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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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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

, focusing on conditions dominated by thermal circulations and strong synoptic forcing. Another smaller study focused on fog formation, which will be a topic of future publications. The field site, equipment, and execution of the first two experiments are discussed next. Field site. The Granite Mountain Atmospheric Science Testbed (GMAST) is a part of the U.S. Army DPG shown in Fig. 1 . DPG is located 137 km southwest of Salt Lake City, Utah, and consists of 3700 km 2 of land in complex terrain with

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

Arritt 1992 ). During quiescent large-scale conditions, observational and numerical modeling studies have found that the daytime off-playa breeze (sometimes called a salt breeze) extends to as high as ~1000 m AGL and has 10-m wind speeds of 3–4 m s −1 (e.g., Davis et al. 1999 ; Rife et al. 2002 ; Knievel et al. 2007 ). These numerical studies required artificial forcing to produce a realistic off-playa breeze, however. To be specific, Davis et al. (1999) used a soil-dependent thermal inertia

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Joshua P. Hacker and Lili Lei

between the initial conditions and a forecast metric is spuriously large because of sampling error, and the analysis error statistics do not overestimate the covariance as severely, the sensitivity can be overestimated. Most results in the literature so far have used an approximation to the analysis error covariance, where it is assumed diagonal (e.g., Ancell and Hakim 2007 ; Torn and Hakim 2008 ). Across a broad range of problems, and in particular for mesoscale sensitivities lacking strong forcing

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

into several LSMs, including early versions of the National Centers for Environmental Prediction–Oregon State University–U.S. Air Force–Office of Hydrologic Development LSM known as Noah (e.g., Noilhan and Planton 1989 ; Ek and Mahrt 1991 ; Viterbo and Beljaars 1995 ; Chen and Dudhia 2001 ; Ek et al. 2003 ). MP81 produces higher-than-observed soil thermal conductivity in very wet conditions and lower-than-observed soil thermal conductivity in dry conditions for some soil textures ( Peters

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

schemes. The SCM is run over a 3 × 3 gridpoint stencil with periodic lateral boundary conditons, no external forcing, and the same physics packages and vertical grid spacing as in 4DWX-DPG, except in sensitivity studies involving radiation or PBL schemes. Simulations with varying C zil , radiation schemes, or PBL schemes use a soil moisture of 0.235 m 3 m −3 , whereas simulations with varying soil moisture, radiation schemes, or PBL schemes use a C zil of 0.518 over shrubland and 0.877 over playa

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Feimin Zhang and Zhaoxia Pu

-00131.1 . 10.1175/BAMS-D-13-00131.1 Findlater , J. , 1985 : Field investigations of radiation fog formation at outstations . Meteor. Mag. , 114 , 187 – 201 . Flanner , M. G. , and C. S. Zender , 2005 : Snowpack radiative heating: Influence on Tibetan Plateau climate . Geophys. Res. Lett. , 32 , L06501 , . 10.1029/2004GL022076 Flanner , M. G. , C. S. Zender , J. T. Randerson , and P. J. Rasch , 2007 : Present day climate forcing and response

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