Simulations of the wind field for the summit area of Mount Washington taking into account different conditions of air flow during the measurement period of 60 years in the 20th century

Mt. Washington in New Hampshire is famous for its special wind conditions, especially the windrecord which has been held since 1932. But since the beginning of wind measurements the instrument locations at the summit of Mount Washington have changed from the “Stage Office” to the “Old Observatory” and now to the new one. Over the years, the number and structure of buildings at the summit has changed more than once and the ability to measure wind speed and direction accurately became more and more difficult as newer buildings obstructed free airflow. From 1980 onward, measurement conditions have become better than before, but differ completely from those during the period of 1932-1980. To provide answers about the comparability of the database and about the likelihood of breaking the wind record in future at the current location a research plan for measuring and modeling the wind conditions at Mount Washington’s summit has been developed.

Measurements have been made during the last 3 years at locations where the wind record was measured (Stage Office) and at the tower of the new Observatory. During this period, wind vectors and air temperature were measured using three- dimensional sonic anemometers with a mean sample time of one second. The first results clearly show that there are small differences in wind direction but big differences in vertical and horizontal wind speed between Tower and Stage Office.

As the old observatory has been torn down in the meanwhile, comparing measurements of this kind are not possible. In order to find differences between the wind field without buildings, the building structure in 1932, 1950 and the current situation, we modelled the summit wind field under these different conditions with 12 wind directions and different wind speeds.

An important conclusion from these measurements as well as from the simulations is, that direct and simple transfer of the data obtained at the three different measurement locations is not possible as the relationships between the two measurement sites are complex.