In November 2019, an intercomparison campaign and a scientific workshop took place at Izaña Observatory involving different types of photometric observations utilising different techniques. The comparison project consisted in a 1-yr field campaign at the Izaña Observatory involving Brewer, EKO MS-711, PFR and Cimel operational photometric measurements as well as AOD measurements performed by means of FTIR (not operational and product under validation). Izaña provided also in situ aerosol measurements, lidar and meterological measurements as ancillary data. This comparison project is within the WMO strategies, which follows a multi-platform approach with the goal of ensuring a global homogenization of the current photometric observing networks, important for satellite calibration/validation and model assimilation/validation.

This campaign is also within the future scope of the EMPIR and ACTRIS/CARS projects.

Figure 1.- PREDE instrument deployed in Izaña Observatory for the intercomparison project.

A Prede sun photometer, the reference instrument in the SKYNET network, was installed at IZO as a collaboration between IARC/AEMET, the Italian National Research Council and the University of Valencia (Spain). Private companies such as Cimel Electronique also collaborated in this project from a scientific point of view. The University of Valladolid provided Caelis as a common platform for this multi-instrument comparison.