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Robert Wood

maintains the cloud layer (e.g., Nicholls 1984 ; Bretherton and Wyant 1997 ), and controls the development of mesoscale organization ( Shao and Randall 1996 ; Atkinson and Zhang 1996 ; Jonker et al. 1999 ; de Roode et al. 2004 ). Latent heating in the upward branches of the convective elements and evaporation in downdrafts, provides an additional source of turbulence that strengthens the convection (e.g., Moeng et al. 1992 ). Thus, stratocumulus clouds frequently exert first-order effects upon

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Roland A. Madden and Paul R. Julian

effects in the extratropics, atmospheric angular momentum changes, and effects inthe ocean. Active workers in the field will find nothingnew in this review. We hope that it will bring thosewho want a general knowledge of the oscillation up todate. The review deals only with observational studies.We have, for the most part, neglected a considerablebody of theoretical and modeling work aimed at explaining the oscillation.2. Back~und In the late 1960s tropical data were sparse, as theystill are in

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Dayton G. Vincent

, structure, and characteristics of theSPCZ are described, with attention devoted to seasonal Corresponding author address: Dr. Dayton G. Vincent, Department of Earth and Atmospheric Sciences, Purdue University, 1397Civil Engineering Building, West Lafayette, IN 47907.c 1994 American Meteorological Societychanges. This is followed by a summary of theories andobservations concerning its origin and maintenance(section 3). Next, the significance of the SPCZ and itsrole within global-scale circulation

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Clark Evans, Kimberly M. Wood, Sim D. Aberson, Heather M. Archambault, Shawn M. Milrad, Lance F. Bosart, Kristen L. Corbosiero, Christopher A. Davis, João R. Dias Pinto, James Doyle, Chris Fogarty, Thomas J. Galarneau Jr., Christian M. Grams, Kyle S. Griffin, John Gyakum, Robert E. Hart, Naoko Kitabatake, Hilke S. Lentink, Ron McTaggart-Cowan, William Perrie, Julian F. D. Quinting, Carolyn A. Reynolds, Michael Riemer, Elizabeth A. Ritchie, Yujuan Sun, and Fuqing Zhang

companion article (Keller et al. 2018, manuscript submitted to Mon. Wea. Rev ., hereafter Part II) covers research progress related to ET’s downstream impacts, including downstream cyclogenesis, cyclone evolution after becoming extratropical, effects on the midlatitude flow and predictability, and phenomena such as predecessor rain events. 2. Classifiers Jones et al. (2003) discussed the need to develop improved conceptual models of, and diagnostic tools for, ET, with a particular focus toward the

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David M. Schultz and Philip N. Schumacher

–141. ——, and M. K. Yau, 1993: Assessment of slantwise convection in ERICA cyclones. Mon. Wea. Rev., 121, 375–386. ——, and N. Aktary, 1995: Convective and symmetric instabilities and their effects on precipitation: Seasonal variations in central Alberta during 1990 and 1991. Mon. Wea. Rev., 123, 153–162. ——, and R. Beaubien, 1996: Radar observations of snow formation in a warm pre-frontal snowband. Atmos.–Ocean, 34, 605

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T. N. Krishnamurti

from Indonesia to thefoothills of the Himalayas, from the (northern) winterto the (northern) summer season. The reverse motionensues in the following months. Along this axis, regionsof maximum rainfall totals of the order of 300-500mm/month can be followed as they migrate polewardand equatorward seasonally. Although the interannualvariability along this axis is quite large, this can beidentified as a principal axis of the monsoon. The largestheat source of the monsoon is associated with

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Markus Gross, Hui Wan, Philip J. Rasch, Peter M. Caldwell, David L. Williamson, Daniel Klocke, Christiane Jablonowski, Diana R. Thatcher, Nigel Wood, Mike Cullen, Bob Beare, Martin Willett, Florian Lemarié, Eric Blayo, Sylvie Malardel, Piet Termonia, Almut Gassmann, Peter H. Lauritzen, Hans Johansen, Colin M. Zarzycki, Koichi Sakaguchi, and Ruby Leung

evaluate the tendency terms for each process and to combine their effects to advance the discrete solution in time. The two most popular methods of splitting in operational models are sequential and parallel splitting. In sequential splitting, tendencies of the explicit processes are computed first and are used as input to the subsequent implicit fast process. Sequential splitting is in contrast to parallel splitting, where tendencies of all the parameterized processes are computed independently of

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

conservation of mass and circulation within a PV isoline on an isentropic surface. The computation of the MLM results in a stronger background flow than the climatological time average and, hence, stronger PV gradients. If one transcends linear theory and accounts for nonlinear effects, the waves do have an impact on the background state. In practice it may, therefore, be an advantage to use a nonstationary background flow, which implicitly accounts for the feedback of the waves on the waveguide. For

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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

research on the representation of model errors arising from diabatic processes using techniques such as stochastic physics. The research summarized in this review primarily focused on assessing the impact of ET on the short-to-medium-range forecast horizon. Preliminary results reveal a statistically significant correlation between monthly mean values of selected teleconnection indices and ET event counts, as well as significant departures from climatology on the subseasonal to seasonal time scale in

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Zhiyong Meng and Fuqing Zhang

heterogeneous distribution, and the related determination of the radius of influence. Radar radial velocity has been shown to have more of a positive impact than reflectivity. Some special or synthetic observations such as vortex position/intensity/size have also been found to have apparent positive effects on the performance of the LAM EnKF. The presence of model errors can often result in a large bias of the ensemble mean and too little spread, which can ultimately cause the ensemble forecast to fail

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