Flow in Complex Terrain: Observations by Radar Wind Profilers and Anemometers near Juneau, Alaska

Abstract

Four years of data from three radar wind profilers and collocated anemometers are used to examine the airflow regimes near Juneau, Alaska. Wind direction probability density functions and wind rose histograms show the dominant wind speeds and directions from a long time series of observations. Analysis of diurnal variation separates mountain?valley flow events from synoptically driven events. Flow constrained by the Gastineau Channel dominates the winds near downtown Juneau, and the wind profilers document the rotation of this flow as it merges with the synoptic flow above the surrounding mountains. Strong flows from the northeast over the Taku Glacier, locally known as ?Taku flows,? are also documented. These flows are less frequent but can cause strong wind storms at the surface. In addition, local flow effects are seen, including winds turning in response to terrain influence, drainage flows in creek valleys, and cross-valley flows. This analysis also demonstrates that radar wind profilers, using recently developed data-processing algorithms [in this case the National Center for Atmospheric Research (NCAR) Improved Moments Algorithm?NCAR Winds and Confidence Algorithm (NIMA?NWCA)], can provide valuable data even at low altitudes near complex terrain and sources of ground clutter.