Historical trends in the trade wind inversion in the tropical North Atlantic Ocean and Caribbean

The trade wind inversion (TWI) serves as an important stabilizing mechanism in the tropical North Atlantic (TNA) region, including the Caribbean basin. Previous studies have diagnosed the TWI using in situ observations and radiosondes, typically over tropical islands. However, studies relying on these point measurements are unable to discern the climatology and evolution of the TWI over the rest of the TNA. This study addresses this gap in the literature through the use of high-resolution ERA5 reanalysis model level data. Due to the advances in the ERA line of reanalysis products, ERA5 now provides vertical level resolution as fine as similar to 4 mb in the lower troposphere, enabling the identification of shallow inversions, such as the TWI, consistently on a climatological time scale in remote regions of the world. While still coarser than observed soundings, this reanalysis-based approach provides a first attempt in understanding TNA TWI variability and its strength and frequency trends from 1979 to 2019. The TWI climatology constructed here finds consilience with previous modelling and observational studies in terms of the spatial variability of the TWI base and strength across this domain. Stronger and more frequent TWIs are noted across the central TNA across all seasons. Results from a Mann-Kendall analysis reveals increasing trends in TWI frequency and strength that vary spatially across the domain based on season. The most widespread and strongest increasing TWI frequency and strength signal is over the central TNA from December to July. Due to the regionalization of trends noted, potential regional forcing mechanisms responsible for these changes are discussed.