AOD differences analysis Prede-PFR-Cimel on a 11 years dataset at Meteorological Observatory Lindenberg

Photometers are the most accurate instruments to retrieve the aerosol optical depth (AOD) for a given spectral channel (e.g. 500 nm). There are three main networks of photometers: GAW-PFR (Global Atmosphere Watch - Precision Filter Radiometer) using the instrument PFR (Precision Spectral radiometer), AERONET (AErosol RObotic NETwork): AOD and aerosol properties measurements network using Cimel CE-318 photometer, and SkyNet (SKY Measurements NETwork), using the instrument Prede POM (Precise design Of Meteorological). These three networks use different instruments, different measurement methods, different calibration methods and different retrieval methods algorithms).

The Meteorological observatory Lindenberg (MOL-RAO) from German meteorological service (Deutscher Wetterdienst: DWD) in Lindenberg (Tauche, Germany) is the only site worldwide operating permanently the three instruments of these three networks. There is a dataset of 11 years (since 2013) of colocated and synchronized AOD measurements of GAW-PFR, AERONET, SKYNET photometry networks at this station.

In this study, supported by COST action HARMONIA and initiated at the COST HARMONIA training school “Sky over BerLin”, we quantify the differences in the AOD from the products of these three different networks, we investigate the sources of these differences, computing the corrections on the optical depth (rayleigh, ozone, NO2) regarding amount of components consider in inputs of the retrieval algorithm and the equation used by the algorithm to consider these corrections. Analizing the temporal and  air mass dependences o the differences and analyzing which differences are artificial (different way of computing with different inputs or equations during the retrievals) or inherent to the measurement itself (instrumental difference, calibration issues).