Consistency of the Single Calculus Chain Optical Products with Archived Measurements from an EARLINET Lidar Station

Kalliopi Artemis Voudouri,Nikolaos Siomos,Giuseppe D’Amico,Ina Mattis,Dimitris Balis,Konstantinos Michailidis

doi:10.3390/rs12233969

Abstract

A long-term analysis and climatology of aerosol backscatter and extinction coefficients profiles using a five-year study period lidar dataset derived from a multiwavelenth Raman lidar at Thessaloniki station is presented. All measurements have been processed with the latest version of the Single Calculus Chain (SCCv5.1.6) fully automated algorithm, which has been developed to provide a common lidar processing tool, within EARLINET (European Aerosol Research Lidar NETwork) stations. The optical products delivered by the SCC tool have already been compared with the optical products derived from the operational algorithm of Thessaloniki (THessaloniki Aerosol LIdar Algorithm-THALIA) and discussed in terms of inhomogeneities. In this contribution, we analyze these products for climatological purposes, in order to investigate the aerosol columnar properties over Thessaloniki lidar station, drawing conclusions about the issues to be considered when switching from the current operational algorithm to the SCCv5. The SCCv5 algorithm is evaluated for the AOD both for 355 and 532 nm. The agreement with THALIA algorithm seems promising with correlations of 0.89 and 0.84, respectively, and absolute deviations within the range of the EARLINET quality requirements. Time series of the AOD at 355 nm denote a decrease of 0.017 per year in the free troposphere, a trend that is also shown in the AOD values derived from the operational algorithm (0.014). A decrease of 0.01 per year in the lower troposphere is also noted from the SCC, whereas the corresponding AOD values derived from the operational algorithm denote a decrease of 0.017.

Highlights

Active remote sensing instruments such as lidars are widely used for the vertical profiling of aerosols, providing two undoubtable advantages in the monitoring of atmospheric features, namely the vertical and temporal resolution
We demonstrate the capability of Remote Sens. 2020, 12, 3969 the automated algorithm developed within EARLINET network to provide climatological products and we identify the issues to be considered when switching from the current operational algorithm (THessaloniki Aerosol LIdar Algorithm (THALIA)) to the Single Calculus Chain (SCC)
The results for two case studies and the climatological analysis of the aerosol optical properties based on the SCCv5 retrievals are presented

Summary

Introduction

Active remote sensing instruments such as lidars are widely used for the vertical profiling of aerosols, providing two undoubtable advantages in the monitoring of atmospheric features, namely the vertical and temporal resolution. The increased availability of lidar intensive parameters (e.g., the wavelength dependence of extinction and/or backscatter coefficients, extinction-to-backscatter (lidar) ratio and particle depolarization ratio at one or more wavelengths) is important to infer different aerosol types and their mixtures, as is discussed in many papers [3,4,5,6], and can lead to accurate aerosol classification. Another important aspect in the study of aerosols on a global scale is the need for increased spatial coverage. Two important aspects were considered among the EARLINET stations: the necessity of a common processing tool in order to assure the homogeneity of the products among network datasets as well as the need of short-time availability of the data, as the high-quality manual lidar data analysis usually requires both time and manpower

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