Optimisation of CHIMERE configuration in the frame of an ozone sensitivity study Fanny Lasry, Isabelle Coll CHIMERE workshop 21 – 22 March 2005

Problematic Ozone: harmful pollutant - respiratory troubles - yield decrease Study focused on the Berre-Marseilles area (South of France), frame of the ESCOMPTE program Urban area Industrial area  Diversity of the emitters => variety of primary compounds  Coastal site => small scale phenomena such as sea-breeze Action engaged in order to reduce ozone concentrations in the troposphere (Göteborg protocol) Efficiency of these measures on ozone concentrations?

Strategy Research of an optimized configuration of CHIMERE in order to simulate ozone episodes in such a complex area  Small scale dynamic (sea breeze phenomenon)  Variety of the emitted compounds Characteristics of the regionModel configuration Dynamical fields ECMWF (0.5°) -> RAMS, MM5 (3km) Emission inventory GENEMIS -> ESCOMPTE Chemical mechanism MELCHIOR (44 species) -> SAPRC (80 species)

SAPRC99 (Carter) “A detailed mechanism for the gas-phase atmospheric reactions of VOCs and NOx in urban and regional atmospheres” (documentation of the SAPRC99 chemical mechanism for VOC reactivity assessment, Carter, 2000) -Used to “determine the absolute and relative ozone impact of the many types of VOCs that can be emitted into the atmosphere, and for other control strategy and research applications” -Used to calculate the various ozone reactivity scales developed by Carter (MIR, 1994) 82 species – 30 VOCs 241 reactions Representation of the radicals chemistry Detailed speciation of VOCs and RO2 Implantation in CHIMERE

Impact of a better resolved dynamic on ozone fields Boundary layer better resolved Better restitution of the sea breeze – wind fields perpendicular to the coast ECMWF (0.5°)MM5 (3km) Boundary layer height

ECMWF RAMS Model overestimation MM5 Impact of a better resolved dynamic on ozone fields Bias on maximal values

GENEMIS NOx VOC Higher Nox emissions in town Higher biogenic VOCs emissions ESCOMPTE Impact of a more accurate emission inventory on ozone fields

GENEMIS ESCOMPTE Better restitution of the diurnal cycle of ozone: - Better titration by the NOx at night - Increase of ozone maximal values up to 10 ppb locally Better restitution of primary compounds levels, especially in urban areas Impact of a more accurate emission inventory on ozone fields

MM5+ESC+MELCHIOR MM5+ESC+SAPRC Overestimation of ozone maximal values with MELCHIOR: too productive? SAPRC: better scores, less false alert Impact of the chemical mechanism on ozone fields Missed alertCorrect alertFalse alert Success index – 90ppb threshold

Initial configuration ECMWF+GENEMIS+MELCHIOR Scenario configuration MM5+PRIMEQUAL+SAPRC Final configuration MM5+ESCOMPTE+SAPRC

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