Various measurement methods used to determine the local wind field on and around Mount Washington, New Hampshire

Different investigations made during the last years hint at the growing importance of extreme storms worldwide. They are related to threats for health and life of man and animals as well as to big economic damages. To make satisfying observations of such situations with extreme wind speeds in field experiments is extremely difficult: Small-scale travel ways of hurricanes are quite well predictable; exact forecasts of stronger wind cur-rents that show extreme wind speed peaks (which occur locally most of the time) are not possible. An ideal placement of measurement instrumentation is not given and thus, measuring and quantifying such events happens more or less by chance. In addition to this, there is virtually no one measurement apparatus which is suited to bear with the damaging forces of a hurricane on the one hand and to measure the fine structure of the wind field on the other hand. However, one has to take into account that damage to the measurement instrumentation is not only due to the high wind speed but furthermore to rubble which is transported within the hurricane.

Wind measurements on Mt. Washington (NH) provide a solution to this problem: The observatory on its summit records climatic conditions throughout the whole year. The extreme conditions observed here can be summarized as follows: - Days with wind speed > 100 mph ca. 60 to 75 a year. - Days with wind speed > 75 mph about 104 days a year. - Highest wind speed ever measured by men: 231 mph with an hourly average of 173 mph.

The research project covers the following investigations:

1. Characterizing of wind field on the meso-scale on the upper slopes of Mt. Washington using vegetation and snow dune formations

2. Horizontal and vertical structure of wind in the boundary layer of the summit plateau during different wind events with high spatial and temporal resolution measured by three- dimensional sonic anemometers

3. Investigation of wind field generated by flow towards and around buildings including turbulence by determin-ing the growth of Rime Ice and mapping of areas of snow accumulation and erosion

4. Spatial and temporal appearance of gusts as well as their periodicity during extremely high wind speed events measured by three- dimensional sonic anemometers

5. Enhancement and re-development of existing modeling procedures and numeric simulation methods for micro- scale wind fields and gusts in built up structures. These are based on the micro-scale, prognostic model ENVI- met which was developed at the Department of Geography, Ruhr-University of Bochum, Germany.

First results will be shown here.