Saharan Dust Transport towards the Tropical Atlantic Ocean and South America: A 3-Dimensional Analysis based on Livas Aerosol Climatology

Abstract

Understanding the spatial distribution of aerosol particles is essential to evaluating their influence on the climate system. Saharan dust plume as a fundamental component of the global aerosol system requires a comprehensive analysis of its spatial structure. The main objective of this research was to study the Saharan dust plume structure over Mindelo City, in Cabo Verde, and during its transport towards remote areas of tropical Atlantic and Americas using the recently developed LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies (LIVAS), a 3-D multi-wavelength global aerosol optical database based on CALIPSO satellite products. LIVAS products' dependence on the radius used to aggregate CALIPSO profiles was also evaluated. A preliminary comparison of daily and monthly scales of the backscatter and extinction coefficient profiles between LIVAS and PollyXT, a ground-based lidar system operated at Mindelo City, indicated a good agreement. The application of LIVAS columnar and vertical optical properties products to characterize the seasonal variability of Saharan dust transport over Mindelo shows that most of the dust transported occurs from June to September and has a maximum of 2 to 5 km. During the winter season, from December to January, aerosol loading in the free troposphere is dramatically reduced, and most of the dust is transported within the (MBL,) in a layer up to ~2.5 km. Dust mean contribution to the backscatter profile during summer varied from ~90% in the free troposphere to less than 25% in the MBL. In the winter, the contribution in the free troposphere is reduced to less than 50%. Regarding the dependence on the aggregation radius, the main dependence found was for monthly (DOD), with smaller radii (<200 km) producing lower climatological values when compared with larger radii. The LIVAS application, which describes the seasonal transport of Saharan dust to remote western areas of the tropical Atlantic and Americas, also depicted patterns that are consistent with previous studies. The magnitudes of dust transport, as identified by the extinction coefficient profile are highest in boreal summer and spring and lowest in autumn. The northward shifts of the dust plume are further during the summer, reaching the latitude of 25oN. This displacement is mainly modulated by the seasonal migration of the (ITCZ), and it leads to the transport of dust toward Central America and the Caribbean. Winter is the season that the lowest amount of dust arrives in the remote western tropical Atlantic and South America, which can be explained by the low-level transport of dust and the efficient removal of dust along its way.