The Aerosol Direct Radiative Impact Experiment (ADRIEX) was a joint UK Met Office/Natural Environment Research Council (NERC)/UK Royal Society/University of Oslo project aiming at improving our understanding of the radiative effects of anthropogenic aerosol and gases (ozone and methane) in the troposphere. This dataset contains NOx outputs from the TOMCAT model. “Chemical attributes” are found by interpolating chemical distributions (in space and time) from a global chemical transport model to the origin of each trajectory (using its full length). During the ICARTT campaign the TOMCAT global CTM is being run in near-real time (about 19 hours behind present) driven by wind analyses from the ECMWF. The back trajectories are sufficiently long that a TOMCAT chemical analysis exists even at the origin of forecast trajectories. For example, the longest forecast lead time for the Azores domain is 5 days but the back trajectories are 7 days long so that the TOMCAT fields dating from 2 days before the latest meteorological analysis are used to find the attributes. For the US East Coast domain the back trajectories are shorter (3 days long) but the longest lead time is also 3 days so that the chemical attributes can be calculated as soon as TOMCAT has been brought up to date with the latest ECMWF analyses.

This dataset contains monthly mean ozone output between 1979-2016 simulated by the TOMCAT/SLIMCAT model. The data contains ozone and a passive odd-oxygen tracer that is set equal to the modelled chemical Ox =O(3 P)+O(1 D)+ O3 concentration on the first day every year and then advected passively without chemistry. It was simulated using the TOMCAT/SLIMCAT three-dimensional offline chemical transport model, using σ-p vertical coordinates and identical stratospheric chemistry and aerosol loading, solar flux input and surface mixing ratios of long-lived source gases. The long-term simulation (1979-2016) was performed with a T42 horizontal resolution of approximately 2.8° latitude × 2.8° longitude and 32 levels from the surface to 60 km. The model uses horizontal winds and temperature from the reanalysis data of the European Centre for Medium-Range Weather Forecasts. The TOMCAT/SLIMCAT model contains a detailed description of the distribution of chemical species for the troposphere and stratosphere including heterogeneous reactions on sulfate aerosols and liquid/solid polar stratospheric clouds either with a simple or full microphysical PSC scheme, as well as chemistry reactions of the oxygen, nitrogen, hydrogen, chlorine and bromine families. The model uses a hybrid σ-p or σ-θ vertical coordinate and has an option to run at different horizontal resolution forced by different meteorological reanalysis. Tracer transport uses the conservation of the second order moments scheme of Prather. Vertical advection is calculated from the divergence of the horizontal mass flux.