Quantifying turbulent coarse particle transport over drylands of Southeastern Iberia using a stand-alone Doppler lidar methodology

Abstract

Using a methodology for the estimation of coarse particle exchanges via Doppler lidar, based on the eddy covariance technique, profiles of vertical transport velocities were derived and analyzed. The methodology was tested across diverse atmospheric conditions in two different Mediterranean dryland landscapes in Southeastern Spain, namely Guadiana-UGR (extensive, inland olive grove), and Aguamarga (shrubland with maritime influence). Firstly, study cases were analyzed and the main atmospheric mechanisms impacting particle transport were identified. Convective mixing within the boundary layer was found to be the primary driver of the upward particle transport. However, cloud cover was observed to attenuate the transport velocity, while significant deposition events were observed during a Saharan dust outbreak. Secondly, positive transport velocities were found during convective periods and lower, yet positive, values during non-convective periods. Higher transport velocities were observed during a drier period at Guadiana-UGR, likely due to drier soil conditions. Aguamarga exhibited notably lower transport velocities. Considering only the lowermost observational level (105 m above the ground), net emission of particles was observed. Footprint analysis supported the representativeness of the fluxes. Our findings provide novel insights into particle exchanges over Mediterranean drylands, quantifying the turbulent transport and identifying its atmospheric drivers. Additionally, the considered ecosystems were found to be net sources of particles during the study periods. These results highlight the role of drylands as emerging contributors to global dust emissions in the context of climate change.