Rewriting the Climatology of the Tropical North Atlantic and Caribbean Sea Atmosphere

Abstract The Jordan mean tropical sounding has provided a benchmark reference for representing the climatology of the tropical North Atlantic and Caribbean Sea atmosphere for over 50 years. However, recent observations and studies have suggested that during the months of the North Atlantic hurricane season, this region of the world is affected by multiple air masses with very distinct thermodynamic and kinematic characteristics. This study examined ∼6000 rawinsonde observations from the Caribbean Sea region taken during the core months (July–October) of the 1995–2002 hurricane seasons. It was found that single mean soundings created from this new dataset were very similar to C. L. Jordan’s 1958 sounding work. However, recently developed multispectral satellite imagery that can track low- to midlevel dry air masses indicated that the 1995–2002 hurricane season dataset (and likely Jordan’s dataset as well) was dominated by three distinct air masses: moist tropical (MT), Saharan air layer (SAL), and midlatitude dry air intrusions (MLDAIs). Findings suggest that each sounding is associated with unique thermodynamic, kinematic, stability, and mean sea level pressure characteristics and that none of these soundings is particularly well represented by a single mean sounding such as Jordan’s. This work presents three new mean tropical soundings (MT, SAL, and MLDAI) for the tropical North Atlantic Ocean and Caribbean Sea region and includes information on their temporal variability, thermodynamics, winds, wind shear, stability, total precipitable water, and mean sea level pressure attributes. It is concluded that the new MT, SAL, and MLDAI soundings presented here provide a more robust depiction of the tropical North Atlantic and Caribbean Sea atmosphere during the Atlantic hurricane season and should replace the Jordan mean tropical sounding as the new benchmark soundings for this part of the world.