| Summary: | The spatial and temporal variations in tropospheric ozone over North America from the 1970s to 2000s are studied using the newly developed Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST) and the ozonesonde data. The variations in the lower, middle, and upper troposphere are examined in long-term, by decade and season. Throughout the decades, the highest ozone concentrations generally appeared over central mid-latitudes of North America in the lower and middle troposphere, while in the upper troposphere, high concentrations appeared over the Arctic. The overall ozone trends in the four decades averaged over the North America are positive, increasing with altitude. TOST is compared with the ozonesonde data at selected stations and both datasets correlate closely, stronger in high latitudes. TOST is resolved in latitude, longitude, and altitude so new insights gained from this study on the variations of tropopsheric ozone in these dimensions are particularly valuable. M.Sc.
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