3 is a consequence of a tendency within the convective parameterization scheme to neutralize instability too frequently. Similarly, the complete dominance of convective precipitation over stable condensation results from the too frequent invocation of the convection scheme. A reformulation of the convective parameterization is beyond the scope of this paper. However, a simple modification to the parameterization of convective precipitation in the model is tested here that simulates the

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