Atmospheric stratification over the Southeast Atlantic Ocean adjacent to the Namibian coast

Abstract. Atmospheric stability, characterised by absolutely stable atmosphere and temperature inversions, is a prominent feature of atmospheric stratification over the Namibian coast and the adjacent Southeast Atlantic (SEA) Ocean. This stratification plays a critical role in the transport and distribution of atmospheric pollutants, energy, momentum, and other physical components. Key factors influencing the vertical structure of the atmosphere include the South Atlantic High and transient baroclinic westerlies, 5 which drive ocean-subcontinent heat exchange, a dominant factor in the formation of inversions and atmospheric stability. Observations from ERA5 reanalysis data and global positioning system radio occultation (GPS-RO) measurements over 11 years (2007–2017) reveal that low-level inversions are more frequent over the Namibian coastal regions and adjacent oceans compared to the subcontinent. This predominance is attributed to higher atmospheric stability, linked to ocean-atmosphere heat interactions driven by the cold Benguela western boundary current. Surface inversions exhibit a seasonal pattern, mostly peaking during winter. Moreover, winter is associated with a generally lower inversion base height (h_ib), while summer favours elevated-based (EL) inversions. Interestingly, inversions are strongest during the last part of winter and weakest in autumn, with typical depths ranging from 10 to 125 hPa and strengths between 3 °C and 9 °C. These inversions exhibit a significant association with the conditions that may support the formation of stratocumulus clouds, often occurring nearer to the surface within the planetary boundary layer (PBL).