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F. M. Ralph, T. Coleman, P. J. Neiman, R. J. Zamora, and M. D. Dettinger

1. Introduction Past studies have shown that atmospheric rivers (ARs), which are regions of the lower atmosphere characterized by strong winds and large water vapor contents (usually associated with a surface cold front in the midlatitudes), are key features of the global water cycle (e.g., Zhu and Newell 1998 ), are detectable in satellite observations (see example in Fig. 1a ) ( Ralph et al. 2004 ; Neiman et al. 2008a ), and are associated with heavy rain and flooding on the U.S. West

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F. M. Ralph, E. Sukovich, D. Reynolds, M. Dettinger, S. Weagle, W. Clark, and P. J. Neiman

precipitation events, the threat score tends to zero. In addition, the threat score does not distinguish the source of forecast error, making it difficult to identify causes of missed and/or falsely predicted events. A leading example of the demand to address extreme precipitation events comes from the hydrology–reservoir operations, flood control, and emergency management communities. Currently, all 13 of NOAA’s NWS River Forecast Centers (RFCs) in the United States ingest precipitation (both observed and

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Sandra E. Yuter, David A. Stark, Justin A. Crouch, M. Jordan Payne, and Brian A. Colle

the mountainous U.S. west coast. The more intense precipitation events are related to “atmospheric rivers” ( Zhu and Newell 1998 ), narrow plumes of moisture associated with fronts on oceanic cyclones ( Bao et al. 2006 ). These enhanced bands of vertically integrated water vapor typically form as the result of local moisture convergence ( Bao et al. 2006 ). Under a subset of environmental conditions, the moisture can be traced back from the U.S. west coast to the tropics ( Bao et al. 2006 ). These

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James A. Smith, Gabriele Villarini, and Mary Lynn Baeck

contributions of both tropical and extratropical systems. Counts per year of flood peaks in the Potomac have an index of dispersion (variance divided by the mean of annual counts) greater than 1 ( Fig. 3 ), suggesting that clustering may play an important role in the occurrence process of flood events. The flood of record for the Potomac River, as for many large drainages in the eastern United States and the Ohio River basin (see Miller 1990 ), occurred in March 1936. Miller (1990) presents the March

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Masamichi Ohba, Shinji Kadokura, Yoshikatsu Yoshida, Daisuke Nohara, and Yasushi Toyoda

, which is a high-impact weather system and plays an important role in water resources. Figure 1c shows the climatological June–July mean precipitation, which is represented by climatological monthly-mean rainfall obtained from CMAP. In the Yangtze River valley of China and central Japan, the baiu front commences in early boreal summer, during which a zonally elongated rainband covers China, Korea, Japan, and the northwestern Pacific along 30°–40°N ( Fig. 1c ). Research on the baiu front (e

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Xiaogu Zheng and Craig S. Thompson

catchment and to estimate this variability for the next two to three decades. To this end, a climate variable is needed that is both predictable and significantly associated with rainfall on a decadal time scale. Fortunately, the IPO may be such a climate variable. The IPO has significant impacts on rainfall and river flows in certain regions of New Zealand. In the west and south of South Island, the negative IPO phase is generally associated with lower rainfall and inflows, and vice versa for the

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Youcun Qi, Jian Zhang, Brian Kaney, Carrie Langston, and Kenneth Howard

coordinates . Quart. J. Roy. Meteor. Soc. , 139 , 2233 – 2240 , doi: 10.1002/qj.2095 . Qi, Y. , Zhang J. , Zhang P. , and Cao Q. , 2013c : VPR correction of bright band effects in radar QPEs using polarimetric radar observations . J. Geophys. Res. Atmos. , 118 , 3627 – 3633 , doi:10.1002/jgrd.50364 . Ralph, F. M. , Neiman P. J. , and Wick G. A. , 2004 : Satellite and CALJET aircraft observations of atmospheric rivers over the eastern North Pacific Ocean during the winter of 1997

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Jonathan J. Gourley, Scott E. Giangrande, Yang Hong, Zachary L. Flamig, Terry Schuur, and Jasper A. Vrugt

. , 29 , 855 – 861 . 10.1111/j.1752-1688.1993.tb03245.x Marselek, J. , 1981 : Calibration of the tipping-bucket raingage. J. Hydrol. , 53 , 343 – 354 . 10.1016/0022-1694(81)90010-X Nash, J. , and Sutcliffe J. , 1970 : River flow forecasting through conceptual models. Part I: A discussion of principles. J. Hydrol. , 10 , 282 – 290 . 10.1016/0022-1694(70)90255-6 NWS , cited . 2007 : NWS directives system. National Weather Service Instruction 10-1605. [Available online at http

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Jian Zhang and Youcun Qi

been under real-time evaluations at several river forecast centers. One of the issues found with the NMQ radar-based precipitation product is the overestimation of precipitation associated with bright band (BB). The bright band is a layer of enhanced reflectivity due to melting of aggregated snow ( Fig. 1 ). The phenomenon has been recognized near the beginning of radar meteorology (e.g., Ryde 1947 ; Austin and Bemis 1950 ; Wexler and Atlas 1956 ; Lhermitte and Atlas 1963 ), and many recent

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