Hirlam och Harmonie. Fallstudie.

• Main Author: Söderberg, Sofia
• Format: Other/Unknown Material
• Language: Swedish
• Published: Lunds universitet/Fysiska institutionen 2012
• Subjects: meteorologi; Hirlam; Harmonie; väderprognos; prognos; prognosmodeller; icke-hydrostatisk modell; hydrostatisk modell; vertikal hastighet; primitiva ekvationer; väder; observationer; Physics and Astronomy; Greenland; Nuuk
• Online Access: http://lup.lub.lu.se/student-papers/record/2863002

Detailed weather predictions are of interest e.g. to protect humans and society from damages caused by extreme weather. To do this today’s forecast models need higher resolution, i.e. less distance between measure points. So-called non-hydrostatic models are used when this distance decreases. The development of this type of models has progressed during the past 20 years due to more powerful computers. Current hydrostatic model at the Danish Meteorological Institute, DMI, with highest resolution has got 3 km between its measure points. For more detailed, local forecats DMI are now considering a non-hydrostatic weather model, HARMONIE, to increase the resolution. It has not been proved that HARMONIE gives better results than the hydrostatic model, HIRLAM, and now the two models are run simultaneously at DMI to be compared. This report gives an account of the basis in today’s weather models and an insight in technical and mathematical differences between HIRLAM and HARMONIE. Vertical velocity which is diagnostic in a hydrostatic model and prognostic in a non-hydrostatic model is particularly studied. The report also describes the weather situation at Greenland from 27th of February 2012 until the 12th of March 2012 when it was extremely cold in that area. This is followed by a case studie for the Nuuk-area (Greenland) where 24-hours forecasts from HIRLAM and HARMONIE are compared with observations. Finally a summary of verifications (diagrams and tables) for the period 6th - 12th of March 2012 is given which shows that the prognosis from both models are approved. Changing to the HARMONIE-model over Greenland should therefore not effect the quality of the forecasts over land. However the model may be less accurate than HIRLAM for upper levels southwest of Greenland.