The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

Abstract

Abstract. The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model version up to 0.01 hPa was used at T42 resolution (~2.8 latitude and longitude) to simulate the lower and middle atmosphere. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. A Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998–2005. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce the Quasi-Biennial Oscillation and major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated accurately, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of interannual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the ECHAM5/MESSy1 model output are available through the internet on request.

Stratospheric aerosol radiative forcing simulated by the chemistry climate model EMAC using aerosol CCI satellite data

“…These contributions were strongly underestimated in Brühl et al (2015) due to a crude parameterization in the used model version based on Jöckel et al (2006). To reproduce the GOMOS 15 observations of extinction at the 3 different wavelengths it is essential to account for dust in a proper way, also with respect to particle size.…”

Assessing the effect of marine isoprene and ship emissions on ozone, using modelling and measurements from the South Atlantic Ocean

“…The EMAC model is a combination of the general circulation model ECHAM5, [18] (version 5.3.01) and the Modular Earth Submodel System [19] (MESSy; version 1.1). The description and evaluation of the model system are presented in, and references therein.…”

Numerical Modeling of Climate-Chemistry Connections: Recent Developments and Future Challenges

“…In the past, SSTs and SIC have been mostly prescribed as boundary conditions damping the climate feedback: an obvious limitation. A valuable option using specific observations of a particular period and region in connection with a CCM is to relax (i.e., nudge) the calculated model dynamics towards real conditions [8,21]; although a nudged CCM (CCMn) is not an ACTM, since the meteorology is "only" relaxed towards observations down to a specific (typically synoptic) scale. A direct confrontation of CCMn results with a specific data set is another possibility to check for instance the performance of the underlying chemistry module: A CCMn can be run successively with two (or more) parameterizations handling the same process (e.g., lightning NO x , deep convection) finding out which approach provides best agreement with the measured data [22][23][24] (see Section 3.1).…”

“…A step forward is therefore the inclusion of more detailed tropospheric chemistry in these CCMs (e.g., considering the non-methane hydrocarbon chemistry); more complex "tropospheric" CCMs are already available and have been, for example, used in connection with investigations related to CMIP (Coupled Model Intercomparison Project; see below) activities. Full chemistry, either in CCMs or AOCCMs, allows more detailed investigations of the interaction of tropospheric and stratospheric chemistry in a changing climate [8]. As a consequence, not only a higher vertical resolution of the upper troposphere/lower stratosphere (UTLS) region is required (nowadays in the order of 1-2 km), but also an enhanced horizontal resolution is necessary (currently about 2-3 degrees latitude/longitude) for an adequate treatment of the dynamical and chemical coupling of the troposphere and the stratosphere including the exchange of air masses.…”

“…As the term "nudging" implies, the Newtonian relaxation technique is used to very weakly force an AGCM or CCM to reproduce the observed sequence of meteorological conditions, but still to calculate its own consistent physics [8,28] and chemistry. This approach enables a direct, point-by-point comparison of model simulation results with in situ and remote sensing observations, similar to ACTM applications, but with a larger uncertainty due to the additional degrees of freedom (in particular sub-grid-scale) of nudged CCMs, which ACTMs usually do not have [29].…”