Evaluating the Thermodynamic Structure of Saharan Air Layer Events Using the Galvez‐Davison Index

Abstract The Saharan Air Layer (SAL) is a warm, dry, and stable air mass that carries millions of tons of dust annually, disrupting otherwise intense convection in the tropical North Atlantic Ocean. Because the SAL is a statically stable air mass, convective instability parameters can help identify the presence of a SAL event, though most convective indices are designed for forecasting mid‐latitude convection, and struggle when applied to more barotropic settings. The Galvez‐Davison Index (GDI) was developed to improve the skill of traditional instability metrics in tropical latitudes, accounting for thermodynamic factors that both enhance and inhibit tropical convection. This study uses a pre‐established data set of SAL events to evaluate their thermodynamic structure and evolution by leveraging the GDI as a proxy for convective instability. The GDI was calculated for 45 years of MERRA‐2 reanalysis over the tropical North Atlantic. GDI characteristics near SALs were found to reflect the known intra‐SAL stability patterns, though they also reveal large spatial and temporal variations. The most apparent pattern discovered was that intra‐SAL GDI was lowest at the end of the SAL's life cycle, which most frequently occurs in or around the Caribbean Sea. This eastward displacement of minimum GDI relative to maximum dust transport suggests that the strongest convective suppression occurs after prolonged exposure to SAL‐modified air rather than at the time of highest dust concentration or transport. Specifically, the lag in GDI decline following the SAL passage can assist in evaluating total air mass modifications in the wake of a SAL.