3:45 PM - 4:00 PM
[AAS06-23] The Importance of Heterogeneous Reaction of NOx and NOy in the Regional Chemical Transport Models for Ozone Simulation
Keywords:ozone, NOx, NOy, heterogeneous reactions, regional chemical transport model
The regional models for simulating ozone pollution have been developed substantially in the last couple of decades, and are now in general thought to reproduce the observational data reasonably well. However, the recent model-intercomparison study in East Asia, MICS-Asia III project, has revealed this is not necessarily true and relatively large discrepancy among models and between model simulation and observational data have been revealed. The purpose of this study is to elucidate the cause of the discrepancies and to propose the revision of regional model simulation for ozone pollution.
So far, model simulation of ozone pollution has been conducted mostly tageting only for O3 and much of efforts have not been made for the reproduction of observational data of key precursors, NOx and VOCs. However, when the model simulation will be used for policy tools in such a way as the future prediction of O3 concentration responding to the emission control of NOx and VOCs, the reproduction of the present concentrations of NOx and VOC are thought to be important in order to improve the reliability of the modelsimulation.
For example, as for NOx the following problems have been pointed out by the comparison between the urban field observation and model simulation.
1. In the uraban atmosphere, HNO3 concentrations are overestimated and NO2 concentrations are underestimated.
2. In the urban atmosphere high concentrations of HONO are observed even in daytime and the formation processes have not been quantified
3. Under high NOx conditions, OH/HO2 concentrations are underestimated.
In the present study, the cause of these phenomena are ascribed to the following heterogeneous reactions of NOx and NOy on aerosol surfaces,
HNO3 + aerosol ---> NO2
NO2 + aerosol ---> HONO
and discussion will be made.
Further, the results of process analysis of vertical and horizontal transport, net chemical production and deposition loss of O3 among models will be made for the simulation results of MICS-Asia III in Beijing and Tokyo.
So far, model simulation of ozone pollution has been conducted mostly tageting only for O3 and much of efforts have not been made for the reproduction of observational data of key precursors, NOx and VOCs. However, when the model simulation will be used for policy tools in such a way as the future prediction of O3 concentration responding to the emission control of NOx and VOCs, the reproduction of the present concentrations of NOx and VOC are thought to be important in order to improve the reliability of the modelsimulation.
For example, as for NOx the following problems have been pointed out by the comparison between the urban field observation and model simulation.
1. In the uraban atmosphere, HNO3 concentrations are overestimated and NO2 concentrations are underestimated.
2. In the urban atmosphere high concentrations of HONO are observed even in daytime and the formation processes have not been quantified
3. Under high NOx conditions, OH/HO2 concentrations are underestimated.
In the present study, the cause of these phenomena are ascribed to the following heterogeneous reactions of NOx and NOy on aerosol surfaces,
HNO3 + aerosol ---> NO2
NO2 + aerosol ---> HONO
and discussion will be made.
Further, the results of process analysis of vertical and horizontal transport, net chemical production and deposition loss of O3 among models will be made for the simulation results of MICS-Asia III in Beijing and Tokyo.