Evaluation of CLaMS, KASIMA and ECHAM5/MESSy1 simulations in the lower stratosphere using observations of Odin/SMR and ILAS/ILAS-II

摘要

1-year data sets of monthly averaged nitrous oxide (N₂O) and ozone (O₃)derived from satellite measurements were used as a tool for the evaluation ofatmospheric photochemical models. Two 1-year data sets, one solar occultationdata set derived from the Improved Limb Atmospheric Spectrometer (ILAS and ILAS-II)and one limb sounding data set derived from the Odin Sub-Millimetre Radiometer(Odin/SMR) were employed. Here, these data sets are used for the evaluationof two Chemical Transport Models (CTMs), the Karlsruhe Simulation Model ofthe Middle Atmosphere (KASIMA) and the Chemical Lagrangian Model of theStratosphere (CLaMS) as well as for one Chemistry-Climate Model (CCM),the atmospheric chemistry general circulation model ECHAM5/MESSy1 (E5M1)in the lower stratosphere with focus on the Northern Hemisphere. Since theOdin/SMR measurements cover the entire hemisphere, the evaluation is performedfor the entire hemisphere as well as for the low latitudes, midlatitudes andhigh latitudes using the Odin/SMR 1-year data set as reference. To assess theimpact of using different data sets for such an evaluation study we repeatthe evaluation for the polar lower stratosphere using the ILAS/ILAS-II data set.Only small differences were found using ILAS/ILAS-II instead of Odin/SMR as areference, thus, showing that the results are not influenced by the particularsatellite data set used for the evaluation. The evaluation of CLaMS, KASIMAand E5M1 shows that all models are in agreement with Odin/SMR and ILAS/ILAS-II.Differences are generally in the range of ±20%. Larger differences (upto −40%) are found in all models at 500±25 K for N₂O mixing ratiosgreater than 200 ppbv, thus in air masses of tropical character. Generally,the largest differences were found for the tropics and the lowest for thepolar regions. However, an underestimation of polar winter ozone loss wasfound both in KASIMA and E5M1 both in the Northern and Southern Hemisphere.