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Robert R. Gillies, Shih-Yu Wang, Jin-Ho Yoon, and Scott Weaver

– 2742 . 10.1175/1520-0469(1987)044<2727:RWLFDO>2.0.CO;2 Lau, N. C. , and Nath M. J. , 1999 : Observed and GCM-simulated westward-propagating, planetary-scale fluctuations with approximately three-week periods. Mon. Wea. Rev. , 127 , 2324 – 2345 . 10.1175/1520-0493(1999)127<2324:OAGSWP>2.0.CO;2 Madden, R. A. , and Julian P. R. , 2005 : Historical perspective. Intraseasonal Variability in the Atmosphere–Ocean Climate System, K.-M. Lau and D. E. Waliser, Eds., Springer, 1–16 . Mo, K

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Peter Caplan, John Derber, William Gemmill, Song-You Hong, Hua-Lu Pan, and David Parrish

1. Introduction The following changes were recently implemented in the National Centers for Environmental Prediction (NCEP formerly known as the National Meteorological Center’s) global analysis–forecast system: 1) direct use of cloud-cleared radiances in the analysis system, 2) modification of divergence increment at large scales, 3) inclusion of ERS-1 surface winds (20 November 1995), 4) modification of the parameterization of deep convection, and 5) improvement of the planetary boundary

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T. N. Krishnamurti, Mukul Tewari, D. R. Chakraborty, Jose Marengo, Pedro L. Silva Dias, and P. Satyamurty

1. Introduction Factors controlling freeze events over subtropical and tropical latitudes during the winter season generally are accompanied by a large-amplitude trough of the middle-latitude westerlies. The tropical extension (or penetration) of such a large-amplitude trough appears, clearly, to be associated with synoptic- to planetary-scale events. The frost over southeastern Brazil is known to have devastating effects on the coffee crops and a prediction of such events is of considerable

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Clark Evans, Steven J. Weiss, Israel L. Jirak, Andrew R. Dean, and David S. Nevius

- β -scale variability in the preinitiation and near-storm environments. One example of such variability is manifest through horizontal convective rolls in the daytime planetary boundary layer (e.g., Malkus and Riehl 1964 ; LeMone 1973 ). Observations in preconvective environments indicate that substantial variability in lower-tropospheric vertical thermodynamic profile structure and derived thermodynamic stability parameters exists across the several-kilometer wavelength of a single horizontal

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Masao Kanamitsu

-scale heatingtakes place in a stably stratified environment whenforcing creates supersaturation. The evaporation ofcondensed raindrops in unsaturated layers below cloudbase is also taken into consideration. The boundary layer physics in the model, developedmainly by the Geophysical Fluid Dynamics Laboratory(GFDL) of Princeton University and partly by NMC,is separated into the surface layer, where exchange between the earth's surface and atmosphere takes place,and the planetary boundary layer, where small

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Wayne F. Feltz and John R. Mecikalski

. The primary focus of this paper is not on the strong upper-level short wave, but rather is on the rapid thermodynamic destabilization that occurred within the Oklahoma–Kansas area on 3 May 1999, which assisted in initiating severe convection. Previous studies of the preconvective environment highlight the importance of changing planetary boundary layer (PBL) heat and moisture for the initiation of deep convection ( Beebe 1958 ; Carlson 1983 ; Sanders 1986 ; Colby 1984 ; Sanders and Blanchard

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Yi Jin, William T. Thompson, Shouping Wang, and Chi-Sann Liou

resolution. The simulated hurricane with the dissipative heating included had a 5–7 hPa larger central pressure deficit and 10% higher surface maximum winds when the winds exceed 65 m s −1 , a threshold value also suggested by BE98 . ZA99 , however, did not consider the dissipative heating effect due to the kinetic energy dissipation in the interior of the atmosphere, because it is usually one to two orders of magnitude smaller than that due to surface friction. The other numerical model that has

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Maziar Bani Shahabadi, Stéphane Bélair, Bernard Bilodeau, Marco L. Carrera, and Louis Garand

planetary boundary layer in the context of coupled land–atmosphere DA in NWP. Draper and Reichle (2019) used a weakly coupled land and atmosphere data assimilation system for NASA’s Global Earth Observing System model to demonstrate the advantage of assimilating satellite soil moisture into an atmospheric reanalysis. They reported a reduction of RMSE against independent station observations for various variables, including daily maximum 2-m temperature and 2-m specific humidity, when Advanced

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Christopher D. Hill

-wavelength ridges atthe planetary scale. This greatly affects the character of synoptic-scale disturbances that move through the region,and results in an increased importance of mesoscale processes and their interaction with the complex terrainof the area. This article discusses some of the important large-scale, synoptic-scale, and mesoscale factors asbackground for the following series of papers on specific western United States terrain-influenced forecast problems.1. Introduction The Western Region of the

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Piero Malguzzi, Andrea Buzzi, and Oxana Drofa

the physical parameterizations. In addition, a divergence damping term, defined by the following u and υ tendencies is applied at each gravity time step to diffuse the divergent part of the flow, preventing the accumulation of energy at small scales, especially in subtropical regions. c. Physical parameterizations The GLOBO physical scheme consists of the parameterizations of the surface layer (SL), of the planetary boundary layer (PBL), of the vertical diffusion in the “free” atmosphere, of

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