Seasonal range test run with Global Eta Framework

Abstract

Abstract. Global Eta Framework (GEF) is a global atmospheric model developed in general curvilinear coordinates and capable of running on arbitrary rectangular quasi-uniform spherical grids, using stepwise ("Eta") representation of the terrain. In this study, the model is run on a cubed-sphere grid topology, in a version with uniform Jacobians (UJ), which provides "equal-area" grid cells, and a smooth transition of coordinate lines across the edges of the cubed-sphere. Within a project at the Brazilian Center for Weather Forecasts and Climate Studies (CPTEC), a nonhydrostatic version of this model is under development and will be applied for seasonal prediction studies. This note describes preliminary tests with the GEF on the UJ cubed-sphere in which model performance is evaluated in seasonal simulations at a horizontal resolution of approximately 25 km, running in the hydrostatic mode. Comparison of these simulations with the ERA-Interim reanalyses shows that the 850 hPa temperature is underestimated, while precipitation pattern is mostly underestimated in tropical continental regions and overestimated in tropical oceanic regions. Nevertheless, the model is still able to well capture the main seasonal climate characteristics. These results will be used as a control run in further tests with the nonhydrostatic version of the model.

Seasonal climate and the onset of the rainy season in western‐central Brazil simulated by Global Eta Framework model

“…Some preliminary results with this version of the model were shown in Latinović et al . (), where the ability of GEF to perform simulations with increased horizontal resolution and upgraded version of cubed‐sphere and its stability in long‐term seasonal integrations were confirmed. The results shown here show high level of spatial correlation between the model simulations and the reanalyses for almost all analysed variables, with correlations of five out of six variables varying from 0.85 to 0.99.…”

“…The high computational demand of the spectral model for long‐term simulations limits the CPTEC global models to the coarse resolution of about 200 km. The GEF development at CPTEC for seasonal forecasts (Latinović et al ., ) is a less computationally demanding alternative for the operational seasonal forecasts at the centre.…”