Understanding EC-EARTH winter mean precipitation over the tropical Pacific: implications for prediction skill

Abstract

This study investigates the seasonal variability of convective precipitation (cPCP) and stratiform precipitation (sPCP) in the tropical Pacific, using hindcasts from the European Community Earth System model (EC-EARTH). Our analysis revealed that cPCP is primarily driven by sea surface temperature (SST), with warmer SSTs leading to increased convective activity. In contrast, thanks to its correlation with SST and also surface solar radiation downwards, results indicate sPCP is more influenced by atmospheric processes. sPCP and cPCP correlation is positive throughout all the tropical Pacific region although, their correlation is negative in the eastern Intertropical Convergence Zone (ITCZ). This region has been studied in detail considering the correlation between the different types of precipitation and the surface latent heat flux (LHF). It has been concluded that in the eastern ITCZ, LHF contributes to increase cPCP rather than sPCP, explaining the negative correlation between them. The study also highlights the limitation of observational data, which usually only provides total precipitation, thereby restraining the ability of the model to predict each precipitation component accurately. Our findings emphasise the possibility for separating precipitation data into cPCP and sPCP to improve model skill by computing the potential predictability of both components