Study of stratospheric composition using airborne submillimeter radiometry and a chemical transport model

Abstract

The Airborne Submillimeter Radiometer (ASUR) was deployed aboard the Falcon research aircraft during the SCIAVALUE (SCIAMACHY - Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY - Validation Utilization Experiment), the EUPLEX (European Polar and Lee wave Experiment), and the PAVE (Polar Aura Validation Experiment) campaigns. An impressive array of microwave measurements of O3, N2O, HCl, HNO3 and ClO is amassed during the missions from the tropics to the Arctic in various seasons.Using the data various satellite sensor measurements for different molecules are validated. In addition, a new model, the Bremen Chemical Transport Model (CTMB), is introduced. Evaluation of the Linearized ozone chemistry shows that the ozone profiles simulated with the Linoz model are accurate enough to be used for stratospheric chemistry and transport studies though the simulations show a low bias of about 9% in the middle stratosphere and a high bias of 10-30% in the lower and upper stratosphere, depending on altitude. The simulations for various years suggest that the N2O and NOy calculations depend greatly on the accuracy of the meteorological analyses used in the model. The simulations reveal that the N2O VMRs calculated with the parameterized chemistry are slightly smaller in the lower stratosphere. The inaccuracies in the wind analyses and in the model transport and uncertainties in the chemical reaction rates can be the reasons for the lower values. The N2O-NOy coupled chemistry is in good shape and the transport barriers are reasonably represented in the model. The comparison among the ASUR, the SLIMCAT and the CTMB profiles reveal the upper stratospheric ozone deficit in the SLIMCAT calculations. The comparisons also indicate that the transport process in the models is still to be improved.