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Implicit–explicit (IMEX) linear multistep methods are examined with respect to their suitability for the integration of fast-wave–slow-wave problems in which the fast wave has relatively low amplitude and need not be accurately simulated. The widely used combination of trapezoidal implicit and leapfrog explicit differ-encing is compared to schemes based on(More)
• p. 28, line 4: " Chap. 2 " should be " Chap. 3 " Chapter 2 • p. 38, text line 14: " t n " should be " τ n " • p. 39, second line in first equation after (2.12) is missing an " (" ; it should begin = (1 + λ∆t)[(1 • p. 39, last equality in (2.13) should be " ≤ " • p. 40, line 10: Replace " Define the amplification " with " For homogenous ODE, define the(More)
An efficient method for scalar advection is developed that selectively preserves monotonicity. Monotonicity preservation is applied only where the scalar field is likely to contain discontinuities as indicated by significant grid-cell-to-grid-cell variations in a smoothness measure conceptually similar to that used in weighted essentially non-oscillatory(More)
Two-dimensional simulations of the 11 January 1972 Boulder, Colorado, windstorm, obtained from 11 diverse nonhydrostatic models, are intercompared with special emphasis on the turbulent breakdown of topographically forced gravity waves, as part of the preparation for the Mesoscale Alpine Programme field phase. The sounding used to initialize the models is(More)
The development of shallow cellular convection in warm orographic clouds is investigated through idealized numerical simulations of moist flow over topography using a cloud-resolving numerical model. Buoyant instability , a necessary element for moist convection, is found to be diagnosed most accurately through analysis of the moist Brunt–Väisälä frequency(More)
Persistent, 10-km-scale gradients in climatological precipitation tied to topography are documented with a finescale rain and snow gauge network in the Matheny Ridge area of the Olympic Mountains of Wash-ington State. Precipitation totals are 50% higher on top of an ϳ800-m-high ridge relative to valleys on either side, 10 km distant. Operational(More)
The sensitivity of downslope wind forecasts to small changes in initial conditions is explored by using 70-member ensemble simulations of two prototypical windstorms observed during the Terrain-Induced Rotor Experiment (T-REX). The 10 weakest and 10 strongest ensemble members are composited and compared for each event. In the first case, the 6-h(More)
The formation of lee wakes and vortices is explored in the context of stratified flow with uniform basic-state wind and stability past elongated free-slip ridges. The theory of inviscid flow past a ridge of small nondimensional height ⑀ is revisited using a weakly nonlinear semianalytic model to compute flow fields through O(⑀ 2). Consistent with previous(More)
An incompressibility approximation is formulated for isentropic motions in a compres-sible stratified fluid by defining a pseudo-density ρ * and enforcing mass conservation with respect to ρ * instead of the true density. Using this approach, sound waves will be eliminated from the governing equations provided ρ * is an explicit function of the space and(More)