Abstract
Abstract. A severe windstorm downstream of Mt. Öræfajökull in Southeast Iceland is simulated on a grid of 1 km horizontal resolution by using the PSU/NCAR MM5 model and the Advanced Research WRF model. Both models are run with a new, two equation planetary boundary layer (PBL) scheme as well as the ETA/MYJ PBL schemes. The storm is also simulated using six different micro-physics schemes in combination with the MYJ PBL scheme in WRF, as well as one "dry" run. Output from a 3 km MM5 domain simulation is used to initialise and drive both the 1 km MM5 and WRF simulations. Both models capture gravity-wave breaking over Mt. Öræfajökull, while the vertical structure of the lee wave differs between the two models and the PBL schemes. The WRF simulated downslope winds, using both the MYJ and 2EQ PBL schemes, are in good agreement with the strength of the observed downslope windstorm. The MM5 simulated surface winds, with the new two equation model, are in better agreement to observations than when using the ETA scheme. Micro-physics processes are shown to play an important role in the formation of downslope windstorms and a correctly simulated moisture distribution is decisive for a successful windstorm prediction. Of the micro-physics schemes tested, only the Thompson scheme captures the downslope windstorm.
Highlights
Iceland is a mountainous island located in the middle of the North Atlantic Ocean in the northern part of the storm track
Mountain waves and downslope windstorms have long been a target of research campaigns as well as theoretical and numerical researches
The objective of this study is to investigate the differences in the simulated dynamics of the downslope windstorm that are caused by the differences in the dynamical cores of two mesoscale models (MM5 and WRF)
Summary
Iceland is a mountainous island located in the middle of the North Atlantic Ocean in the northern part of the storm track. The climate and weather of Iceland are largely governed by the interaction of orography and extra-tropical cyclones. This interaction can be in the form of cold air damming by mountains or warm downslope descent. The prime objective of the T-REX (Terrain-induced Rotor EXperiment) campaign (Grubišicet al., 2008) in Sierra Nevada was on observations of mountain waves, rotor flow and low- and upper-level turbulence. This was done by means of ground-based observations and state of the art remote sensors and airborne observing systems. A number of papers based on the observations of T-REX have emerged, e.g. Jiang and Doyle
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
