The Atmospheric Boundary Layer at the Aletsch Glacier (3600 m - Switzerland)

Observations of the atmospheric boundary layer (ABL) were obtained during the unusually warm period of April through to August 2003 at the Jungfraujoch Observatory -3580 m. Sonic anemometers were deployed at the Aletsch Glacier to evaluate the turbulent fluxes of momentum and heat. Aerosol optical properties and water vapor profiles were also measured with EPFL Lidar systems. Three typical cases of PBL height were identified over the Swiss plateau: low (under 3600m), medium (reaching 3600m) and high PBL (above 3600m). We present observations of the exceptionally high altitude daytime ABL (~5000 m) and the persistence of the nocturnal residual layer. These results are supported also by local (meteorology at Jungfraujoch) and regional (close European meteorological soundings) as complementary measurements.