Role of meteorological variability in global tropospheric ozone during 1970-2008

Interannual variation in global tropospheric ozone associated with meteorological variability is characterized in this study using a global chemical transport model CHASER. We focus on five meteorological variability: El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Arctic Oscillation (AO), Hadley, and monsoon circulations. Results show that the anomaly in tropospheric column ozone (TCO) is positive (1-1.5 DU) in the western Pacific including Indonesia and negative (-2.5 DU) in the eastern Pacific in October-November-December (OND) during positive phase of ENSO. The model exhibits TCO increase (0.5-1.5 DU) in the central to eastern Pacific over the subtropics. During the positive phase of IOD, the model shows TCO increase (1.5-2 DU) in the west of 90 degrees E with a decrease (1-1.5 DU) in the east. Intensified Hadley circulation causes TCO increase (0.8 DU) in North America in DJF. Intensified monsoon circulation enhances TCO (1.2 DU) in the western Indian Ocean. During positive phase of AO, TCO is decreased (1 DU) in the high northern latitudes. The contribution of meteorological variability to total interannual variation in global and regional TCO is also quantified in this study. The results suggest that interannual variation of TCO in the tropics and high northern latitudes are generally explainable by ENSO, IOD, AO, and interannual variation in Hadley and monsoon circulations. ENSO explains 79% of the variance in the tropical eastern Pacific in OND. AO explains 72% of the variance in the high northern latitudes in DJF.