Numerical simulation of the circulation and tropical teleconnection mechanisms of a severe drought event

Large domains in regional climate models are known to provide a better representation of the mesoscale circulation and hence the precipitation field. To evaluate the model performance in reproducing the tropical circulation as well as the severe drought event (2012-2016) in the northeastern Brazil, simulations for the 2012-2016 period were performed using the tropical band version of the Regional Climate Model (RegT-Band). The RegT-Band simulation were driven by the ERA-Interim data for the initial and lateral boundary conditions and sea surface temperature was obtained from NOAA_OISST_V2 reanalysis. The domain covers the entire tropical belt between 30°S and 30°N with grid spacing of about 30 km. Results showed that the general features of the tropical circulation and associated precipitation pattern over the entire domain are well captured by the model compared to the observations. However, systematic biases, mainly related to the double ITCZ bias are observed, which provide an unrealistic peak of double precipitation outside the equator and insufficient precipitation at the equator. In the NEB subdomain, RegT-Band shows weakness and significant model error to represent the subregion where the drought event was more severe. However, the model satisfactorily represents the precipitation anomalies in the driest years. Therefore, this study shows results encouraging the use of RegT-Band to study extreme events associated with droughts conditions in the Northeastern Brazil.