Aproximation to the characterization of the spatio-temporal variability of clouds and aerosols in the Aburra Valley from satellital and ground-based remote sensing

The Aburrá Valley is a narrow complex mountainous terrain located in the Colombian Andes. In recent years this region has experienced critical air quality episodes, with daily concentrations reaching over 100 μg/m3. Meteorological and climate variability modulates the occurrence of these episodes. The presence of low-level clouds and the structure of the Atmospheric Boundary Layer (ABL) are critical factors for the understanding of the behavior of aerosols. Scanning LIDARS (Light Detection and Ranging devices) are versatile tools to assess ABL dynamics in an urban environment, allowing aerosol characterization and spatio-temporal evaluation. In this work, we study vertical profiles of attenuated backscatter and depolarization ratio derived from a ground-based scanning LIDAR, and simultaneous profiles obtained from the space-borne CALIOP Lidar instrument onboard CALIPSO satellite to characterize the spatio-temporal variability and structure of the Aburrá Valley ABL. The profiles are also contrasted with backscatter measurements from three lidar ceilometers operating within the valley. The results suggest that both ground-based remote sensors identify similar variability of the atmospheric vertical structure, aerosols, and ABL height. In the case of CALIPSO, we do not intend to validate or calibrate the retrievals using ground-based instruments; several authors have reported aerosol profile disagreements due to random and systematic sources. Instead, we consider CALIPSO and ground-based retrievals as complementary leading to a better understanding of the atmospheric profile, and the implications of aerosol-cloud interactions feedbacks for the surface radiative balance. While the amount of data is not yet sufficient for statistically significant conclusions, the preliminary aerosol and cloud characterization and discrimination allow the clustering of four cases with different consequences for incoming solar radiation and turbulent fluxes. The cases include (i) cloud-free and low aerosol load, (ii) cloud-free and high aerosol load, (iii) cloudy skies and low aerosol load, and (iv) cloudy skies and high aerosol load scenarios.