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Raquel Lorente-Plazas and Joshua P. Hacker

augmentation in ensemble filter data assimilation, is explored for simultaneously estimating and correcting observation biases and a bias in model forcing. The emphasis is on understanding the effectiveness of observation bias estimation in the presence of varying levels of model error. It is impossible to a priori determine whether biases in the state estimates result from biased observations or model deficiencies, because both can cause systematic departures of the predicted state from observations. An

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Hailing Zhang, Zhaoxia Pu, and Xuebo Zhang

performances of different PBL schemes in simulating near-surface temperature and wind speed and direction. Their results revealed that the model could reproduce diurnal variations in surface temperature and wind direction. However, all the boundary layer schemes underestimated (overestimated) wind speeds during the daytime (nighttime). Their study was conducted over the central United States during the summer, where little organized convection and topographical forcing was present. The problem becomes more

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Robert S. Arthur, Katherine A. Lundquist, Jeffrey D. Mirocha, and Fotini K. Chow

WRF, version 3.6.1) is modified to include topographic effects on radiation, expanding on the implementation of Lundquist et al. (2010) . Changes to the model are validated by confirming agreement in radiation and land surface fluxes, as well as temperature and velocity fields, between WRF-IBM and standard WRF when the same initialization and forcing conditions are applied. The validation is performed in a domain with an idealized two-dimensional valley that is forced by incoming solar radiation

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Jeffrey D. Massey, W. James Steenburgh, Sebastian W. Hoch, and Derek D. Jensen

heat flux G : where downwelling R n and G and upwelling H and LE are defined as positive. Near-surface forecasts are affected not only by the local partitioning among these components but also by regional differences, which can drive mesoscale circulations (e.g., Segal and Arritt 1992 ) and influence cloud development, precipitation, and atmospheric stability ( Stull 1988 ). The partitioning of R n into G , H , and LE is strongly influenced by the near-surface (0–10 cm) soil moisture

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Feimin Zhang and Zhaoxia Pu

different experiments. However, all experiments tend to underestimate the downward longwave radiation ( Fig. 5a ) and overestimate the downward shortwave radiation ( Fig. 5c ) during the daytime, respectively, perhaps because of the lack of overlying cloud during the daytime in the model simulations, this might relate to the lack of cloud parameterization or uncertainties in ice microphysics. Meanwhile, the downward longwave radiation ( Fig. 5a ) is also underestimated by the different experiments

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Sean M. Wile, Joshua P. Hacker, and Kenneth H. Chilcoat

1. Introduction Fog events in the Salt Lake basin in Utah, with impacts on aviation operations at the Salt Lake City International Airport (KSLC), arise in a range of flow scenarios. Typically, weak synoptic forcing and nonlinear water phase changes present challenges to numerical weather prediction (NWP) models when fog is possible. Because interactions between the land–water surface and the lower atmosphere can strongly modulate fog production and dissipation, near-surface shelter and

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H. J. S. Fernando, E. R. Pardyjak, S. Di Sabatino, F. K. Chow, S. F. J. De Wekker, S. W. Hoch, J. Hacker, J. C. Pace, T. Pratt, Z. Pu, W. J. Steenburgh, C. D. Whiteman, Y. Wang, D. Zajic, B. Balsley, R. Dimitrova, G. D. Emmitt, C. W. Higgins, J. C. R. Hunt, J. C. Knievel, D. Lawrence, Y. Liu, D. F. Nadeau, E. Kit, B. W. Blomquist, P. Conry, R. S. Coppersmith, E. Creegan, M. Felton, A. Grachev, N. Gunawardena, C. Hang, C. M. Hocut, G. Huynh, M. E. Jeglum, D. Jensen, V. Kulandaivelu, M. Lehner, L. S. Leo, D. Liberzon, J. D. Massey, K. McEnerney, S. Pal, T. Price, M. Sghiatti, Z. Silver, M. Thompson, H. Zhang, and T. Zsedrovits

north to northeast in DPG). Shown in the inset are the control center (red arrow) and Ditto meteorological building (circled) of GMAST. As the nocturnal stable boundary layer (SBL) breaks down during the morning transition, paving the way for a daytime convective boundary layer (CBL), a flow reversal occurs from downslope/downvalley to upslope/upvalley. Upslope flow may separate on the slopes in the form of thermal plumes, topped by cumulus clouds ( Banta 1984 ; Hocut et al. 2015 ). During the

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Jeffrey D. Massey, W. James Steenburgh, Sebastian W. Hoch, and Jason C. Knievel

(amount and type), fog and clouds, air quality, and surface and boundary layer winds (e.g., Hanna and Yang 2001 ; Rife et al. 2002 ; Marshall et al. 2003 ; Holt et al. 2006 ). There have been numerous hypotheses concerning the sources of these NST forecast errors ranging from inadequate horizontal or vertical resolution to the inaccurate initialization and parameterization of boundary layer and land surface characteristics and processes (e.g., Hanna and Yang 2001 ; Mass et al. 2002 ; Marshall

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Jeffrey D. Massey, W. James Steenburgh, Jason C. Knievel, and William Y. Y. Cheng

; Wyszogrodzki et al. 2013 ), 2) radiation parameterization errors due to the absence of three-dimensional scattering in complex terrain or tuning for lower elevations ( Zhong and Fast 2003 ; Liu et al. 2008b ; Wyszogrodzki et al. 2013 ), 3) underprediction of thermally forced circulations due to smoother-than-real topography making the associated subsidence warming over valleys and basins less intense during the day ( Liu et al. 2008b ), 4) decreased solar radiation due to excessive mountain cloud

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