Enhanced operational methods in the NOAA Umkehr ground-based network for the future OMPS validation.

This work evaluates the quality of stratospheric and tropospheric ozone information derived from the ground- based Dobson and Brewer measurements. The updated and homogenized SBUV/2 V8 ozone profile time series is evaluated for internal consistency and potential drifts between different satellites. Long-term records from well-maintained Dobson Umkehr stations are used for assessment of the SBUV time series. The Umkehr technique for producing a vertical ozone profile by ground-based observations of the Umkehr effect is well known. However, observations of the Umkehr effect by co-located Dobson and Brewer spectrophotometers yield slightly different results, which are also dependent on total ozone values. These differences make it difficult to compare ozone profiles between stations. Statistical methods can be used to adjust measurements of a specific instrument to those of a reference instrument and produce more coherent data sets, but they fail to explain the cause of the differences. They also require intercomparisons at various total ozone amounts to define the parameters. Our recent investigations suggest that differences are due to the effects of stray light within the instruments and can be corrected by including a stray light parameter in each instrument's characterization. Here we present some resulting changes to retrieved ozone profiles along with their implications for observational methods, and for completeness of the existing data sets. The NOAA Earth Systems Research Lab has a number of capabilities and extensive experience with the ground- based ozone measurements that will be useful for the Ozone Mapping and Profiler Suite (OMPS) products under the NPOESS validation program. We plan to provide regular ozone profiles derived from the NOAA- operated and calibrated Dobson and Brewer instruments that are also an integral part of the US and international ozone monitoring networks.