Tropical Atlantic Ozone Paradox Resolved

During January and February of 2005, TES made a series of Special Observations which helped to clarify a long-standing difference between the observations of O3 and O3 columns made by balloons and in-situ sensors, and the previous satellite view of the tropospheric ozone over the tropical Atlantic. Prior to TES, the satellite view of tropical tropospheric O3 columns (TTOCs) for this region between the months of December and February indicated that TTOC was highest over the southern tropical Atlantic, even though the major source for tropospheric O3 at this time is the northern African biomass burning. This discrepancy between satellite and in-situ O3 observations and models came to be known as the “Tropical Atlantic Ozone Paradox” -- so-called because satellite UV O3 column instruments are unable to measure the same enhanced O3 during the N. Africa biomass burning season that is predicted by models and measured by ground and aircraft based instruments.

TES made a series of Step & Stare measurements of tropospheric O3 source and sink regions, which provide denser nadir coverage than the Global Survey, allowing TES to better characterize the extent of pollution outflow events. TES observations show an elevated O3 layer north of the equator in the mid-troposphere (at 600 hPa), corresponding to the Hartmattan winds, which bring biomass emissions and dust off the Sahara. For the first time, elevated O3 in the lower troposphere was directly measured for 0 – 10° N latittude, over the tropical Atlantic Ocean. Trajectory analyses and a sensitivity study using the GEOS-Chem model confirmed the influence of the northern Africa biomass burning on the elevated O3 mixing ratios observed by TES. Read the full text (PDF, 1.2 MB) of the published paper.

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