Network activity 4:

Standardised measurement protocols, intercomparisons and quality assurance for optical properties of aerosols

Objectives and expected impact

The overall objective of Networking Activity NA4 is to integrate and harmonise measurements of aerosol optical properties at the EUSAAR sites, with the outcome of having a sustainable and reliable observation network for aerosol optical data across Europe with known and high quality, and that is readily accessible in a common format.

This requires the development of standard procedures for routine measurements of optical parameters (aerosol scattering coefficients, aerosol absorption coefficients and aerosol optical depth). Because of different types of instruments used, of different make, it is difficult for the users to assess the quality of the data from the various stations.

Objective 1

Develop a protocol providing aerosol optical measurements to ensure that they all will adhere to a schedule of regular calibration and quality assurance for the relevant instruments and make data available on-line in a common format.

Objective 2

Develop calibration procedures for the various instruments at the EUSAAR sites for measurements of aerosol scattering and absorption coefficients and aerosol optical depth.

Objective 3

Develop QA procedures to determine accuracies and uncertainties for the instrumentation and data on aerosol optical properties at the EUSAAR sites.

Objective 4

Harmonise aerosol optical property data bases which are accessible via a single webpage.

Description of work

The tasks to meet these objectives are:

• Intercomparison and calibration of instruments used to measure aerosol scattering coefficients. This will involve a calibration workshop at the WCCAP (World Calibration Center for Aerosol Physics, IFT, partner 6) and technical training (with NA6). A procedure will be developed for on-site calibration involving a travelling standard.


• Intercomparison and calibration of absorption photometers. This will involve a calibration workshop at the WCCAP and technical training (with NA6). Procedures will be developed for on-site calibration involving a travelling standard.


• Intercomparison of instruments providing aerosol optical depth (AOD). Few of the EUSAAR sites are part of the AERONET using CIMEL sun photometers, but the other sites use other instruments, such as the Precision Filter Radiometer used in the WMO-GAW Network. To harmonise the data from all EUSAAR sites, calibration and intercomparison are proposed at the World Optical depth Research and Calibration Centre (WORCC) in Davos.


• Development of a protocol involving a number of checks that regularly need to be performed, such as cleaning of optical surfaces, battery checks and data check procedures to ensure that instrumentation works properly and data are of the best possible quality. This includes regular instrument calibration and regular inspection of the instruments.


• Development of common procedures for optical measurements and data processing to account for differences due to temperature and relative humidity (RH) effects on the extinction and absorption coefficients.


• Implementation of the on-site calibration, quality assessment, protocols and procedures at each EUSAAR site.