Sensitivity of a long-range numerical weather forecast model to small changes of model parameters
- 1Chair of Physical Geography, Faculty of Sciences, University of Novi Sad, Trg D. Obradovića 3, 21000 Novi Sad, Serbia
- 2Hydrometeorological Service of Serbia, Kneza Višeslava 66, 11000 Belgrade, Serbia
- 3National Centres for Environmental Predictions, Washington, USA
Abstract. Sensitivity of extended-range numerical weather forecasts to small changes of model parameters is studied for two cases. In the first case the Earth radius was perturbed. In the other case changes of the gravity were introduced. The results for the 500 hPa geopotential fields are presented on hemispheric maps and intercompared visually and using RMS differences of the perturbed and reference forecasts. During about the first 10 days of integration the results indicate modest sensitivity of the forecasts to the parameter variation. After this period the forecasts diverge rapidly and start to differ significantly. Repeated integrations on the same computer using the same model setup and the same initial conditions yield identical results.