Long-term declining trends in historical wind measurements at the Blue Hill Meteorological Observatory, 1885-2021

Trabajo presentado en AGU FALL MEETING, celebrado en Chicago (Estados Unidos) del 12 al 16 de diciembre de 2022.
The Blue Hill Meteorological Observatory, located on the 635-foot summit of Great Blue Hill ten miles south of Boston, Massachusetts, has been the site of continuous monitoring of the local weather and climate since its founding in 1885. The meticulous, extensive, and high-quality climate record maintained at this location has included the measurement of wind among many other parameters since its earliest days, and this provides a unique opportunity to examine seasonal and annual wind speed trends at this site over more than 135 years. Although multiple wind sensors have been in use during this time and the height of the anemometers was raised in 1908, the wind records have been made as consistent as possible through careful analysis of these changes and the application of adjustments to ensure consistency. An analysis of wind data homogeneity is being performed to associate statistical change points in monthly mean wind speeds to the documented wind instrument metadata. The running 30-year mean wind speed at Blue Hill Observatory has decreased from 7.0 m s-1 in the middle 20th century to its present value of 5.7 m s-1 with an increase in the rate of the decline beginning around 1980, and these changes persist in all seasons. The annual wind speed time series shows a significant (p < 0.05) downward trend over the entire period of record from 1885-2021 (-0.103 m s-1 decade-1) that is steeper and is also significant for the sub-periods from 1961-2021 (-0.274 m s-1 decade-1) and 1979-2012 (-0.339 m s-1 decade-1; the lowest annual mean wind speed was recorded in 2021). In addition, daily wind data for the last 60-70 years have been digitized including wind speed, peak gust, fastest mile, and prevailing direction, and this detailed data provides further characterization of the wind changes in recent decades at this location. The declining wind speed trend at Blue Hill has significant implications for the efficiency of wind power generation in the area if it reflects a regional shift in the near-surface wind regime and for the analysis of causal changes in large-scale climate dynamics.