Easterly waves and precipitation over northern South America and the Caribbean

Abstract

ABSTRACTThe Easterly Waves (EWs) have been highlighted as one of the different spatiotemporal processes that influence hydro‐climatology over northern South America and the Caribbean Sea, particularly during boreal summer. Previous studies recognize the EWs among the most important features of the rainy season in northern South America, suggesting the occurrence of precipitation as the main meteorological response to the passage of these disturbances. However, it is shown in this work that not all the EWs that propagate over northern South America and the Caribbean Sea have such an effect. Almost 50% of the EWs moving over the region during the 1983–2018 period were accompanied by the inhibition of precipitation and clear skies, as depicted by anomalies from the Climate Data Record of Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks precipitation dataset and the National Oceanic and Atmospheric Administration interpolated Outgoing Longwave Radiation dataset. This work intends to address the relationship between these atmospheric perturbations and the occurrence or inhibition of precipitation, as well as a plausible connection with the Madden–Julian Oscillation (MJO). In particular, horizontal components of wind and relative vorticity, together with low and upper troposphere divergence, were used to identify and characterize the EW activity over northern South America and the Caribbean Sea. Results suggest an influence of the MJO on the effects that the EWs have on convection and precipitation over the region, as well as the direction in which such perturbances continue their westward propagation.