A three-dimensional simulation of the ozone annual cycle using winds from a data assimilation system

The wind fields from the NASA Goddard stratospheric data assimilation procedure are used in a three-dimensional chemistry and transport model to produce an ozone simulation for the year September 11, 1991 to September 10, 1992. Photochemical production and loss are taken from the Goddard two-dimensional model. The calculated ozone is compared with observations from the total ozone mapping spectrometer (TOMS) on board Nimbus 7 and the microwave limb sounder on the upper atmospheric research satellite. Although the model total ozone is about 50 Dobson units (DU; = 2.69 x 10(-16) molecules cm(-2)) lower than TOMS in the tropics and up to 70 DU higher than TOMS in middle to high latitudes, the simulated ozone fields reproduce many of the features in the observations. Even at the end of this integration, the synoptic features in the modeled total ozone are very similar to TOMS observations, indicating that the model maintains realistic values for the horizontal and vertical gradients, at least in the lower stratosphere. From this good comparison between model and observations on timescales ranging from days to months, we infer that the transport driven by the assimilated wind fields closely approximates the actual atmospheric transport. Therefore the assimilated winds are useful for applications which may be sensitive to the lower stratospheric transport.