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Qingfang Jiang and James D. Doyle

1. Introduction Moist processes have been largely ignored in the majority of mountain-wave studies, partially because of the complexity associated with moisture and microphysical processes. Studies of the interaction between moist airflow and mesoscale topography can be broadly classified into two categories. The first category includes quasi-analytical studies with highly simplified representations of moist processes. For example, a set of two-dimensional steady-state linear wave solutions

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Vanda Grubišić and Brian J. Billings

topography upwind, leeside disturbances are almost exclusively generated by the main massif of the Sierra Nevada range. Additionally, the proximity of the Pacific Ocean provides a source of upper-level moisture that commonly gives rise to clouds atop the mountain-wave crests. Conducting a climatology of mountain-wave events in the Sierra Nevada is difficult because of the lack of routine measurements that can be directly and unambiguously related to mountain-wave activity. While mountain waves do have a

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Juerg Schmidli, Gregory S. Poulos, Megan H. Daniels, and Fotini K. Chow

stability, cloudiness, and atmospheric moisture on the structure and strength of nocturnal drainage flows. The nonlinear interaction between nocturnal drainage flows and mountain waves has been investigated by Poulos et al. (2000 , 2007 ). The ability of high-resolution numerical models to simulate these thermally induced flows over complex terrain has been demonstrated by several studies in recent years. Zängl et al. (2001) , for example, investigated the very strong daytime valley winds in the Kali

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Juerg Schmidli, Brian Billings, Fotini K. Chow, Stephan F. J. de Wekker, James Doyle, Vanda Grubišić, Teddy Holt, Qiangfang Jiang, Katherine A. Lundquist, Peter Sheridan, Simon Vosper, C. David Whiteman, Andrzej A. Wyszogrodzki, and Günther Zängl

most models by the specified land surface characteristics. For the models where this is not the case, the albedo is set to 0.27. The soil temperature was initialized with the temperature of the lowest atmospheric level and the soil moisture saturation ratio was set to 20%, with the exception of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) for which the moisture availability was set to 20% (the MM5 soil model used does

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Patrick A. Reinecke and Dale R. Durran

is less than 80% in the 1–3-km layer with a minimum near 65% at 1.75 km. The importance of these differences in moisture will be discussed later. 2) IOP 13 For the IOP 13 case, the upstream profiles of U , θ , N , and RH are shown in Fig. 12 . The distinct layering of static stability in the troposphere is evident; however, the structure is considerably different between the strong and weak subsets. On one hand, for the strong subset, a classic layered structure of the static stability is

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Vanda Grubišić and Brian J. Billings

between 0900 and 1200 UTC 26 March. At 700 hPa, which is approximately at the height of the Sierra Nevada crest (∼3000 m), the upper-level low is producing strong west-southwest (WSW) flow and moisture advection across the Sierra Nevada at this time. The two operational radiosonde locations closest to the Sierra mountains are located in Reno and Desert Rock, Nevada. At 0000 UTC 26 March, the 700- and 500-hPa wind speeds at Reno were both 27.5 m s −1 , indicating there was little wind shear over the

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Gregory S. Poulos, Junhong Wang, Dean K. Lauritsen, and Harold L. Cole

the critical line-of-sight intersection height H C we find where R is the dry gas constant for air. This equation does not consider the effects of atmospheric moisture on W s and in practice could be calculated using the U.S. Standard Atmosphere, 1976 or radiosonde data. The value of U ag depends on H a , the aeronautical characteristics of the particular airborne sonde platform, and environmental conditions. For example, at maximum cruising altitude, 15.27 km (51 000 ft), a

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Yanping Li, Ronald B. Smith, and Vanda Grubišić

wintertime, snow cover increases surface albedo, sharply decreasing the ground sensible heating. In summertime, reduced soil moisture increases the Bowen ratio and the proportion of net radiation converted to sensible heating. To study the seasonal character of the diurnal valley circulation, a series of WRF idealized simulations have been done with a fixed valley depth ( h m = 2000 m) but with modified sensible heating. As heating is increased from 0 to 300 W m −2 , two distinct regimes are seen, with

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Bowen Zhou and Fotini Katopodes Chow

Coriolis parameter, is a scalar (e.g., temperature, moisture), and S is a generic source–sink term. The filter can be considered a density-weighted Favre filter , where φ is generic variable ( Favre 1983 ). The turbulent stresses τ ij and scalar fluxes χ i are represented by the 1.5-order turbulent kinetic energy–based closure (TKE-1.5) of Moeng (1984) . More details on the turbulence model are given in Xue et al. (2000) . 4. Results and discussion a. Transient warming Figure 2 presents

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Peter Sheridan and Simon Vosper

affecting the flow in the valley) and more generally on the wavelength and amplitude of the waves. The results of three tests are shown in Figs. 11d–f : 1) replacing the winds in the control simulation below roughly 7 km with those from the 1458 LST MGAUS profile and using the MGAUS moisture profile ( Fig. 11d ), 2) additionally incorporating the temperature profile measured by the BAe-146 aircraft at 1730 LST ( Fig. 11e ), and 3) repeating test 1 but with the radiation parameterization disabled ( Fig

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