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Robert D. Elliott

486JOURNAL OF METEOROLOGYVOLUME 15CALIFORNIA STORM CHARACTERISTICS AND WEATHER MODIFICATION By Robert D. Elliott North American Weather Consultants(Original manuscript received 20 January 1958 ; revised manuscript received 31 March 1958)ABSTRACTIn connection with cloud seeding projects in Pacific Coast states, detailed analyses have been preparedof many storms. From this material, average values of significant parameters have been computed and areemployed to

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Bart Geerts, Qun Miao, Yang Yang, Roy Rasmussen, and Daniel Breed

1. Introduction In a 2008 editorial column in Nature , it was argued that “… weather modification is one of those areas in which science can have an immediate and obvious benefit for society” ( Nature 2008 ). Cloud seeding probably has been the most widely practiced method of intentional weather modification for the last few decades (e.g., Bruintjes 1999 ; Qiu and Cressey 2008 ). It is remarkable that notwithstanding a series of targeted field campaigns and the stronger experimental control

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Edward N. Lorenz

altogether suitable. One such study is the problem of the appearance and growth of errors in routine weather forecasting when both analysis error and model error are present. Here, of course, we need one model—the “perfect” model—just to produce the simulated true states, and a “model error” will mean the failure of a simulated operational forecasting model to duplicate the perfect one. I shall note certain shortcomings of the original model for pursuing this problem and describe my attempts to redesign

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Elisa Spreitzer, Roman Attinger, Maxi Boettcher, Richard Forbes, Heini Wernli, and Hanna Joos

1. Introduction The dynamics of extratropical weather systems are substantially affected by heating and cooling due to diabatic processes, such as cloud latent heat release and radiative transfer, as well as by turbulent mixing and friction. This applies from the mesoscale to the large scale, including fronts (e.g., Parker and Thorpe 1995 ; Lackmann 2002 ; Igel and van den Heever 2014 ), cyclones (e.g., Stoelinga 1996 ; Rossa et al. 2000 ; Adamson et al. 2006 ), and Rossby waves (e

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Martin Leutbecher

observations and additionally obtain an estimate of the expected reduction of the magnitude of forecast error due to the use of the additional observations. Only with such an estimate is it actually possible to define the meaning of “optimal” sites for supplementary observations ( Berliner et al. 1999 ). In principle, changes of the forecast error covariance matrix due to modifications of the observing network could be evaluated with an extended Kalman filter. However, this is computationally not feasible

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Edward N. Lorenz

with trajectories inphase space. For those systems with bounded solutions, it is found that nonperiodie solutions are ordinarilyunstable with respect to small modifications, so that slightly differing initial states can evolve into considerably different states. Systems with bounded solutions are shown to possess bounded numerical solutions. A simple system representing cellular convection is solved numerically. All of tke solutions are foundto be unstable, and almost all of them are nonperiodic

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J. I. Metcalf and J. D. Echard

., and P. V. Hobbs, 1975: The use of a vertically pointing pulsed Doppler radar in cloud physics and weather modification studies. J. Appl. Meteor., 14, 222-231.

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T. E. Hoffer and J. A. Warburton

complete accord with diffusional growth. Thedifferences are discussed with respect to weather modification.1. Introduction There have been many investigations of the growth ofice crystals by diffusional process (Houghton, 1949).The growth characteristics have been calculated fromtheoretical considerations and demonstrated in laboratory studies. Ice crystals collected from natural cloudsoften exhibit single-crystal characteristics, but at othertimes show evidence of more complex growth formswhere

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Dominik Büeler and Stephan Pfahl

1. Introduction Extratropical cyclones are a key component of the global atmospheric circulation because of their transport of heat, moisture, and angular momentum ( Held 1975 ; Chang et al. 2002 ). They contribute substantially to the synoptic weather variability in the midlatitudes on a daily to weekly time scale. When reaching high intensities, they can cause extreme winds and heavy precipitation with a huge impact on society, which makes them the third-costliest natural disasters after

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Da-Lin Zhang and J. Michael Fritsch

Warner, ismodified to simulate the meso-0 scale structure and evolution of convectively driven weather systems. Themodifications include: (i) two-way interactive nested-grid procedures, (ii) the Fritsch-Chappell convective parameterization scheme, and (iii) the.Blackadar boundary layer package.An 18-h simulation of the Johinstown flood of July 1977 is conducted. Compared to the documentation ofHoxit et ai. and Bosart and Sanders, the simulation reproduced many of the different aspects of the

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