Modelling of the interaction between radiation and the atmospheric composition with ICON-ART

Abstract

This thesis presents the modelling of the interaction of radiation and the composition of the Earth's atmosphere with the next generation modelling system ICON-ART. The ICOsahedral Non hydrostatic model with Aerosols and Reactive Trace gases (ICON-ART) provides a suitable environment for atmospheric composition studies on weather and climate time scales. Most global climate models or numerical weather prediction models use simplifications in solving the radiative transfer equation to save computational time. In this thesis, the validation of a more advanced module for solving the radiative transfer equation is presented. This module allows a consistent treatment of the actinic flux calculation and also the radiative net flux calculation. For the first time, photolysis rate calculations are performed with the technique of local grid refinement of ICON. For validation, aircraft campaign data are compared to ICON-ART simulations on a statistical basis. Furthermore, the question on the quantification of the radiative impact of clouds on photolysis rates is addressed. The second part of this thesis focuses on the radiative impact of water vapour and ozone on the atmosphere. Here, AMIP type integrations using a simplified chemistry scheme in conjunction with the climate physics configuration are performed and analysed in comparison to ERA-Interim. Two different simulations are used: The interactive simulation, where modelled ozone is coupled back to the radiation scheme and the non-interactive simulation that uses a default background climatology of ozone. Additionally, a chemical source term for water vapour for the interactive simulation is introduced. For the interactive and non-interactive simulation, the water vapour tape recorder is investigated as a measure of tropical upwelling changes in the atmospheric dynamics. Additionally, the seasonal evolution and latitudinal distribution of age of air is studied. Net flux, calculated with the validated module for photolysis rate calculations is used for shortwave heating rate calculations in a consistent way. The further development of ICON-ART allows for the usage of these calculations in climate integrations. The results for the standard radiation module of ICON are compared to the results of this advanced approach. Changes in the age of air tracer indicate that the ICON-ART model benefits from this development. The improved representation of the stratospheric overturning circulation by interactive heating rate calculations is discussed in the last chapter of this thesis.