Ten-year seasonal climate reforecasts over South America using the Eta Regional Climate Model.

Sin Chan Chou,Claudine Dereczynski,Jorge Luís Gomes,Ramiro Ruiz-Cárdenas,Nicole C Resende,Ana Maria H De Avila,Josiane Ferreira F Bustamante,José Fernando Pesquero,Carlos Renato De Souza,Luís Felipe Alves

doi:10.1590/0001-3765202020181242

Abstract

Ten-year seasonal climate reforecasts over South America are obtained using the Eta Regional Climate Model at 40 km resolution, driven by the large-scale forcing from the global atmospheric model of the Center for Weather Forecasts and Climate Studies. The objective of this work is to evaluate these regional reforecasts. The dataset is comprised of four-month seasonal forecasts performed on a monthly basis between 2001 and 2010. An ensemble of five members is constructed from five slightly different initial conditions to partially reduce the uncertainty in the seasonal forecasts. The seasonal mean precipitation and 2-meter temperature forecasts are compared with the observations. The comparison shows that, in general, forecasted precipitation is underestimated in the central part of the continent in the austral summer, whereas the forecasted 2 meter temperature is underestimated in most parts of the continent and throughout the year. Skill scores show higher skill in the northern part of the continent and lower skill in the southern part of the continent, but mixed skill signs are seen in the central part of the continent. During the El Niño and La Niña seasons, the forecast skill scores clearly increase. The downscaling of the Eta model seasonal forecasts provides added value over the driver global model forecasts, especially during rainy periods.

Highlights

The information derived from seasonaltimescale climate predictions is extremely relevant for planning actions in various sectors of society, in the energy sector, where seasonal rainfall forecasts could support activities related to the generation, transmission, and distribution of energy
The objective of this work is to evaluate the seasonal forecasts from the Eta Regional Climate Model over the South and Central American regions
The model was operational at the National Centers for Environmental Prediction (Black 1994) and became operational at the end of 1996 at the Center for Weather Forecasts and Climate Studies (CPTEC) of the Brazilian National Institute for Space Research (INPE) (Chou 1996)

Summary

Introduction

The information derived from seasonaltimescale climate predictions is extremely relevant for planning actions in various sectors of society, in the energy sector, where seasonal rainfall forecasts could support activities related to the generation, transmission, and distribution of energy. Seasonal forecasts from global climate models (GCMs) generally provide information at resolutions that are still too coarse for planning or for taking actions at a local scale. The application of dynamical downscaling (Laprise et al 2000) may provide more detailed information for seasonal climate impact studies. In the dynamical downscaling technique, a regional climate model (RCM) is nested into a GCM. The global model provides the initial, lateral and lower boundary conditions, which contain information about the large-scale atmospheric circulation. The higher resolution of the RCMs allows more robust circulation and a better description of the surface conditions, which provides added value over the driver coarse resolution model simulations (Laprise et al 2008)

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Conclusion