OBSERVATIONS AND SIMULATIONS OF KATABATIC FLOWS DURING A HEATWAVE IN ICELAND

Abstract: Katabatic flows during the night of 11–12 August 2004 in Iceland are studied using observations and a numerical weather prediction model. During this period, there was a heatwave in Iceland. In relation with the very high daytime temperatures, weak synoptic winds and clear skies, a radiati...

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Bibliographic Details
Main Authors: Ágústsson, Hálfdán; Háskóli Íslands, Bústaðavegi 9, 150 Reykjavík, Iceland; halfdana@hi.is, Cuxart, Joan; Universitat de les Illes Balears, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain, Mira, Toni; Universitat de les Illes Balears, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain, Ólafsson, Haraldur; Háskóli Íslands, Bústaðavegi 9, 150 Reykjavík, Iceland
Format: Text
Language:English
Published: Croatian meteorological society; info@meteohmd.hr 2005
Subjects:
Katabatic winds;stable boundary layer;Iceland
Iceland
Online Access:http://hrcak.srce.hr/64691
http://hrcak.srce.hr/file/96963
Description
Summary:Abstract: Katabatic flows during the night of 11–12 August 2004 in Iceland are studied using observations and a numerical weather prediction model. During this period, there was a heatwave in Iceland. In relation with the very high daytime temperatures, weak synoptic winds and clear skies, a radiative surface cooling in excess of 10–15◦C was observed during the night at many locations throughout Iceland. The situation has been simulated with the Meso-NH model. The results indicate that katabatic winds develop in the stable nocturnal boundary layer when the cold and heavy air descends from the highlands and mountains down to lower lying areas. The simulations are made at a high horizontal and vertical resolution, forced with boundaries and initial conditions from the ECMWF. The simulations and initial conditions are compared to available ground based observations and satellite images showing the surface radiative temperature. The simulations seem to reproduce well most of the observed winds, including patterns where weak synoptic winds or katabatic flow interact with orography. The simulations also give valuable indications of locations of relatively strong katabatic winds, where no observations are currently available. A similar simulation has been performed with the MM5 atmospheric model and an intercomparison is under way.

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