Turbulence Analysis in Long‐Range‐Transported Saharan Dust Layers With Airborne Lidar

In this study, turbulent properties of long‐range‐transported Saharan dust layers are investigated for the first time using airborne backscatter and water vapor lidar measurements. This is achieved via the utilization of spectral signal decomposition to the collected lidar data. Additionally, measurements by dropsondes are analyzed in detail. The presented measurements were conducted during the Next‐Generation Aircraft Remote Sensing for Validation Studies II in boreal summer 2016 upstream Barbados. An analysis of two case studies shows that the derived mesoscale turbulence cascades inside the transported dust layers follow the predicted slopes for turbulence of −5/3. The turbulent nature of the Saharan air layers (SALs) is additionally indicated by small Richardson numbers, which are derived from data collected by launched dropsondes. These presented results also fortify the hypothesis that turbulence inside dust layers helps to keep large mineral dust particles aloft for a longer time, so that they can still be found after long‐range transport. Plain Language Summary Each year great amounts of Saharan mineral dust particles get transported westwards over the Atlantic Ocean in elevated dust layers. However, it is still not fully understood why dust particles of large diameters (tens of microns) can still be found in the Caribbean. According to Stokes theory, they would already be deposited at the beginning of their transport. In this study, for the first time, spectral signal decomposition is applied on airborne lidar measurements of long‐range‐transported Saharan dust layers. In this way, it is shown that turbulence inside the dust layers is well established. As a reason, large dust particles remain in the atmosphere for a longer time and can potentially be transported this far away from their source region. Key Points First spectral analysis of airborne lidar data in long‐range‐transported Saharan dust layers Richardson numbers point toward mixing processes in Saharan dust layers Derived power spectra highlight established mesoscale turbulence cascade in dust layers