Doppler lidar observations of low-level jets and wind maxima over urban complex terrain in the southeastern Iberian Peninsula

This study provides a detailed characterization and classification of low-level wind maxima (LLWmax) and the first instrumental observations of low-level jets (LLJs) in Granada, a Mediterranean city with complex terrain. Two Doppler lidar datasets were analyzed, one spanning seven years and another with a larger vertical range covering one year. LLWmax and LLJs were detected using an automated algorithm and classified via K-means clustering, identifying seven consistent clusters in both datasets. About 70 % and 57 % of LLWmax occurrences in each dataset are driven by local atmospheric boundary layer (ABL) dynamics, represented by three clusters. Three other clusters relate to Saharan Air Layer intrusions, distinguished by high wind speeds, elevated jet noses, or longer durations. The final cluster corresponds to gap winds from dust intrusions channeled through valleys. The most predominant cluster corresponds to LLJs matching the inertial oscillation mechanism of Blackadar. LLJs form more often during warm months, influenced by synoptic forcing, topography, and turbulence decay from the prior day. Microwave radiometer data indicate LLJ development is frequently accompanied by temperature inversions, while ceilometer signals suggest a cleansing effect above the LLJ core but an accumulation of aerosols beneath it. These findings highlight distinct LLJ formation processes and emphasize the need for further observations in urban complex terrain to improve LLJ understanding. Better knowledge of LLJs can aid air quality management during pollution episodes. • Long-term Doppler lidar data reveal distinct LLWmax types over complex urban terrain. • LLJs consistent with Blackadar theory have been observed in this study. • Upper-level pressure gradients drive LLJ intensity and height. • Turbulence decay before sunset influences next-night LLJ wind maxima. • LLJs enhance upper-air dispersion but trap pollutants near the surface under inversions.