Abstract
A global spectral model is used to carry out a number of short to medium range prediction experiments with global datasets. The primary objective of these studies is to examine the formation and motion of the hurricanes/typhoons with a fairly comprehensive state-of-the-art global model. Ale spectral model utilizes the usual transform method for the calculations of the nonlinear and physical processes. The physical processes include parameterizations of the planetary boundary layer, deep and shallow cumulus convection, radiative processes (including cloud feedback processes, diurnal change and surface energy balance) and large-scale condensation. ‘Envelope orography’ is used to represent steep mountains globally. Ocean temperatures are prescribed from a Preceding 10 day averaged dataset for the storm periods under investigation.
Sensitivity of storm forecasts to horizontal and vertical resolutions, datasets and representation of physical processes are addressed in this paper.
The major findings of this study are that improved results on the formation and motion of storms are achieved in several cases when (i) the surface layer fluxes are adequately resolved, (ii) the final FGGE analyzed datasets are used, (iii) very high resolution in the horizontal (106 waves triangular truncation) is used, and (iv) improved physical parameterization for the boundary layer, cumulus convection and radiative process are included.
The major limitation of this study is that in spite of the use of very high resolution the inner rain area (radius<150 km from the storm center) is not adequately represented to describe the central pressure, maximum wind and the warm core of hurricanes. Further studies to improve these areas are suggested.
