Abstract
This work evaluates the Lidar-Radiometer Inversion Code (LIRIC) using sun-sky photometers located at different altitudes in the same atmospheric column. Measurements were acquired during an intensive observational period in summer 2012 at Aerosols, Clouds, and Trace gases Research InfraStructure Network (ACTRIS)/Aerosol Robotic Network (AERONET) Granada (GRA; 37.16°N, 3.61°W, 680 m above sea level (a.s.l.)) and Cerro Poyos (CP; 37.11°N, 3.49°W, 1820 m a.s.l.) sites. Both stations operated AERONET sun-photometry, with an additional lidar system operating at Granada station. The extended database of simultaneous lidar and sun-photometry measurements from this study allowed the statistical analysis of vertically resolved microphysical properties retrieved with LIRIC, with 70% of the analyzed cases corresponding to mineral dust. Consequently, volume concentration values were 46 μm3/cm3 on average, with a value of ~30 μm3/cm3 corresponding to the coarse spheroid mode and concentrations below 10 μm3/cm3 for the fine and coarse spherical modes. According to the microphysical properties’ profiles, aerosol particles reached altitudes up to 6000 m a.s.l., as observed in previous studies over the same region. Results obtained from comparing the LIRIC retrievals from GRA and from CP revealed good agreement between both stations with differences within the expected uncertainties associated with LIRIC (15%). However, larger discrepancies were found for 10% of the cases, mostly due to the incomplete overlap of the lidar signal and/or to the influence of different aerosol layers advected from the local origin located between both stations, which is particularly important in cases of low aerosol loads. Nevertheless, the results presented here demonstrate the robustness and self-consistency of LIRIC and consequently its applicability to large databases such as those derived from ACTRIS-European Aerosol Research Lidar Network (EARLINET) observations.
Highlights
Atmospheric aerosol particles affect the Earth’s atmosphere system directly by scattering and absorbing solar radiation and indirectly by acting as cloud condensation and ice nuclei, modifying cloud properties
Τ440 nm presented larger values above GRA, since a larger atmospheric column was measured, and it was affected by the local aerosol sources from the city, whereas the Cerro Poyos (CP) site is a remote site usually above the atmospheric boundary layer (ABL) of the city of Granada
In most of the cases, values were very close, indicating that most of the aerosol load was located above the CP altitude and typically associated with the presence of advected aerosol layers above 1820 m a.s.l
Summary
Atmospheric aerosol particles affect the Earth’s atmosphere system directly by scattering and absorbing solar radiation and indirectly by acting as cloud condensation and ice nuclei, modifying cloud properties. These networks only provide column-integrated aerosol optical and microphysical properties Aerosol lidar networks such as GALION (Global Atmospheric Watch Aerosol Lidar Observation Network) and its participant networks, i.e., EARLINET (European Aerosol Research Lidar Network, www.earlinet.org) [4], MPLNET (Micro Pulse Lidar Network) [5], LALINET (Latin American Lidar Network [6,7]) or ADNET (Asian Dust Network) [8], provide vertically resolved aerosol properties, overcoming this drawback. This potential of the lidar technique serves to advance estimations of aerosol radiative properties [9,10]. Inferring aerosol microphysical properties from lidar measurements alone requires complex inversion algorithms (e.g., [11,12,13]) and is only possible if the particle backscatter coefficient is measured at three wavelengths (typically 355, 532 and 1064 nm), particle extinction coefficient at two wavelengths (typically, 355 and 532), and strict constraints are applied to the inversion (e.g., [14])
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