Numerical Studies Pertaining to Airflow on the West Coast of the US
Abstract
LONG TERM GOALS. The long term goal of this project is to improve our understanding and forecasting of coastally trapped disturbances (CTD) that occur along the west coast of the U.S. in spring and summer. The passage of a CTD is generally associated with a sudden change in the local weather from clear skies to dense stratus clouds. OBJECTIVES. During this last year we have focused our investigations on two outstanding questions regarding the processes that maintain the amplitude of CTDs as they propagate northward along the west coast. The first question is how CTDs maintain their strength while propagating around the coastal bends and across the gaps in the Pacific Coast Ranges. The second question is how CTDs persist without losing their energy though the generation of upward propagating gravity waves. APPROACH Our investigation has employed a hierarchy of numerical models and analytic theory. A three-dimensional nonhydrostatic model for the simulation of stratified air flow over topography has been used to study the propagation of CTDs along both a smoothed profile of the actual west coast topography and more idealized ridges. Shallow-water models have been used to investigate the horizontal structure of disturbances propagating along both straight and curved side-walls. Analytic theory has been used to describe the small-amplitude response of the fluid in idealized environments. These approaches are coordinated in an effort to arrive at the simplest physical description of the phenomena that is consistent with the available observations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1997
- Accession Number
- ADA633497
Entities
People
- Dale R. Durran
Organizations
- University of Washington