Wind climatology of the Mount Washington Observatory (1935-2013)

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atmospheric sciences and chemistry , applied meteorology , 2015
Cronin, Kevin Patrick
The Mount Washington Observatory (MWO), which is located on the summit of Mount Washington, New Hampshire (44.27° N,71.30° W, 1917m ASL), has operated and maintained more than 80 years of continuous weather observations. This is the first climatological analysis of the digitized MWO wind record (1935-present) and incorporates data from 1935-2013. The MWO station site changes and obstructions on the summit made a measurable impact on the wind record. This study did not account for the site changes or obstructions on the summit and did not attempt to make corrections on the record. Since the anemometer moved in 1980 to the current location on the Sherman Adams Building, it has been fully exposed to the prevailing westerly wind direction. Wind speed and directional diel patterns exist during all seasons with the most consistent diel pattern seen in the summer. Summer wind speed peaks before sunrise and decrease to a minimum in the early afternoon indicating frequent planetary boundary layer exposure. The weak winter diel wind cycle implies regular exposure to the free troposphere in the winter where synoptic scale patterns dominate wind variability. The influence of large-scale atmospheric circulation patterns (e.g., Arctic Oscillation) on Mount Washington wind speed is strongest during the cold season, but is relatively weak. A Theil-Sen's slope trend analysis of the Mount Washington wind record from 1981-2013 reveals a decrease of 0.25 m s-1decade-1. Although the finding is not statistically significant, it is consistent with similar decreasing trends observed at other Northern Hemisphere mid-latitude stations that may be a result of Arctic amplification.