This document reports on two validation activities, namely an evaluation of the consistency between the global and regional modelling components of CAMS, focussing on the boundaries of the regional domain, and an evaluation of the regional ensemble and the seven individual models contributing to the ensemble with independent observations, focusing on the concentrations above the surface. The current analysis includes ozone (O3), nitrogen dioxide (NO2), aerosol (PM10/PM2.5/AOD) and carbon monoxide (CO) forecasts covering the period up to May 2020.