Examining Mid-Level Stable Layers Over the Tropical Atlantic during ORCESTRA

Abstract

Here we investigate elevated stable layers that frequently appeared at an altitude near 6 km in soundings obtained during the ORCESTRA field campaign. This observation deviates from the existing literature, which emphasizes that tropical mid-level stable layers are collocated with the 0°C level at ~4-5 km. Our analysis demonstrates a strong relationship between mid-level stability and the change in relative humidity across the stable layer (decreasing upwards). Mechanism-denial tests with an infrared radiative transfer model support the hypothesis that vertical changes in relative humidity are sufficient to drive the formation of mid-level stable layers through differential radiative heating. We compare the frequency and strength of these stable layers to those in other ocean basins utilizing data from other field campaigns. These comparisons highlight the correlation between vertically decreasing relative humidity and enhanced stable layers, as well as the frequency of stable layers above the 0°C level across ocean basins.