Synergetic retrieval of aerosol from radiometer and lidar measurements coupled with radiosonde observations using GRASP algorithm

Abstract:

A synergetic aerosol retrieval from diverse combinations of ground-based sun-photometric measurements co-located with ground-based lidar and radiosonde observations using versatile GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm by Dubovik et al., [2011, 2014] is presented. Several aspects of observation synergy are considered.

First, a set of passive observations collected during day time and active observations collected during both day and night are inverted simultaneously under the assumption of temporal continuity of aerosol properties. Such approach explores the complementarity of the information in different observations and results in the robust and consistent processing of all observations. In the realized synergy retrievals, the information propagating from the close-by sun-photometric observations provides sufficient constraints for reliable interpretation of lidar observations, which usually suffer from the lack of information about aerosol particles sizes, shapes and complex refractive index.

Second, the synergetic processing of such complimentary observations with enhanced information content allows for optimizing the aerosol model used in the retrieval. Specifically, the external mixture of several aerosol components with pre-determined sizes, shapes and composition is proposed for achieving reliable retrieval of aerosol properties in several situations. This approach allows for consistent and accurate retrievals of aerosol from a combination of passive and active observations and also stable results from processing stand-alone lidar observations by reducing information content of aerosol columnar properties.

Third, the synergetic processing of the ground-based sun–photometric and lidar observations combined with in situ radiosonde scatterometer measurements using the data from KAUST.15 and KAUST.16 field campaigns held at King Abdullah University of Science and Technology in the August of 2015 and 2016 is studied. The inclusion of radiosonde data has been demonstrated to provide significant additional constraints to validate and improve the accuracy and scope of aerosol vertical profiling.

The results of all retrieval set-ups used for processing both synergy and stand-alone observation data sets are discussed and compared.