An operational meteorology and air quality forecasting system is currently under development by the Environmental
Research Laboratory of NCSR “Demokritos”. The system is based on the meteorological model MM5, the in-house EMISLAB
emissions processing system and the chemical transport model CMAQ. It is configured to apply on the Greater Athens Area with a
4-domains nested configuration focusing on a high spatial resolution (1x1 km2) inner domain. The system produces meteorological
and air quality predictions for a 72-hours time horizon with 1 hour time step. This paper uses the output of the operational system to
apply the CMAQ adjoint for ozone sensitivity calculations, focusing for the two days of 18 and 19 July 2005.
In the current study, the calculated ground level ozone concentrations at certain defined locations and times are considered as the “response functional”. Sensitivities of the response functional with respect to the state variables (species concentrations on the grid
points and species emissions, e.g., NOX, CO, VOCs) are calculated by running the adjoint model backwards in time (reverse mode).
The distribution of the sensitivities in the computational domain, obtained for different times, provides essential information for the
analysis: isosurfaces of sensitivities delineate influence regions, i.e., areas where perturbations in some concentrations will result in
significant changes in the ozone concentrations in the area of interest at the final time
