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Thomas R. Parish and Larry D. Oolman

Forecasting Nonhydrostatic Mesoscale Model (NAM) for July 2008 are used here to depict the basic structure of the LLJ. Three-hourly output grids are used for each day based on the 0000 UTC forecasts, commencing at 0300 UTC and continuing until 0000 UTC the following day. Inspection of the mean values for July 2008 shows that the NAM is able to simulate the LLJ. As an example, Fig. 1a shows the mean July 2008 LLJ vertical profile at selected times of the day for the grid point corresponding to Enid

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Yuan Wang, Lifeng Zhang, Jun Peng, and Jiping Guan

imply that gravity waves in the mei-yu front system are substantially different from traditional (classical) frontal gravity waves? How will the prominent role of the moisture and diabatic heating in the mei-yu front system affect gravity waves? Both topics are worth exploring and studying. Recently, Peng et al. (2014a , b) constructed an idealized mei-yu front model based on the Weather Research and Forecasting (WRF) Model and used it to study the mesoscale energy spectral characteristics of the

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Michael M. Bell and Michael T. Montgomery

conjunction with NASA Genesis and Rapid Intensification Processes (GRIP) and National Oceanic and Atmospheric Administration (NOAA) Intensity Forecast Experiment (IFEX) campaigns. Composite analyses of developing and nondeveloping disturbances (“developers” and “nondevelopers”) using the PREDICT dataset have revealed distinctions between favorable and unfavorable thermodynamic environments for genesis. Montgomery and Smith (2012) , Davis and Ahijevych (2013) , and Komaromi (2013) showed that

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F. J. Robinson, S. C. Sherwood, D. Gerstle, C. Liu, and D. J. Kirshbaum

associated with unobservable details or stochastic behavior and reveal model errors that would not be detectable in a single event. Second, contrasting results in different forcing situations can reveal aspects that are more important to the interaction of convection with larger scales. Several previous studies have followed this strategy. J. Wu et al. (2009) found that the Weather Research and Forecasting (WRF) CRM was able to simulate qualitatively the significant differences in the character of

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Jih-Wang Aaron Wang and Prashant D. Sardeshmukh

Abstract

Global upper tropospheric kinetic energy (KE) spectra in several global atmospheric circulation datasets are examined. The datasets considered include the ERA-Interim, JRA-55, and ERA5 reanalyses and two versions of NOAA-GFS analyses at horizontal resolutions ranging from 0.7° to 0.12°. The mesoscale portions of the spectra are found to be highly inconsistent. This is shown to be mainly due to inconsistencies in the scale-dependent numerical damping and in the large contributions to the global mesoscale KE from the KE in convective regions and near orography.

The spectra also generally have a steeper mesoscale slope than the -5/3 slope of the observational Nastrom-Gage spectrum pursued at many modeling centers. The sensitivity of the slope in global models to 1) stochastically perturbing diabatic tendencies and 2) decreasing the horizontal hyper-viscosity coefficient is explored in large ensembles of 10-day forecasts made with the NCEP-GFS (0.7° grid) model. Both changes lead to larger mesoscale KE and a flatter spectral slope. The effect is stronger in the modified hyper-viscosity experiment.

These results show that (a) despite assimilating vastly more observations than used in the original Nastrom-Gage studies, current high-resolution global analyses still do not converge to a single “true” global mesoscale KE spectrum, and (b) model KE spectra can be made flatter not just by increasing model resolution but also by perturbing model physics and decreasing horizontal diffusion. Such sensitivities and lack of consensus on the spectral slope also raise the possibility that the true global mesoscale spectral slope may not be a precisely -5/3 slope.

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Mankin Mak, Yi Lu, and Yi Deng

recent years, there have been a number of investigations of fronts using 3D primitive equation models ( Rotunno et al. 1994 ; Zhang 2004 ) and nonhydrostatic models ( Plougonven and Snyder 2007 ; Wei and Zhang 2014 ) of increasingly fine resolution. The more recent investigations primarily focus on the generation of mesoscale gravity wave modes in a jet–front system. The sensitivity studies suggest that it would require grid resolution of 25 km or less to adequately resolve the properties of such

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Peter V. Hobbs, Clifford F. Mass, and Mark T. Stoelinga

storms on the Washington coast (the CYCLES Project), which led to a classification of rainbands in extratropical cyclones and detailed information on cloud structures and precipitation processes in the various types of rainbands. Within the past decade, Mass and colleagues have used observations and model simulations from the COAST Project, as well as daily real-time mesoscale model forecasts, to study fronts and precipitation in the Pacific Northwest, including the effects of orography. Problems

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M. E. B. Gray

tropical cloud clusters. Part III: Effects of mesoscale convective organization. J. Atmos. Sci., 46, 1566–1588. Cotton, W. R., H. Jiang, S. C. R. Rafkin, G. D. Alexander, and R. L. McAnelly, 1996: Parametrization of cumulus and MCSs in GCMs to mesoscale models. Proc. ECMWF Workshop on New Insights and Approaches to Convective Parametrization, Reading, United Kingdom, European Centre for Medium-Range Weather Forecasts, 288–305. Donner, L. J., 1993: A cumulus parameterization including mass

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Mitchell W. Moncrieff and Changhai Liu

consistent with fast eastward propagation (about 17 m s −1 ). A similar three-branch morphology occurs in simulations by Trier et al. (2006) for the same period using the Weather Research and Forecasting (WRF) model and in many simulations cited in the introduction to this paper. The simulated propagation speed compares to the Carbone et al. (2002) radar estimates. It has long been known that fast-moving systems with deep mesoscale downdrafts occur widely over the United States ( Houze et al. 1989

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Malakondayya Challa, Richard L. Pfeffer, Qiang Zhao, and Simon W. Chang

work done by the symmetric flow across the isobars. In our later investigations we used the 3D Naval Research Laboratory (NRL) mesoscale model developed by Madala and Chang (1979) and Madala et al. (1987) , which is a version of the Navy Operational Regional Atmospheric Prediction System (NORAPS). As in the earlier simulations with Sundquist’s model, hurricanes developed from the initial conditions corresponding to the developing disturbances and did not develop from those corresponding to the

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