Vertical distribution of Saharan dust and radiative forcing over the northern tropical Atlantic

Dust storms from Africa happen frequently over the northern tropical Atlantic. Advection of desert boundary layer air over the moist marine layer, termed as the Saharan Air Layer (SAL), is characterized by a dry and dusty mid-level warm anomaly. Although it is well established that dust aerosols have an important impact on the Earth's radiation budget through absorbing and scattering visible and infrared radiation, modeling the radiative forcing remains a challenge due to the uncertainty in the vertical distribution of dust. Therefore, it is necessary to quantify the vertical distribution of dust in order to better understand surface to top of the atmosphere forcing. In this work we present a spatially explicit monthly Atlantic climatology of the vertical profile of dust aerosols using data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) from June 2006 through August 2011 at a vertical resolution of 30m. We compare our remotely sensed vertical dust climatology to output from aerosol transport models, showing positive (upward) biases in the modeled dust profiles. We also quantify the influence of dust vertical biases in a modeling environment on direct radiative forcing by the mineral aerosols at the surface and the top of the atmosphere. Our results suggest that accurate vertical representation of dust over the Atlantic is relevant to understanding the influence of these mineral aerosols on the regional climate.