A new interactive chemistry‐climate model: 1. Present‐day climatology and interannual variability of the middle atmosphere using the model and 9 years of HALOE/UARS data

Abstract

[1] The newly developed middle atmosphere general circulation model with interactive photochemistry, Middle Atmosphere European Centre/Hamburg Model 4 with Chemistry (MA-ECHAM4-CHEM), has been applied for several 20 year ''time slice'' experiments using fixed boundary conditions typical of the early and late 1990s, the 1960s, and the near future, including sensitivity runs to study effects of sea surface temperature and greenhouse gas concentration changes. In part 1 we compare the results for the early and late 1990s with 9 years of data of the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite, some presented for the first time, and other satellite and radiosonde data. We show a statistical analysis as well as snapshots of a set of chemical species for typical situations. The model captures the main features of temperature and ozone distributions including the interannual variability of the Arctic and Antarctic vortices and homogeneous and heterogeneous ozone destruction. A detailed comparison of modeled and observed chlorine and nitrogen species including denitrification and chlorine repartitioning in the polar vortices is presented, showing generally good agreement. This holds also for chemical ozone budgets derived from the model and from satellite data. Computed stratospheric and mesospheric water vapor agrees with the satellite data within about 10%, including dehydration in the Antarctic winter. However, in the tropical lower stratosphere, the concentrations of the source gases are underestimated, presumably because of numerical deficiencies in transport. It is shown that interactive photochemistry is important to get agreement with observed temperatures in the lower stratosphere in highlatitude spring. Our coupled model provides a powerful tool to investigate chemicalradiative-dynamical feedback mechanisms of anthropogenic trace gas emissions and natural variability on climate and stratospheric ozone, at least for quasi-steady-state conditions.INDEX TERMS: 0340 Atmospheric Composition and Structure: Middle atmospherecomposition and chemistry; 0341 Atmospheric Composition and Structure: Middle atmosphere-constituent transport and chemistry (3334); 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation; 3319 Meteorology and Atmospheric Dynamics: General circulation; KEYWORDS: chemistryclimate model, stratospheric ozone, UARS satellite data, chlorine partitioning, polar ozone Citation: Steil, B., C. Brühl, E. Manzini, P. J. Crutzen, J. Lelieveld, P. J. Rasch, E. Roeckner, and K. Krüger, A new interactive chemistry-climate model: 1. Present-day climatology and interannual variability of the middle atmosphere using the model and 9 years of HALOE/UARS data,

Climatology and Forcing of the Quasi-Biennial Oscillation in the MAECHAM5 Model

“…The improvement in the annual mean upwelling, as described here, may become more relevant in chemistry climate models, where biases in the tropical upwelling, as presented here for CL39, must have negative impacts on the vertical transport of source gases like methane or nitrous oxide (Steil et al 2003).…”

Initial fate of fine ash and sulfur from large volcanic eruptions

“…black carbon, organic carbon, sea salt, dust) were ignored. Sulfur chemistry is calculated in the troposphere as described in Feichter et al (1996), and in the stratosphere as in Hommel (2008) and Steil et al (2003). Climatological concentrations of background OH values have been taken from Timmreck et al (2003), other gas-phase species from Jöckel et al (2005).…”

Interannual variation patterns of total ozone and lower stratospheric temperature in observations and model simulations

“…Climatologies and trends from stratospheric "chemistryclimate models" are realistic and have been validated Austin et al, 2003;Manzini et al, 2003;Steil et al, 2003). The purpose of this study is to extend this climatological validation to the comparison of interannual variation patterns.…”