AN INVESTIGATION INTO THE SOURCE OF THE SPRINGTIME TROPOSPHERIC OZONEMAXIMUM AT MAUNA-LOA-OBSERVATORY

Measurements of CH4, CO, O-3, and H2O vapor from Mauna Loa Observatory (MLO) are examined in conjunction with isentropic trajectories to inv estigate the cause of a maximum in tropospheric O-3 consistently obser ved during spring. CO and O-3 have been found to be positively correla ted in pollution plumes containing O-3 precursors downwind of industri alized regions. However, we report that during continental transport f rom Asia, O-3 is not correlated with either CO or CH4, although CO and CH4 are strongly correlated. The relationship between CO and CH4 sugg ests common source regions. The lack of correlation between these spec ies and O-3 probably indicates an O-3 source distinct from that of CO and CH4. While Asian pollution does not appear to be a strong candidat e for causing the spring increase in O-3, transport characteristics an d H2O vapor measurements are consistent with both an upper-tropospheri c/stratospheric contribution and an enhancement from transport across O-3 gradients.