Comparison of diurnal aerosol products retrieved from combinations of micro-pulse lidar and sun-photometer over KAUST observation site

Abstract. This study focuses on comparison of aerosol columnar AOD and Lidar Ratios together with vertical profiles of aerosol extinction and backscatter at 532 nm retrieved over the King Abdullah University of Science and Technology (KAUST) campus observation site for a period of 2019–2022 using GRASP and MPLNET approaches. An emphasis is made on independent analysis of daylight and nighttime retrievals to estimate how strongly the differences in assumptions of both methods made in absence of nighttime AOD observations influence the retrieval results. Additionally, two aerosol products provided by GRASP excluding and including the volume depolarization observations at 532 nm provided by MPLNET are analyzed to estimate the potential benefits of usage of depolarization data in aerosol profile retrievals. In overall, both columnar and vertical MPLNET and GRASP products demonstrated a better agreement for day-time retrievals for the GRASP product excluding the depolarization information. At the same time, inclusion of the volume depolarization observations improved the agreement between MPLNET and GRASP estimated values at nighttime, both columnar and vertical. In addition, estimated values of daytime extinction profiles at a ground level were compared to assess the impact of assumptions of constant aerosol vertical distribution in the cut-off zone of lidar observations implied in GRASP. The values estimated by GRASP demonstrated a good agreement with MPLNET, both for retrievals including and excluding volume depolarization information. A seasonal variability of diurnal cycle of aerosol properties estimated by GRASP over KAUST site for the period 2019–2022 is presented, analyzed and discussed.

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