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

Abstract

Abstract. 1-year data sets of monthly averaged nitrous oxide (N 2 O) and ozone (O 3 ) derived from satellite measurements were used as a tool for the evaluation of atmospheric photochemical models. Two 1-year data sets, one solar occultation data 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 evaluation of two Chemical Transport Models (CTMs), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and the Chemical Lagrangian Model of the Stratosphere (CLaMS) as well as for one ChemistryClimate Model (CCM), the atmospheric chemistry general circulation model ECHAM5/MESSy1 (E5M1) in the lower stratosphere with focus on the Northern Hemisphere. Since the Odin/SMR measurements cover the entire hemisphere, the evaluation is performed for the entire hemisphere as well as for the low latitudes, midlatitudes and high latitudes using the Odin/SMR 1-year data set as reference. To assess the impact of using different data sets for such an evaluation study we repeat the 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 a reference, thus, showing that the results are not influenced by the particular satellite data set used for the evaluation. The evaluCorrespondence to: F. Khosrawi (farah@misu.su.se) ation of CLaMS, KASIMA and 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 (up to −40%) are found in all models at 500±25 K for N 2 O mixing ratios greater than 200 ppbv, thus in air masses of tropical character. Generally, the largest differences were found for the tropics and the lowest for the polar regions. However, an underestimation of polar winter ozone loss was found both in KASIMA and E5M1 both in the Northern and Southern Hemisphere.

Denitrification, dehydration and ozone loss during the 2015/2016 Arctic winter

“…The former reason, however, is more likely, since a well-known feature in EMAC is that the downward transport is underestimated in the lower parts of the polar vortices (Brühl et al, 2007), despite the model vorticity and divergence fields being nudged towards ECMWF analysis. Further, ozone loss in EMAC is rather underestimated than overestimated as was found in the evaluation study by Khosrawi et al (2009).…”

Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

“…The cause of these differences may be related to model dynamics. In fact, a well-known feature in EMAC is that downward transport is underestimated in the lower parts of the polar vortices (Brühl et al, 2007;Khosrawi et al, 2009), despite the model vorticity and divergence fields being nudged towards ECMWF ERA-Interim reanalyses. Further, as was discussed by Brühl et al (2007), a too-tight subtropical barrier causing too-low N 2 O and toohigh NO y in the middle stratosphere is simulated by EMAC.…”

“…In fact, an already-known feature in EMAC is that the downward transport is underestimated (Brühl et al, 2007;Khosrawi et al, 2009). Figure 9 shows the temporal evolution of temperature and HNO 3 from EMAC, Envisat/MIPAS, and Aura/MLS for the Arctic winter 2010/2011 (December 2010 to April 2011) at high latitudes (70-90 • N) as a function of pressure.…”

Assessment of the interannual variability and influence of the QBO and upwelling on tracer–tracer distributions of N2O and O3 in the tropical lower stratosphere

“…In a recent model evaluation study (Khosrawi et al, 2009), a method was used based on O 3 and N 2 O measurements to evaluate two CTMs and one CCM in the lower stratosphere. In this method, monthly averages of O 3 and N 2 O, binned by potential temperature, are calculated in the N 2 O/O 3 tracer space.…”

“…In this method, monthly averages of O 3 and N 2 O, binned by potential temperature, are calculated in the N 2 O/O 3 tracer space. The method applied in Khosrawi et al (2009) was introduced by Proffitt et al (2003) for the Northern Hemisphere lower stratosphere and based on aircraft and balloonborne measurements. This type of analysis helps to separate O 3 variability due to latitudinal transport from photochemical changes.…”