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Joseph P. Zagrodnik, Lynn McMurdie, and Robert Conrick

foothills removed and control runs as a zoomed-in SW–NE cross section ( Fig. 13 ) and as a map ( Fig. 14 ). The vertical velocity difference in Fig. 13a shows that upward motion is reduced in the leftmost 20 km of the cross section by removing the foothills. The foothills removed run also diminished a wave train that was associated with the transition from ocean to the coastal foothills (faintly visible in Fig. 10a ). Of greater interest, a broad region of increased vertical velocity up to 8-km

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Hannah C. Barnes, Joseph P. Zagrodnik, Lynn A. McMurdie, Angela K. Rowe, and Robert A. Houze Jr.

the rawinsonde and KH waves, these data are expected to be generally representative of the conditions associated with the KH waves and the impact of this separation is discussed in section 3 . During OLYMPEX, rawinsondes were launched from the NPOL site and dropsondes were released over the ocean from the DC-8 aircraft during precipitating events of interest ( Petersen and Krajewski 2018 ). Geostationary infrared brightness temperatures from GOES-West and data from the National Centers for

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Robert Conrick, Clifford F. Mass, and Qi Zhong

et al. (2011) , using the Weather Research and Forecasting (WRF) Model, demonstrated that terrain-induced KH waves in the upper troposphere were not resolved at 3-km horizontal grid spacing but were at 1 km. Efimov (2017) used the WRF Model to simulate KH waves over Crimea, and Trier et al. (2012) simulated turbulence arising from KH instability in a winter cyclone. Thompson (2007) simulated the formation of KH instability in a sea-breeze front using the U.S. Navy’s Coupled Ocean

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Joseph P. Zagrodnik, Lynn A. McMurdie, Robert A. Houze Jr., and Simone Tanelli

that weaker rain shadows on the eastern slopes were favored in the prefrontal (warm frontal) periods of midlatitude cyclone passages, prior to the erosion of the preexisting stable air mass in the lee. Siler and Durran (2016) found that weaker rain shadows were associated with muted lee-wave activity, a consequence of low-level cold, stagnant air disfavoring descent in the lee. Mass et al. (2015) suggested a different mechanism for weak-rain-shadow scenarios: southeasterly upslope flow on the

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David J. Purnell and Daniel J. Kirshbaum

domain size is large enough to prevent gravity waves from fully recirculating through it over a 12-h integration period. Thus, the upstream flow is uncontaminated by such perturbations. The top boundary is rigid with a 8-km-deep sponge layer. The surface is mostly ocean, with just a strip of the Pacific Northwest in the center ( Fig. 8 ). This configuration eliminates discontinuities at the periodic boundaries while retaining important sea–land contrasts upstream of the Olympics. To focus on the

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Joseph P. Zagrodnik, Lynn A. McMurdie, and Robert A. Houze Jr.

1. Introduction The west coast of North America is frequented by landfalling extratropical cyclones from the Pacific Ocean during the fall through early spring. When these storms pass over coastal mountain ranges, they produce copious precipitation on the windward slopes, frequently contributing to hazards such as flooding and landslides. These storms are also responsible for the accumulation of snow at higher elevations, which is crucial for summer water supply. Understanding the processes

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Robert A. Houze Jr., Lynn A. McMurdie, Walter A. Petersen, Mathew R. Schwaller, William Baccus, Jessica D. Lundquist, Clifford F. Mass, Bart Nijssen, Steven A. Rutledge, David R. Hudak, Simone Tanelli, Gerald G. Mace, Michael R. Poellot, Dennis P. Lettenmaier, Joseph P. Zagrodnik, Angela K. Rowe, Jennifer C. DeHart, Luke E. Madaus, Hannah C. Barnes, and V. Chandrasekar

mountain range with permanent snow cover. Figure 1 shows the terrain of the Olympic Mountain range, which occupies the Olympic Peninsula of the state of Washington. The peninsula has a north–south coastline on the Pacific Ocean and is separated from Canada’s Vancouver Island on its north side by the narrow Strait of Juan de Fuca. Fig . 1. Map of the region where the OLYMPEX campaign occurred, including the mountainous terrain of the Olympic Peninsula. The motivation for OLYMPEX was not only to better

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Annareli Morales, Hugh Morrison, and Derek J. Posselt

condition. A positive definite advection scheme is used, and a Rayleigh damper with damping coefficient of 0.0003 s −2 is applied to the top 4 km to prevent reflection of vertically propagating gravity waves. Although interactions of radiation with the mountain surface can result in the forcing of mesoscale mountain circulations, for example, mountain-valley winds, our focus is on the interaction of microphysics and dynamics. Thus, radiative transfer and surface heat flux parameterizations are

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Yagmur Derin, Emmanouil Anagnostou, Marios Anagnostou, and John Kalogiros

methods to validate satellite constellation measurements with surface rainfall measured by dense rain gauge and disdrometer networks at various sites. One such campaign was OLYMPEX, which was conducted in the Pacific Northwest. The goal of OLYMPEX was to validate rain and snow measurements in midlatitude frontal systems as they moved from ocean to coast to mountains and determine how remotely sensed measurements of precipitation by GPM could be applied to a range of hydrological, weather forecasting

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Ousmane O. Sy, Simone Tanelli, Stephen L. Durden, Andrew Heymsfield, Aaron Bansemer, Kwo-Sen Kuo, Noppasin Niamsuwan, Robert M. Beauchamp, V. Chandrasekar, Manuel Vega, and Michael P. Johnson

. Oceanic Technol. , 22 , 1494 – 1506 , https://doi.org/10.1175/JTECH1808.1 . 10.1175/JTECH1808.1 Liebe , H. J. , 1985 : An updated model for millimeter wave propagation in moist air . Radio Sci. , 20 , 1069 – 1089 , https://doi.org/10.1029/RS020i005p01069 . 10.1029/RS020i005p01069 McFarquhar , G. M. , and Coauthors , 2017 : Processing of ice cloud in situ data collected by bulk water, scattering, and imaging probes: fundamentals, uncertainties, and efforts toward consistency. Ice

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