Validation of Aura Microwave Limb Sounder O ₃ and CO observations in the upper troposphere and lower stratosphere

Global satellite observations of ozone and carbon monoxide from the Microwave Limb Sounder (MLS) on the EOS Aura spacecraft are discussed with emphasis on those observations in the 215–100 hPa region (the upper troposphere and lower stratosphere). The precision, resolution and accuracy of the data produced by the MLS “version 2.2” processing algorithms are discussed and quantified. O 3 accuracy is estimated at ∼40 ppbv +5% (∼20 ppbv +20% at 215 hPa) while the CO accuracy is estimated at ∼30 ppbv +30% for pressures of 147 hPa and less. Comparisons with expectations and other observations show good agreements for the O 3 product, generally consistent with the systematic errors quoted above. In the case of CO, a persistent factor of ∼2 high bias is seen at 215 hPa. However, the morphology is shown to be realistic, consistent with raw MLS radiance data, and useful for scientific study. The MLS CO data at higher altitudes are shown to be consistent with other observations.