Atmospheric mass transport by along-valley wind systems in a deep Colorado valley.

Abstract

Hourly tethered balloon wind soundings from the 650 m deep, narrow, Brush Creek Valley of Colorado were analyzed to determine the nocturnal atmospheric mass (or volume) budget of the valley. Under the assumption that the volume flux on an entire valley cross section can be approximated from balloon soundings over the valley centre, volume fluxes were calculated from tethered balloon profiles taken at several points along the valley's longitudinal axis in a 7 km long segment of the valley. Down valley volume fluxes increased in the 3 h following sunset to levels that were basically maintained through the night. Down valley volume fluxes increased with distance down the valley axis from 0.9 million m SUP 3 s SUP - SUP 3 at the upper end of the segment to 2.8 million m SUP 3 s SUP - SUP 1 at the lower end, producing an average volume flux divergence of 271 m SUP 2 s SUP - SUP 1. Mean vertical velocity profiles through the valley's depth were calculated, and an error analysis was performed. (from paper)