The overall mission of the ACTRIS Centre for Aerosol Remote Sensing (CARS) is described here:

ACTRIS-Switzerland contributes to CARS through the World Optical Depth Research and Calibration Center (WORCC), which is a section within the World Radiation Center at the Physikalisch-Meteorologisches Observatorium Davos (PMOD/WRC). WORCC is recognized by the WMO as the primary WMO reference center for aerosol optical depth measurements. One of the WORCC mandates is to support and lead homogenization activities among different aerosol optical depth (AOD) networks and to contribute towards worldwide AOD harmonization initiatives.

Based on the ACTRIS implementation plan (2020-2024) that defines the need of ACTRIS/CARS traceability towards WORCC standards, WORCC collaborates with the Center for Aerosol Remote Sensing (CARS) by permanently establishing WORCC precision filter radiometers (PFR) reference instruments at the three main ACTRIS/CARS Automatic Sun Photometer (ASP) calibration sites: (Ohp/France, Izana/Spain, and Valladolid/Spain), to establish traceability of the AOD measurements within ACTRIS to the WMO AOD reference. ASP-PMODWRC is going to officially enter CARS in the end of 2023.

WORCC precision filter radiometer (PFR) reference instruments at four locations around Europe

The ASP-PMODWRC aims on standardizing and homogenizing AOD reference scales through the CARS-WORCC common initiative and knowledge exchange on improving calibration and processing algorithms and instrument related measurement long-term consistency.

Main goals:

  • Establish a link among WMO AOD reference scale and ACTRIS/CARS.
  • Creating a permanent cooperation between ACTRIS and WORCC for AOD measurements, calibration and standard operation procedures.

Actions – ACTRIS-CH project objectives:

  • The permanent establishment of WORCC PFR reference instruments at the three main ACTRIS/AERONET sites: (Ohp/France, Tenerife/Spain, Valladolid/Spain).
  • Provide an assessment of AOD differences among CARS ASP-calibration references and WORCC through continuous comparisons and data analysis.
  • Contributing to the quality control of AOD calibrations of ACTRIS national facilities` sun-photometers.
  • Creating links between ACTRIS and WORCC for instrument characterizations, calibration and standard processing AOD procedures.
  • Enhance scientific collaboration among CARS core institutes.
  • Fully incorporate ASP-PMODWRC in CARS.