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FLOHOF

Flow over and around Hofsjökull

Satellite picture and topography of the Hofsjøkull area.
Satellite picture and topography of the Hofsjøkull area.

Hofsjökull (1782 m) is an isolated, glacier covered mountain in Central Iceland with nearly circular shape and extremely smooth surface. At an diameter of around 30 km it rises about 1000 m above its surrounding. There are presumably only few mountains on earth of this scale whose shape comes so close to that assumed in idealized theoretical work. This makes Hofsjökull an ideal field laboratory for validation purposes. It is a central aim of FLOHOF to explore the response of mountain induced gravity waves to changes of the inflow in time. As yet, this topic received little attention from the theoreticians. We are not aware of any campaign to address this topic observationally.

During summer 2007 the FLOHOF field campaign has been conducted in the Hofsjökull area. Permanent meteorological stations have been placed around and over the mountain. In addition atmospheric profiles of temperature, humidity and wind have been taken by small umnanned remotely piloted airplanes, tethered balloons, and pilot balloon ascents. The campaign has been accompanied by extensive numerical simulations using MM5 and WRF.

There are also attempts to make progress with linear theories on the description of non-stationary gravity waves. In particular, the observations collected during FLOHOF will be used as input to linear models. Evaluation of the observations is of primary importance at the moment. It is planned to perform first a principal oscillation analysis (POP) in order to find out about main frequencies and the related pressure patterns. Corresponding enquiries into the capability of POPs to handle spatially inhomogeneous data sets are under way.

FLOHOF is an international research project with participants from Iceland (Institute for Meteorological Research, Reykjavik; University of Iceland, Reykjavik; Icelandic Meteorological Office), Norway (University of Bergen), Germany (Ludwig-Maximilians University, Munich; University of Applied Sciences Regensburg), France (ENAC, Toulouse) and Switzerland (ETH Zürich).

More information on the FLOHOF project homepage:

Duration: 2007-

Contact at GFI:
Joachim Reuder

Haraldur Olafsson

Thomas Spengler

References:

Reuder, J., M. Ablinger, H. Agustsson, P. Brisset, S. Brynjolfsson, M. Garhammer, T. Johannesson, M. O. Jonassen, R. Kühnel, S. Lämmlein, T. de Lange, C. Lindenberg, S. Malardel, S. Mayer, M. Müller, H. Olafsson, O. Rögnvaldsson, W. Schäper, T. Spengler, G. Zängl, and J. Egger, 2012
FLOHOF 2007: An overview of the mesoscale meteorological field campaign at Hofsjökull, Central Iceland.
Meteorol. Atmos. Phys., 116, 1-13, DOI: 10.1007/s00703-010-0118-4. (access)

Mayer, S., A. Sandvik, M. Jonassen, and J. Reuder , 2012
Atmospheric profiling with the UAS SUMO: a new perspective for the evaluation of fine-scale atmospheric models.
Meteorology and Atmospheric Physics, 116, 15-26, DOI10.1007/s00703-010-0063-2. (access)

Egger, J., 2009
Time varying flow over mountains: temperature perturbations at the surface.
Meteorologische Zeitschrift, 18, 1, 101–106. (access)

Egger, J., and R. Kühnel, 2010
Orographic gravity waves induced by variable mean winds: observations at Hofsjökull. Meteorologische Zeitschrift, 19, 1, 101–113. (access)

Kühnel, R., 2008
Observations and results of the FLOHOF Field Campaign 2007.
Diploma thesis, Meteorological Institute, Ludwig-Maximilians-University, Munich, Germany. (pdf)