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RISWintertime Cold-Air Pools in the Bavarian Danube Valley Basin: Data Analysis and Idealized Numerical Simulations
Publisher: American Meteorological Society
Abstract: This paper investigates wintertime cold-air pools in a basinlike part of the Danube Valley, located in the German state of Bavaria. Specifically, the focus is on cold-pool events restricted to the basin area, that is, not ...
An Improved Method for Computing Horizontal Diffusion in a Sigma-Coordinate Model and Its Application to Simulations over Mountainous Topography
Publisher: American Meteorological Society
Abstract: A set of modifications is presented to reduce the unphysical impact of horizontal diffusion in numerical models with a terrain-following sigma-coordinate system. At model levels sufficiently far away from the ground, ...
A Generalized Sigma-Coordinate System for the MM5
Publisher: American Meteorological Society
Abstract: A generalized sigma-coordinate system is presented that allows for a rapid vertical decay of small-scale topographic structures in the coordinate surfaces. Its properties are similar to the smooth-level vertical-coordinate ...
Dynamical Aspects of Wintertime Cold-Air Pools in an Alpine Valley System
Publisher: American Meteorological Society
Abstract: This study presents high-resolution numerical simulations in order to examine the dynamical mechanisms controlling the persistence of wintertime cold-air pools in an Alpine valley system. First, a case study of a cold-pool ...
An Adaptive Vertical Coordinate Formulation for a Nonhydrostatic Model with Flux-Form Equations
Publisher: American Meteorological Society
Abstract: The concept of adaptive vertical coordinates is used to upgrade conventional terrain-following σ coordinates to arbitrary hybrid coordinates. Compared with previous approaches for implementing adaptive coordinates, the ...
Interaction between Dynamics and Cloud Microphysics in Orographic Precipitation Enhancement: A High-Resolution Modeling Study of Two North Alpine Heavy-Precipitation Events
Publisher: American Meteorological Society
Abstract: Interactions of atmospheric dynamics and cloud microphysics with the Alpine orography are investigated for two north Alpine heavy-precipitation cases (20?22 May 1999 and 22?23 August 2005). Both cases were related to a ...
Extending the Numerical Stability Limit of Terrain-Following Coordinate Models over Steep Slopes
Publisher: American Meteorological Society
Abstract: o extend the numerical stability limit over steep slopes, a truly horizontal pressure-gradient discretization based on the ideas formulated by Mahrer in the 1980s has been developed. Conventionally, the pressure gradient ...
Formation of Extreme Cold-Air Pools in Elevated Sinkholes: An Idealized Numerical Process Study
Publisher: American Meteorological Society
Abstract: High-resolution numerical simulations with the fifth-generation Pennsylvania State University?National Center for Atmospheric Research (PSU?NCAR) Mesoscale Model (MM5) are presented to investigate the processes leading to ...
Orographic Gravity Waves Close to the Nonhydrostatic Limit of Vertical Propagation
Publisher: American Meteorological Society
Abstract: Orographic gravity waves excited by a narrow mountain ridge are investigated with the aid of numerical simulations. When the nondimensional mountain half-width Na/U is around 1?N, a, and U being the Brunt?Väisälä frequency, ...
Diurnal Circulation of the Bolivian Altiplano. Part II: Theoretical and Model Investigations
Publisher: American Meteorological Society
Abstract: The first step in the evolution of the diurnal circulation of grand plateaus is the matutinal buildup of inflow through mountain passes connecting the lowlands with the plateau proper. Maximum inward transport is attained ...