Assimilation of MLS ozone measurements in the global three-dimensional chemistry transport model ROSE

A method for assimilating observations of ozone was implemented in the thre e-dimensional global stratospheric chemistry transport model ROSE. The mode l contains an extensive photochemical scheme which includes heterogeneous c hemistry and uses temperature and wind fields from the UKMO (United Kingdom Meteorological Office) stratospheric analysis. Ozone measurements obtained by the Microwave Limb Sounder (MLS) on board th e Upper Atmosphere Research Satellite (UARS) were assimilated in the model using the sequential statistical interpolation approach. The analysis is pe rformed using a time invariant background error covariance matrix that only includes horizontal covariances. Results from a sixty day simulation are p resented and it is shown that assimilation of the MLS observations results in improved global three-dimensional distributions of ozone as seen from co mparisons with MLS data not assimilated in the model. For further validatio n, the stratospheric total ozone fields computed from the analysis are comp ared with the TOVS total ozone measurements and it is shown that they agree within the uncertainty of the data.