Ghassan Taha

Ozone profiles in the high-latitude stratosphere and lower mesosphere measured by the Improved Limb Atmospheric Spectrometer (ILAS)-II: comparison with other satellite sensors and ozonesondes

A solar occultation sensor, the Improved Limb Atmospheric Spectrometer (ILAS)-II, measured 5890 vertical profiles of ozone concentrations in the stratosphere and lower mesosphere and of other species from January to October 2003. The measurement latitude coverage was 54–71°N and 64–88°S, which is similar to the coverage of ILAS (November 1996 to June 1997). One purpose of the ILAS-II measurements was to continue such high-latitude measurements of ozone and its related chemical species in order to help accurately determine their trends. The present paper assesses the quality of ozone data in the version 1.4 retrieval algorithm, through comparisons with results obtained from comprehensive ozonesonde measurements and four satellite-borne solar occultation sensors. In the Northern Hemisphere (NH), the ILAS-II ozone data agree with the other data within ±10% (in terms of the absolute difference divided by its mean value) at altitudes between 11 and 40 km, with the median coincident ILAS-II profiles being systematically up to 10% higher below 20 km and up to 10% lower between 21 and 40 km after screening possible suspicious retrievals. Above 41 km, the negative bias between the NH ILAS-II ozone data and the other data increases with increasing altitude and reaches 30% at 61–65 km. In the Southern Hemisphere, the ILAS-II ozone data agree with the other data within ±10% in the altitude range of 11–60 km, with the median coincident profiles being on average up to 10% higher below 20 km and up to 10% lower above 20 km. Considering the accuracy of the other data used for this comparative study, the version 1.4 ozone data are suitably used for quantitative analyses in the high-latitude stratosphere in both the Northern and Southern Hemisphere and in the lower mesosphere in the Southern Hemisphere.

Data analysis and retrieval algorithms for the Ozone Mapping and Profiler Suite / Limb Profiler instrument

Three candidate algorithms for the retrieval of ozone profile for the NPP OMPS Limb Profiler are described. The first one relies on the well established Doublet/Triplet method coupled with Optimal Estimation. The second one performs spectral fitting and uses Multiple Linear Regression. The last one is a direct application of the Optimal Estimation method on the actual CCD array measurements. The fundamentals of each technique are reviewed and their advantages/disadvantages are discussed. Sample results are given to illustrate the performance of each method.

The OMPS Limb Profiler instrument: An alternative data analysis and retrieval algorithm

An alternative algorithm is being analyzed to retrieve ozone and aerosol vertical distribution information from the OMPS/LP sensor which will be manifested on the upcoming NPOESS Preparatory Project (NPP) platform in early 2011. The algorithm relies on the optimal estimation method to infer ozone density and aerosol extinction directly from the radiance measurements made by the ensemble of CCD array pixels. The fundamentals of the technique are reviewed and the advantages of the method with respect to the mainstream retrieval algorithm are discussed. Sample results are given to illustrate the performance of the new method.