VALIDATION OF UARS MICROWAVE LIMB SOUNDER OZONE MEASUREMENT

This paper describes the validation of ozone data from the Upper Atmos phere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz. Analyses described here focus on the MLS Version 3 data (the first set of files made publicly available). We describe results of si mulations performed to assess the quality of the retrieval algorithms, in terms of both mixing ratio and radiance closure. From actual MLS o bservations, the 205-GHz ozone retrievals give better closure (smaller radiance residuals) than that from the 183-GHz measurements and shoul d be considered more accurate from the calibration aspects. However, t he 183-GHz data are less noise limited in the mesosphere and can provi de the most useful scientific results in that region. We compare the r etrieved 205-GHz ozone profiles in the middle-to lower stratosphere to ozonesonde measurements at a wide range of latitudes and seasons. Gro und-based lidar data from Table Mountain, California, provide a good r eference for comparisons at higher altitudes. Based on these analyses, comparisons with balloon-borne measurements and others, as well as a detailed budget of estimated uncertainties, MLS results appear to be g enerally of high quality, with some biases worth mentioning. Results f or the lowermost stratosphere (similar to 50 to 100 hPa) are still in need of improvement. A set of estimated precision and accuracy values is derived for the MLS ozone data sets. We also comment on recent upda tes in the retrieval algorithms and their impact on ozone values.