Višemodelna ansambl metoda (MME) za prognozu putanja ciklona preko Sjevernoindijskog mora

A multimodel ensemble (MME) technique for predicting track of tropical cyclones over the North Indian Sea has been proposed. The technique is developed applying multiple linear regression procedure. Parameters of the ensemble technique are determined from the forecast datasets on the tracks of tropical cyclones over the North Indian Sea during the year 2008-2009. The parameters selected as predictors are: forecast latitude and longitude positions at 12-hour interval up to 72-hours forecast of five operational numerical weather prediction models. The dynamical models included for development of the ensemble technique are: (i) forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF), (ii) the National Centers for Environmental Prediction Global Forecast System (NCEP), (iii) the MM5 model, (iv) the Quasi-Lagrangian model (QLM) and (v) the model of Japan Meteorological Agency (JMA). A collective bias correction is included in the ensemble technique in which a multiple linear regression based minimization principle for the model forecast position against to the observed position is applied. These bias factors are described by separate weights at every 12-hours interval up to the 72-hour forecasts for each of the member model. When the technique is tested with the independent samples, forecast skill of the MME technique is found to be reasonably good. The average error ranges from of the order of 74 km to 290 km for forecasts up to 72-hour. Performance of the MME technique shows that there are skill improvements up to 30 km for the position errors over the best model at 72-hour forecast. The forecast skill of the MME technique for forecasts up to 72-hour also shows an improvement as compared to the forecasts from member models and the simple ensemble mean (ENM).U ovom radu predlaže se metoda za višemodelnu ansambl prognozu (MME) putanja tropskih ciklona nad sjevernim dijelom Indijskog oceana korištenjem prognoza nekoliko različitih modela. Metoda je razvijena na temelju višestruke linearne regresije. Parametri MME metode određuju se pomoću prognoziranih podataka putanja tropskih ciklona nad sjevernim dijelom Indijskog oceana u razdoblju 2008.–2009. Odabrani parametri su: prognozirana zemljopisna širina i dužina položaja ciklona u 12-satnom intervalu u 72-satnoj prognozi za pet operativnih numeričkih prognostičkih modela. Korišteni članovi ansambla u MME metodi su: (i) prognoze Europskog centra za srednjoročne prognoze vremena (ECMWF), (ii) prognoze Nacionalnog centra za zaštitu okoliša prognostičkog globalnog sustava (NCEP), (iii) MM5 model, (iv) kvazi-Lagrangian model (QLM) i (v) model Japanske meteorološke agencije (JMA). Koristeći višestruku linearnu regresiju između opaženih i modelima prognoziranih putanja, predložena metoda uključuje i smanjenje sveukupne srednje pogreške. Odgovarajući čimbenici odstupanja opisuju se odvojenim te šinama u svakom 12-satnom intervalu u cijeloj 72-satnoj prognozi za svaki pojedini model. Nakon testiranja metode na nezavisnim uzorcima pokazalo se da je uspješnost prognoze MME metodom zadovoljavajuća. Srednja pogreška je za 72-h prognoze unutar intervala od 74 km do 290 km. Performanse MME metode pokazuju da je poboljšanje uspješnosti do 30 km prilikom određivanja pogreške pozicije ciklone za najbolji model unutar 72-satne prognoze. Uspješnost prognoze pomoću MME metode za prognoze do 72-sata tako|er pokazuju poboljšanje u usporedbi s prognozama kako svakog pojedinačnog modela, tako i s prognozom temeljenom na jednostavnom srednjaku ansambla