Distribution of Tropical Tropospheric Ozone Determined by the Scan-Angle Method Applied to TOMS Measurements

This work describes the first method to determine the tropical tropospheric ozone column directly from the Total Ozone Mapping Spectrometer (TOMS) space-borne instrument based on the physical differences in ozonecolumn detection as a function of its scan-angle geometry. Comparisons to tropical ozonesonde observations suggest the accuracy of these retrievals is ;20%. Tropospheric ozone derived from this scan-angle method (SAM) exhibits a broad enhancement over South America, the southern Atlantic Ocean, and western South Africa and a minimum over the central Pacific Ocean in September–October. An ozone enhancement in equatorial North Africa is seen in March, the northern burning season. This ozone abundance is not detected by other retrieval methods. The magnitude of the ozone enhancement south of the equator is greater than the enhancement north of the equator. Abnormally high tropospheric ozone occurs over the western Pacific Ocean during the El Niño season when the ozone amounts are as high as those over Africa.