A regional ensemble forecast system for Southeastern South America: preliminary assessment

RUIZ, J.; C. SAULO; E. KALNAY

Foz do Iguazú, Brasil

Congreso; 8th International Conference on Southern Hemisphere Meteorology and Oceanography; 2006

American Meteorological Society

The main objective of this study is to asses the skill of a short range regional ensemble forecast system over Southeastern South America. The proposed regional ensemble forecast system consists of 9 members: 4 pairs of perturbed forecasts plus a control forecast. The initial and boundary conditions are perturbed using scaled lagged forecasts (SLAF) from the Global Forecast System operational runs. These perturbed initial and boundary conditions are used to run a 9-regional forecast ensemble, using WRF V2.0 mesoscale model. The skill of the ensemble mean is compared against the skill of the control forecast.  Also, in order to investigate if the ensemble dispersion could be used to forecast the magnitude and distribution of the control forecast errors, the relationship between these variables is measured over the region. The root mean squared error between the forecasted fields and the analysis is computed as a function of forecast times in order to asses the skill of both the ensemble and the control forecasts. When available, upper air observations are also used in a similar way. Results suggest the benefit of adopting an ensemble technique to improve regional forecasts. The verification of other ensemble derived products as the probabilistic quantitative precipitation forecast over this region, and implementation of other methods to generate initial condition perturbations are important issues to be addressed in future work.