Quantitative evaluation of ozone and selected climate parameters in a set of EMAC simulations

• Published in: Geoscientific Model Development
• Main Authors: Righi, Mattia, Eyring, Veronika, Gottschaldt, Klaus-Dirk, Klinger, Carolin, Frank, Franziska, Jöckel, Patrick, Cionni, Irene
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2015
• Subjects: Erdsystem-Modellierung; Sea ice
• Online Access: https://elib.dlr.de/95715/; http://www.geosci-model-dev.net/8/733/2015/gmd-8-733-2015.html

Four simulations with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model have been evaluated with the Earth System Model Validation Tool (ESMValTool) to identify differences in simulated ozone and selected climate parameters that resulted from (i) different setups of the EMAC model (nudged vs. free-running) and (ii) different boundary conditions (emissions, sea surface temperatures (SSTs) and sea-ice concentrations (SICs)). To assess the relative performance of the simulations, quantitative performance metrics are calculated consistently for the climate parameters and ozone. This is important for the interpretation of the evaluation results since biases in climate can impact on biases in chemistry and vice versa. The observational datasets used for the evaluation include ozonesonde and aircraft data, meteorological reanalyses and satellite measurements. The results from a previous EMAC evaluation of a model simulation with weak nudging towards realistic meteorology in the troposphere have been compared to new simulations with different model setups and updated emission datasets in free-running timeslice and nudged Quasi Chemistry-Transport Model (QCTM) mode. The latter two configurations are particularly important for chemistry-climate projections and for the quantification of individual sources (e.g. transport sector) that lead to small chemical perturbations of the climate system, respectively. With the exception of some specific features which are detailed in this study, no large differences that could be related to the different setups of the EMAC simulations (nudged vs. free-running) were found, which offers the possibility to evaluate and improve the overall model with the help of shorter nudged simulations. The main differences between the two setups is a better representation of the tropospheric and stratospheric temperature in the nudged simulations, which also better reproduce stratospheric water vapour concentrations, due to the improved simulation of the temperature in the tropical tropopause layer. ...