a. Threshold minimum velocity of 1.0 m s1.
Figure 7. Seasonal wind rose diagrams for the five sites and for Prudhoe Bay using three
threshold minimum velocities. The percentages listed for each season indicate the fractional
number of all data points for that season which met or exceeded the threshold criterion.
Labels for each octant indicate the mean wind speed for that direction for points that satisfied
the threshold criterion. Missing data values were excluded from all calculations.
By contrast, foothills IMN sees almost no winds with a significant easterly
component, while the intermediate SAG and WKU show a preponderance of SW
winds. Probabilities for strong winds (defined here as winds ≥10 m s1) are less
than 3% for any site in this season and less than 1% for the sites above the
coastal plain, while the rare strong winds tend to be from S to W. Though not
clearly evident from the plots shown here, during WS the upland sites, unlike
BET and FRA, did not show wind regimes that persisted several days. Also, the
strong wind events were frequently (though not always) quite transient and often
occurred near the end of the diurnal heating cycle consistent with outflow from
so-called air-mass convection. No winds exceeding 20 m s1 were seen at any site